Manhattan Project

Manhattan Project

Overview
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. From 1942 to 1946, the project was under the direction of Major General
Major general (United States)
In the United States Army, United States Marine Corps, and United States Air Force, major general is a two-star general-officer rank, with the pay grade of O-8. Major general ranks above brigadier general and below lieutenant general...

 Leslie Groves
Leslie Groves
Lieutenant General Leslie Richard Groves, Jr. was a United States Army Corps of Engineers officer who oversaw the construction of the Pentagon and directed the Manhattan Project that developed the atomic bomb during World War II. As the son of a United States Army chaplain, Groves lived at a...

 of the US Army Corps of Engineers. The Army component of the project was designated the Manhattan District; "Manhattan" gradually superseded the official codename, "Development of Substitute Materials", for the entire project.
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Encyclopedia
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. From 1942 to 1946, the project was under the direction of Major General
Major general (United States)
In the United States Army, United States Marine Corps, and United States Air Force, major general is a two-star general-officer rank, with the pay grade of O-8. Major general ranks above brigadier general and below lieutenant general...

 Leslie Groves
Leslie Groves
Lieutenant General Leslie Richard Groves, Jr. was a United States Army Corps of Engineers officer who oversaw the construction of the Pentagon and directed the Manhattan Project that developed the atomic bomb during World War II. As the son of a United States Army chaplain, Groves lived at a...

 of the US Army Corps of Engineers. The Army component of the project was designated the Manhattan District; "Manhattan" gradually superseded the official codename, "Development of Substitute Materials", for the entire project. Along the way, the Manhattan Project absorbed its earlier British counterpart, Tube Alloys
Tube Alloys
Tube Alloys was the code-name for the British nuclear weapon directorate during World War II, when the development of nuclear weapons was kept at such a high level of secrecy that it had to be referred to by code even in the highest circles of government...

.

The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion (roughly equivalent to $ as of 20). Over 90% of the cost was for building factories and producing the fissionable materials, with less than 10% for development and production of the weapons. Research and production took place at more than 30 sites, some secret, across the United States, the United Kingdom and Canada. Two types of atomic bomb were developed during the war. A relatively simple gun-type fission weapon
Gun-type fission weapon
Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the "gun" method: shooting one piece of sub-critical material into another...

 was made using uranium-235
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...

, an isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 that makes up only 0.7 percent of natural uranium. Since it is chemically identical to the main isotope, uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...

, and has almost the same mass, it proved difficult to separate. Three methods were employed for uranium enrichment: electromagnetic
Calutron
A calutron is a mass spectrometer used for separating the isotopes of uranium. It was developed by Ernest O. Lawrence during the Manhattan Project and was similar to the cyclotron invented by Lawrence. Its name is a concatenation of Cal. U.-tron, in tribute to the University of California,...

, gaseous
Gaseous diffusion
Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride through semi-permeable membranes. This produces a slight separation between the molecules containing uranium-235 and uranium-238 . By use of a large cascade of many stages, high separations...

 and thermal
Thermophoresis
Thermophoresis, thermodiffusion, or Soret effect , is a phenomenon observed when a mixture of two or more types of motile particles are subjected to the force of a temperature gradient and the different types of particles respond to it differently. The term "Soret effect" normally means...

. Most of this work was performed at Oak Ridge, Tennessee
Oak Ridge, Tennessee
Oak Ridge is a city in Anderson and Roane counties in the eastern part of the U.S. state of Tennessee, about west of Knoxville. Oak Ridge's population was 27,387 at the 2000 census...

.

In parallel with the work on uranium was an effort to produce plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

. Reactors were constructed at Hanford, Washington
Hanford Site
The Hanford Site is a mostly decommissioned nuclear production complex on the Columbia River in the U.S. state of Washington, operated by the United States federal government. The site has been known by many names, including Hanford Works, Hanford Engineer Works or HEW, Hanford Nuclear Reservation...

, in which uranium was irradiated and transmuted
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...

 into plutonium. The plutonium was then chemically separated from the uranium. The gun-type design proved impractical to use with plutonium so a more complex implosion-type weapon was developed in a concerted design and construction effort at the project's weapons research and design laboratory in Los Alamos, New Mexico
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...

. The first nuclear device ever detonated was an implosion-type bomb at the Trinity test
Trinity test
Trinity was the code name of the first test of a nuclear weapon. This test was conducted by the United States Army on July 16, 1945, in the Jornada del Muerto desert about 35 miles southeast of Socorro, New Mexico, at the new White Sands Proving Ground, which incorporated the Alamogordo Bombing...

, conducted at New Mexico's Alamogordo Bombing and Gunnery Range
White Sands Missile Range
White Sands Missile Range is a rocket range of almost in parts of five counties in southern New Mexico. The largest military installation in the United States, WSMR includes the and the WSMR Otera Mesa bombing range...

 on 16 July 1945. Little Boy
Little Boy
"Little Boy" was the codename of the atomic bomb dropped on Hiroshima on August 6, 1945 by the Boeing B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets of the 393rd Bombardment Squadron, Heavy, of the United States Army Air Forces. It was the first atomic bomb to be used as a weapon...

, a gun-type weapon, and the implosion-type Fat Man
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...

 were used in the atomic bombings of Hiroshima and Nagasaki
Atomic bombings of Hiroshima and Nagasaki
During the final stages of World War II in 1945, the United States conducted two atomic bombings against the cities of Hiroshima and Nagasaki in Japan, the first on August 6, 1945, and the second on August 9, 1945. These two events are the only use of nuclear weapons in war to date.For six months...

, respectively.

The Manhattan Project operated under a blanket of tight security, but Soviet atomic spies
Atomic Spies
Atomic Spies and Atom Spies are terms that refer to various people in the United States, Great Britain, and Canada who are thought to have illicitly given information about nuclear weapons production or design to the Soviet Union during World War II and the early Cold War...

 still penetrated the program. It was also charged with gathering intelligence on the German nuclear energy project
German nuclear energy project
The German nuclear energy project, , was an attempted clandestine scientific effort led by Germany to develop and produce the atomic weapons during the events involving the World War II...

. Through Operation Alsos
Operation Alsos
Operation Alsos was an effort at the end of World War II by the Allies , branched off from the Manhattan Project, to investigate the German nuclear energy project, seize German nuclear resources, materials and personnel to further American research and to prevent their capture by the Soviets, and...

, Manhattan Project personnel served in Europe, sometimes behind enemy lines, where they gathered nuclear materials and rounded up German scientists. In the immediate postwar years the Manhattan Project conducted weapons testing at Bikini Atoll
Bikini Atoll
Bikini Atoll is an atoll, listed as a World Heritage Site, in the Micronesian Islands of the Pacific Ocean, part of Republic of the Marshall Islands....

 as part of Operation Crossroads
Operation Crossroads
Operation Crossroads was a series of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. It was the first test of a nuclear weapon after the Trinity nuclear test in July 1945...

, developed new weapons, promoted the development of the network of national laboratories
United States Department of Energy National Laboratories
The United States Department of Energy National Laboratories and Technology Centers are a system of facilities and laboratories overseen by the United States Department of Energy for the purpose of advancing science and helping promote the economic and defensive national interests of the United...

, supported medical research into radiology
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...

 and laid the foundations for the nuclear navy
Nuclear navy
Nuclear navy, or nuclear powered navy consists of ships powered by relatively small onboard nuclear reactors known as naval reactors. The concept was revolutionary for naval warfare when first proposed, as it meant that these vessels did not need to stop for fuel like their conventional...

. It maintained control over American atomic weapons research and production until the formation of the United States Atomic Energy Commission
United States Atomic Energy Commission
The United States Atomic Energy Commission was an agency of the United States government established after World War II by Congress to foster and control the peace time development of atomic science and technology. President Harry S...

 in January 1947.

Origins


In August 1939, prominent physicists Leó Szilárd
Leó Szilárd
Leó Szilárd was an Austro-Hungarian physicist and inventor who conceived the nuclear chain reaction in 1933, patented the idea of a nuclear reactor with Enrico Fermi, and in late 1939 wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project that built the atomic bomb...

 and Eugene Wigner drafted the Einstein–Szilárd letter, which warned of the potential development of "extremely powerful bombs of a new type". It urged the United States to take steps to acquire stockpiles of uranium ore and accelerate the research of Enrico Fermi
Enrico Fermi
Enrico Fermi was an Italian-born, naturalized American physicist particularly known for his work on the development of the first nuclear reactor, Chicago Pile-1, and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics...

 and others into nuclear chain reaction
Nuclear chain reaction
A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. The specific nuclear reaction may be the fission of heavy isotopes or the fusion of light isotopes...

s. They had it signed by Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...

 and delivered to President
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....

 Franklin Roosevelt. Roosevelt called on Lyman Briggs of the National Bureau of Standards to head the Advisory Committee on Uranium
S-1 Uranium Committee
The S-1 Uranium Committee was a Committee of the National Defense Research Committee that succeeded the Briggs Advisory Committee on Uranium and later evolved into the Manhattan Project.- World War II begins :...

 to investigate the issues raised by the letter. Briggs held a meeting on 21 October 1939, which was attended by Szilárd, Wigner and Edward Teller
Edward Teller
Edward Teller was a Hungarian-American theoretical physicist, known colloquially as "the father of the hydrogen bomb," even though he did not care for the title. Teller made numerous contributions to nuclear and molecular physics, spectroscopy , and surface physics...

. The committee reported back to Roosevelt in November that uranium "would provide a possible source of bombs with a destructiveness vastly greater than anything now known."

Briggs proposed that the National Defense Research Committee
National Defense Research Committee
The National Defense Research Committee was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the United States from June 27, 1940 until June 28, 1941...

 (NDRC) spend $167,000 on research into uranium, particularly the uranium-235
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...

 isotope, and the recently discovered plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

. On 28 June 1941, Roosevelt signed Executive Order 8807, which created the Office of Scientific Research and Development
Office of Scientific Research and Development
The Office of Scientific Research and Development was an agency of the United States federal government created to coordinate scientific research for military purposes during World War II. Arrangements were made for its creation during May 1941, and it was created formally by on June 28, 1941...

 (OSRD), with Vannevar Bush
Vannevar Bush
Vannevar Bush was an American engineer and science administrator known for his work on analog computing, his political role in the development of the atomic bomb as a primary organizer of the Manhattan Project, the founding of Raytheon, and the idea of the memex, an adjustable microfilm viewer...

 as its director. The office was empowered to engage in large engineering projects in addition to research. The NDRC Committee on Uranium became the S-1 Uranium Committee of the OSRD; the word "uranium" was soon dropped for security reasons.

In Britain, Otto Frisch and Rudolf Peierls
Rudolf Peierls
Sir Rudolf Ernst Peierls, CBE was a German-born British physicist. Rudolf Peierls had a major role in Britain's nuclear program, but he also had a role in many modern sciences...

 at the University of Birmingham
University of Birmingham
The University of Birmingham is a British Redbrick university located in the city of Birmingham, England. It received its royal charter in 1900 as a successor to Birmingham Medical School and Mason Science College . Birmingham was the first Redbrick university to gain a charter and thus...

 had made a breakthrough investigating the critical mass
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...

 of uranium-235 in June 1939. Their calculations indicated that it was within an order of magnitude
Order of magnitude
An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. In its most common usage, the amount being scaled is 10 and the scale is the exponent being applied to this amount...

 of 10 kilograms (22 lb), which was small enough to be carried by a bomber of the day. Their March 1940 Frisch–Peierls memorandum initiated the British atomic bomb project and its Maud Committee
MAUD Committee
The MAUD Committee was the beginning of the British atomic bomb project, before the United Kingdom joined forces with the United States in the Manhattan Project.-Frisch & Peierls:...

, which unanimously recommended pursuing the development of an atomic bomb. One of its members, the Australian physicist Mark Oliphant
Mark Oliphant
Sir Marcus 'Mark' Laurence Elwin Oliphant, AC, KBE, FRS was an Australian physicist and humanitarian who played a fundamental role in the first experimental demonstration of nuclear fusion and also the development of the atomic bomb.During his retirement, Oliphant was appointed as the Governor of...

, flew to the United States in late August 1941 and discovered that data provided by the Maud Committee had not reached key American physicists. Oliphant then set out to find out why the committee's findings were apparently being ignored. He met with the Uranium Committee, and visited Berkeley, California
Berkeley, California
Berkeley is a city on the east shore of the San Francisco Bay in Northern California, United States. Its neighbors to the south are the cities of Oakland and Emeryville. To the north is the city of Albany and the unincorporated community of Kensington...

, where he spoke persuasively to Ernest O. Lawrence. Lawrence was sufficiently impressed to commence his own research into uranium. He in turn spoke to James B. Conant, Arthur Compton
Arthur Compton
Arthur Holly Compton was an American physicist and Nobel laureate in physics for his discovery of the Compton effect. He served as Chancellor of Washington University in St. Louis from 1945 to 1953.-Early years:...

 and George Pegram. Oliphant's mission was therefore a success; key American physicists were now aware of atomic bomb's potential.

At a meeting between President Roosevelt, Vannevar Bush and Vice President Henry A. Wallace
Henry A. Wallace
Henry Agard Wallace was the 33rd Vice President of the United States , the Secretary of Agriculture , and the Secretary of Commerce . In the 1948 presidential election, Wallace was the nominee of the Progressive Party.-Early life:Henry A...

 on 9 October 1941, the President approved the atomic program. To control it, he created a Top Policy Group consisting of himself—although he never attended a meeting—Wallace, Bush, Conant, Secretary of War
United States Secretary of War
The Secretary of War was a member of the United States President's Cabinet, beginning with George Washington's administration. A similar position, called either "Secretary at War" or "Secretary of War," was appointed to serve the Congress of the Confederation under the Articles of Confederation...

 Henry L. Stimson
Henry L. Stimson
Henry Lewis Stimson was an American statesman, lawyer and Republican Party politician and spokesman on foreign policy. He twice served as Secretary of War 1911–1913 under Republican William Howard Taft and 1940–1945, under Democrat Franklin D. Roosevelt. In the latter role he was a leading hawk...

 and the Chief of Staff of the Army
Chief of Staff of the United States Army
The Chief of Staff of the Army is a statutory office held by a four-star general in the United States Army, and is the most senior uniformed officer assigned to serve in the Department of the Army, and as such is the principal military advisor and a deputy to the Secretary of the Army; and is in...

, General
General (United States)
In the United States Army, United States Air Force, and United States Marine Corps, general is a four-star general officer rank, with the pay grade of O-10. General ranks above lieutenant general and below General of the Army or General of the Air Force; the Marine Corps does not have an...

 George Marshall
George Marshall
George Catlett Marshall was an American military leader, Chief of Staff of the Army, Secretary of State, and the third Secretary of Defense...

. Roosevelt chose the Army to run the project rather than the Navy, as the Army had the most experience with management of large-scale construction projects. He also agreed to coordinate the effort with that of the British, and on 11 October he sent a message to Prime Minister Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...

, suggesting that they correspond on atomic matters.

Proposals



The S-1 Committee held its first meeting on 18 December 1941 "pervaded by an atmosphere of enthusiasm and urgency" in the wake of the attack on Pearl Harbor
Attack on Pearl Harbor
The attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...

 and the subsequent declaration of war by the United States
Declaration of war by the United States
A declaration of war is a formal declaration issued by a national government indicating that a state of war exists between that nation and another. For the United States, Article One, Section Eight of the Constitution says "Congress shall have power to ... declare War"...

 on Japan and Germany. Work was proceeding on three different techniques for isotope separation
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...

 to separate uranium-235 from uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...

. Lawrence and his team at the University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...

, investigated electromagnetic separation, while Eger Murphree and Jesse Wakefield Beams's team looked into gaseous diffusion
Gaseous diffusion
Gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride through semi-permeable membranes. This produces a slight separation between the molecules containing uranium-235 and uranium-238 . By use of a large cascade of many stages, high separations...

 at Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...

, and Philip Abelson
Philip Abelson
Philip Hauge Abelson was an American physicist, a scientific editor, and a science writer.-Life:Abelson was born in 1913 in Tacoma, Washington. He attended Washington State University where he received degrees in chemistry and physics, and the University of California, Berkeley , where he earned...

 directed research into thermal diffusion
Thermophoresis
Thermophoresis, thermodiffusion, or Soret effect , is a phenomenon observed when a mixture of two or more types of motile particles are subjected to the force of a temperature gradient and the different types of particles respond to it differently. The term "Soret effect" normally means...

 at the Carnegie Institution of Washington and later the Naval Research Laboratory. Murphree was also the head of an unsuccessful separation project using centrifuges.

Meanwhile, there were two lines of research into nuclear reactor technology, with Harold Urey
Harold Urey
Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

 continuing research into heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

 at Columbia, while Arthur Compton brought the scientists working under his supervision at Columbia University and Princeton University
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....

 to the University of Chicago
University of Chicago
The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...

, where he organized the Metallurgical Laboratory
Metallurgical Laboratory
The Metallurgical Laboratory or "Met Lab" at the University of Chicago was part of the World War II–era Manhattan Project, created by the United States to develop an atomic bomb...

 in early 1942 to study plutonium and reactors using graphite
Nuclear Graphite
Nuclear graphite is any grade of graphite, usually electro-graphite, specifically manufactured for use as a moderator or reflector within nuclear reactors...

 as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

. Briggs, Compton, Lawrence, Murphree and Urey met on 23 May 1942 to finalize the S-1 Committee recommendations, which called for all five technologies to be pursued. This was approved by Bush, Conant and Brigadier General
Brigadier general (United States)
A brigadier general in the United States Army, Air Force, and Marine Corps, is a one-star general officer, with the pay grade of O-7. Brigadier general ranks above a colonel and below major general. Brigadier general is equivalent to the rank of rear admiral in the other uniformed...

 Wilhelm D. Styer
Wilhelm D. Styer
Wilhelm Delp Styer was a Lieutenant General in the United States Army.-Biography:Styer was born on July 22, 1893, in Salt Lake City, Utah. He was the son of Brigadier General Henry D. Styer , who led U.S...

, the chief of staff of Major General
Major general (United States)
In the United States Army, United States Marine Corps, and United States Air Force, major general is a two-star general-officer rank, with the pay grade of O-8. Major general ranks above brigadier general and below lieutenant general...

 Brehon B. Somervell
Brehon B. Somervell
Brehon Burke Somervell was a General in the United States Army and Commanding General of the Army Service Forces in World War II. As such he was responsible for the U.S. Army's logistics...

's Services of Supply
Services of Supply
The Services Of Supply or "SOS" branch of the Army of the USA was created on 28 February 1942 by Executive Order Number 9082 "Reorganizing the Army and the War Department" and War Department Circular No. 59, dated 2 March 1942. Services of Supply became one of the three autonomous components of the...

, who had been designated the Army's representative on nuclear matters. Bush and Conant then took the recommendation to the Top Policy Group with a budget proposal for $54 million for construction by the United States Army Corps of Engineers
United States Army Corps of Engineers
The United States Army Corps of Engineers is a federal agency and a major Army command made up of some 38,000 civilian and military personnel, making it the world's largest public engineering, design and construction management agency...

, $31 million for research and development by OSRD and $5 million for contingencies in fiscal year 1943. The Top Policy Group in turn sent it to the President on 17 June 1942 and he approved it by writing "OK FDR" on the document.

Bomb design concepts



Compton asked the theoretical physicist J. Robert Oppenheimer of the University of California, Berkeley, to take over research into fast neutron calculations—the key to calculations of critical mass and weapon detonation—from Gregory Breit
Gregory Breit
Gregory Breit was a Russian-born American physicist and professor at universities in New York, Wisconsin, Yale, and Buffalo...

, who had quit on 18 May 1942 because of concerns over lax operational security. John H. Manley, a physicist at the Metallurgical Laboratory, was assigned to assist Oppenheimer by contacting and coordinating experimental physics groups scattered across the country. Oppenheimer and Robert Serber
Robert Serber
Robert Serber was an American physicist who participated in the Manhattan Project. He was born in Philadelphia, Pennsylvania; he was the eldest son of David Serber and Rose Frankel. He married Charlotte Leof in 1933. Rose Serber died in 1922; David married Charlotte's cousin Frances Leof in...

 of the University of Illinois
University of Illinois at Urbana-Champaign
The University of Illinois at Urbana–Champaign is a large public research-intensive university in the state of Illinois, United States. It is the flagship campus of the University of Illinois system...

 examined the problems of neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

 diffusion—how neutrons moved in a nuclear chain reaction
Nuclear chain reaction
A nuclear chain reaction occurs when one nuclear reaction causes an average of one or more nuclear reactions, thus leading to a self-propagating number of these reactions. The specific nuclear reaction may be the fission of heavy isotopes or the fusion of light isotopes...

—and hydrodynamics—how the explosion produced by a chain reaction might behave. To review this work and the general theory of fission reactions, Oppenheimer convened meetings at the University of Chicago in June and at the University of California, Berkeley, in July 1942 with theoretical physicists Hans Bethe
Hans Bethe
Hans Albrecht Bethe was a German-American nuclear physicist, and Nobel laureate in physics for his work on the theory of stellar nucleosynthesis. A versatile theoretical physicist, Bethe also made important contributions to quantum electrodynamics, nuclear physics, solid-state physics and...

, John Van Vleck, Edward Teller
Edward Teller
Edward Teller was a Hungarian-American theoretical physicist, known colloquially as "the father of the hydrogen bomb," even though he did not care for the title. Teller made numerous contributions to nuclear and molecular physics, spectroscopy , and surface physics...

, Emil Konopinski
Emil Konopinski
Emil John Konopinski was an American nuclear scientist of Polish origin. His parents were Joseph and Sophia Sniegowska....

, Robert Serber, Stan Frankel
Stan Frankel
Stanley Phillips "Stan" Frankel was an American computer scientist. He was born in Los Angeles, attended graduate school at the University of Rochester, received his PhD in physics from the University of California, Berkeley, and began his career as a post-doc student under J. Robert Oppenheimer...

, and Eldred C. Nelson, the latter three former students of Oppenheimer, and experimental physicists Felix Bloch
Felix Bloch
Felix Bloch was a Swiss physicist, working mainly in the U.S.-Life and work:Bloch was born in Zürich, Switzerland to Jewish parents Gustav and Agnes Bloch. He was educated there and at the Eidgenössische Technische Hochschule, also in Zürich. Initially studying engineering he soon changed to physics...

, Emilio Segrè, John Manley and Edwin McMillan
Edwin McMillan
Edwin Mattison McMillan was an American physicist and Nobel laureate credited with being the first ever to produce a transuranium element. He shared the Nobel Prize in Chemistry with Glenn Seaborg in 1951....

. They tentatively confirmed that a fission bomb was theoretically possible.

There were still many unknown factors. The properties of pure uranium-235 were relatively unknown, as were those of plutonium, an element that had only been discovered in February 1941 by Glenn Seaborg and his team. The scientists at the Berkeley conference envisioned creating plutonium in nuclear reactors where uranium-238 atoms absorbed neutrons that had been emitted from fissioning uranium-235 atoms. At this point no reactor had been built, and only tiny quantities of plutonium were available from cyclotron
Cyclotron
In technology, a cyclotron is a type of particle accelerator. In physics, the cyclotron frequency or gyrofrequency is the frequency of a charged particle moving perpendicularly to the direction of a uniform magnetic field, i.e. a magnetic field of constant magnitude and direction...

s. Even by December 1943, only two milligrams had been produced. There were many ways of arranging the fissile material into a critical mass. The simplest was shooting a "cylindrical plug" into a sphere of "active material" with a "tamper"—dense material that would focus neutrons inward and keep the reacting mass together to increase its efficiency. They also explored designs involving spheroid
Spheroid
A spheroid, or ellipsoid of revolution is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters....

s, a primitive form of "implosion" suggested by Richard C. Tolman
Richard C. Tolman
Richard Chace Tolman was an American mathematical physicist and physical chemist who was an authority on statistical mechanics. He also made important contributions to theoretical cosmology in the years soon after Einstein's discovery of general relativity...

, and the possibility of autocatalytic methods
Autocatalysis
A single chemical reaction is said to have undergone autocatalysis, or be autocatalytic, if the reaction product itself is the catalyst for that reaction....

, which would increase the efficiency of the bomb as it exploded.

Considering the idea of the fission bomb theoretically settled—at least until more experimental data was available—the Berkeley conference then turned in a different direction. Edward Teller pushed for discussion of a more powerful bomb: the "super", now usually referred to as a "hydrogen bomb", which would use the explosive force of a detonating fission bomb to ignite a nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...

 reaction in deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

 and tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

. Teller proposed scheme after scheme, but Bethe refused each one. The fusion idea was put aside to concentrate on producing fission bombs. Teller also raised the speculative possibility that an atomic bomb might "ignite" the atmosphere because of a hypothetical fusion reaction of nitrogen nuclei. Bethe calculated that it could not happen, and a report co-authored by Teller showed that "no self-propagating chain of nuclear reactions is likely to be started." In Serber's account, Oppenheimer mentioned it to Arthur Compton, who "didn't have enough sense to shut up about it. It somehow got into a document that went to Washington" and was "never laid to rest".

Manhattan District


The Chief of Engineers
Chief of Engineers
The Chief of Engineers commands the US Army Corps of Engineers. As a staff officer at The Pentagon, the Chief advises the Army on engineering matters and serves as the Army's topographer and the proponent for real estate and other related engineering programs....

, Major General Eugene Reybold
Eugene Reybold
Eugene Reybold was distinguished as the World War II Chief of Engineers who directed the largest United States Army Corps of Engineers in the nation's history....

, selected Colonel
Colonel (United States)
In the United States Army, Air Force, and Marine Corps, colonel is a senior field grade military officer rank just above the rank of lieutenant colonel and just below the rank of brigadier general...

 James C. Marshall to head the Army's part of the project in June 1942. Marshall created a liaison office in Washington, D.C., but established his temporary headquarters on the 18th floor of 270 Broadway
Tower 270
Tower 270 is a 28-story mixed use building in Downtown Manhattan that was the headquarters of the Manhattan Project that developed the atomic bomb during World War II.During World War II it was a federal office building...

 in New York, where he could draw on administrative support from the Corps of Engineers' North Atlantic Division
North Atlantic Division
The North Atlantic Division of the U.S. Army Corps of Engineers is one of nine division offices within the Corps. Made up of roughly 3,900 employees in six districts and a Division headquarters, the North Atlantic Division is a major subordinate command and serves to integrate the capabilities of...

. It was close to the Manhattan office of Stone & Webster
Stone & Webster
Stone & Webster is an American engineering services company based in Stoughton, Massachusetts. Stone & Webster was founded as an electrical testing lab and consulting firm by electrical engineers Charles Stone and Edwin Webster in 1889. It was acquired by The Shaw Group in 2000. The company...

, the principal project contractor, and to Columbia University. He had permission to draw on his former command, the Syracuse District, for staff, and he started with Lieutenant Colonel
Lieutenant Colonel (United States)
In the United States Army, United States Air Force, and United States Marine Corps, a lieutenant colonel is a field grade military officer rank just above the rank of major and just below the rank of colonel. It is equivalent to the naval rank of commander in the other uniformed services.The pay...

 Kenneth Nichols
Kenneth Nichols
Kenneth David "Nick" Nichols was a United States Army officer and an engineer. He worked on the Manhattan Project which developed the Atomic Bomb during World War II as Deputy District Engineer and then District Engineer of the Manhattan Engineer District...

, who became his deputy.
Because most of his task involved construction, Marshall worked in cooperation with the head of the Corps of Engineers Construction Division, Major General Thomas M. Robbins, and his deputy, Colonel Leslie Groves
Leslie Groves
Lieutenant General Leslie Richard Groves, Jr. was a United States Army Corps of Engineers officer who oversaw the construction of the Pentagon and directed the Manhattan Project that developed the atomic bomb during World War II. As the son of a United States Army chaplain, Groves lived at a...

. Reybold, Somervell and Styer decided to call the project "Development of Substitute Materials", but Groves felt that this would draw attention. Since engineer districts normally carried the name of the city where they were located, Marshall and Groves agreed to name the Army's component of the project the Manhattan District. This became official on 13 August, when Reybold issued the order creating the new district. Informally, it was known as the Manhattan Engineer District, or MED. Unlike other districts, it had no geographic boundaries, and Marshall had the authority of a division engineer. Development of Substitute Materials remained as the official codename of the project as a whole, but was supplanted over time by "Manhattan".

Marshall later conceded that "I had never never heard of atomic fission but I did know that you could not build much of a plant, much less four of them for $90 million." A single TNT plant that Nichols had recently built in Pennsylvania had cost $128 million. Nor were they impressed with estimates to the nearest order of magnitude, which Groves compared with telling a caterer to prepare for between ten and a thousand guests. A survey team from Stone & Webster had already scouted a site for the production plants. The War Production Board
War Production Board
The War Production Board was established as a government agency on January 16, 1942 by executive order of Franklin D. Roosevelt.The purpose of the board was to regulate the production and allocation of materials and fuel during World War II in the United States...

 recommended sites around Knoxville, Tennessee
Knoxville, Tennessee
Founded in 1786, Knoxville is the third-largest city in the U.S. state of Tennessee, U.S.A., behind Memphis and Nashville, and is the county seat of Knox County. It is the largest city in East Tennessee, and the second-largest city in the Appalachia region...

, an isolated area where the Tennessee Valley Authority
Tennessee Valley Authority
The Tennessee Valley Authority is a federally owned corporation in the United States created by congressional charter in May 1933 to provide navigation, flood control, electricity generation, fertilizer manufacturing, and economic development in the Tennessee Valley, a region particularly affected...

 could supply ample electric power and the rivers could provide cooling water for the reactors. After examining several sites, the survey team selected one near Elza, Tennessee
Elza, Tennessee
Elza was a community in Anderson County, Tennessee, that existed before 1942, when the area was acquired for the Manhattan Project. Its site is now part of the city of Oak Ridge, Tennessee.Elza formed around a flagstop on the Louisville and Nashville Railroad...

. Conant advised that it be acquired at once and Styer agreed but Marshall temporized, awaiting the results of Conant's reactor experiments before taking action. Of the prospective processes, only Lawrence's electromagnetic separation appeared sufficiently advanced for construction to commence.

Marshall and Nichols began assembling the resources they would need. The first step was to obtain a high priority rating for the project. The top ratings were AA-1 through AA-4 in descending order, although there was also a special AAA rating reserved for emergencies. Ratings AA-1 and AA-2 were for essential weapons and equipment, so Colonel Lucius D. Clay
Lucius D. Clay
General Lucius Dubignon Clay was an American officer and military governor of the United States Army known for his administration of Germany immediately after World War II. Clay was deputy to General Dwight D. Eisenhower, 1945; deputy military governor, Germany 1946; commander in chief, U.S....

, the deputy chief of staff at Services and Supply for requirements and resources, felt that the highest rating he could assign was AA-3, although he was willing to provide a AAA rating on request for critical materials if the need arose. Nichols and Marshall were disappointed; AA-3 was the same priority as Nichols' TNT plant in Pennsylvania.

Military Policy Committee



Bush became dissatisfied with Colonel Marshall's failure to get the project moving forward expeditiously, specifically the failure to acquire the Tennessee site, the low priority allocated to the project by the Army and the location of his headquarters in New York City. Bush felt that more aggressive leadership was required, and spoke to Harvey Bundy and Generals Marshall, Somervell and Styer about his concerns. He wanted the project placed under a senior policy committee, with a prestigious officer, preferably Styer, as overall director.

Somervell and Styer selected Groves for the post, informing him on 17 September of this decision, and that General Marshall ordered that he be promoted to brigadier general, as it was felt that the title "general" would hold more sway with the academic scientists working on the Manhattan Project. Groves' orders placed him directly under Somervell rather than Reybold, with Colonel Marshall now answerable to Groves. Groves established his headquarters in Washington, D.C., on the fifth floor of the New War Department Building, where Colonel Marshall had his liaison office. He assumed command of the Manhattan Project on 23 September. Later that day, he attended a meeting called by Stimson, which established a Military Policy Committee, responsible to the Top Policy Group, consisting of Bush (with Conant as an alternate), Styer and Rear Admiral
Rear admiral (United States)
Rear admiral is a naval commissioned officer rank above that of a commodore and captain, and below that of a vice admiral. The uniformed services of the United States are unique in having two grades of rear admirals.- Rear admiral :...

 William R. Purnell. Tolman and Conant were later appointed as Groves' scientific advisers.

On 19 September Groves went to Donald Nelson
Donald M. Nelson
Donald Marr Nelson was an American business executive and public servant, serving as the executive vice president of Sears Roebuck before accepting the position of director of priorities of the United States Office of Production Management . In 1942 Nelson became chairman of the War Production...

, the chairman of the War Production Board
War Production Board
The War Production Board was established as a government agency on January 16, 1942 by executive order of Franklin D. Roosevelt.The purpose of the board was to regulate the production and allocation of materials and fuel during World War II in the United States...

, and asked for broad authority to issue a AAA rating whenever it was required. Nelson initially balked but quickly caved in when Groves threatened to go to the President. Groves promised not to use the AAA rating unless it was necessary. It soon transpired that for the routine requirements of the project the AAA rating was too high but the AA-3 rating was too low. After a long campaign, Groves finally received AA-1 authority on 1 July 1944.

One of Groves' early problems was to find a director for Project Y, the group that would design and build the bomb. The obvious choice was one of the three laboratory heads, Urey, Lawrence or Compton, but they could not be spared. Compton recommended Oppenheimer, who was already intimately familiar with the bomb design concepts. However, Oppenheimer had little administrative experience, and, unlike Urey, Lawrence or Compton, had not won a Nobel Prize, which many scientists felt that the head of such an important laboratory should have. There were also concerns about Oppenheimer's security status, as many of his associates were communists, including his brother, Frank Oppenheimer
Frank Oppenheimer
Frank Friedman Oppenheimer was an American physicist who worked on the Manhattan Project, was a target of McCarthyism, and was later the founder of the Exploratorium in San Francisco. He was the younger brother of J...

; his wife, Kitty; and his girlfriend, Jean Tatlock
Jean Tatlock
Jean Frances Tatlock M.D. , was an American psychiatrist, physician, and a member of the Communist Party. She is most noted for her romantic relationship with Manhattan Project scientific leader J. Robert Oppenheimer....

. A long conversation on a train in October 1942 convinced Groves and Nichols that Oppenheimer thoroughly understood the issues involved in setting up a laboratory in a remote area and should be appointed as its director. Groves personally waived the security requirements and issued Oppenheimer a clearance on 20 July 1943.

Collaboration with the United Kingdom


The British and Americans exchanged nuclear information but did not initially pool their efforts. Britain rebuffed attempts by Bush and Conant in 1941 to strengthen cooperation with its own project, codenamed Tube Alloys
Tube Alloys
Tube Alloys was the code-name for the British nuclear weapon directorate during World War II, when the development of nuclear weapons was kept at such a high level of secrecy that it had to be referred to by code even in the highest circles of government...

. However, the United Kingdom could not muster the manpower or resources of the United States, and despite its early and promising start, Tube Alloys soon fell behind its American counterpart. On 30 July 1942, Sir John Anderson
John Anderson, 1st Viscount Waverley
John Anderson, 1st Viscount Waverley, GCB, OM, GCSI, GCIE, PC, PC was a British civil servant then politician who served as a minister under Neville Chamberlain and Winston Churchill as Home Secretary, Lord President of the Council and Chancellor of the Exchequer...

, the minister responsible, advised Churchill that: "We must face the fact that ... [our] pioneering work ... is a dwindling asset and that, unless we capitalise it quickly, we shall be outstripped. We now have a real contribution to make to a 'merger.' Soon we shall have little or none." By this time, the British bargaining position had worsened, and their motives were mistrusted by the Americans. Collaboration lessened markedly, and the exchange of information stopped. The British investigated the possibility of an independent nuclear program, but determined that it could not be ready in time to affect the outcome of the war in Europe
European Theatre of World War II
The European Theatre of World War II was a huge area of heavy fighting across Europe from Germany's invasion of Poland on September 1, 1939 until the end of the war with the German unconditional surrender on May 8, 1945...

.

In August 1943 Churchill and Roosevelt negotiated the Quebec Agreement
Quebec Agreement
The Quebec Agreement is an Anglo-Canadian-American document outlining the terms of nuclear nonproliferation between the United Kingdom and the United States, and signed by Winston Churchill and Franklin Delano Roosevelt on August 19, 1943, two years before the end of World War II, in Quebec City,...

, which resulted in a resumption of cooperation. The subsequent Hyde Park Agreement in September 1944 extended this cooperation to the postwar period. The Quebec Agreement established the Combined Policy Committee to coordinate the efforts of the United States, United Kingdom and Canada. Stimson, Bush and Conant served as the American members of the Combined Policy Committee, Field Marshal
Field Marshal
Field Marshal is a military rank. Traditionally, it is the highest military rank in an army.-Etymology:The origin of the rank of field marshal dates to the early Middle Ages, originally meaning the keeper of the king's horses , from the time of the early Frankish kings.-Usage and hierarchical...

 Sir John Dill
John Dill
Field Marshal Sir John Greer Dill, GCB, CMG, DSO was a British commander in World War I and World War II. From May 1940 to December 1941 he was the Chief of the Imperial General Staff, the professional head of the British Army, and subsequently in Washington, as Chief of the British Joint Staff...

 and Colonel J. J. Llewellin
John Jestyn Llewellin, 1st Baron Llewellin
Colonel John Jestyn Llewellin, 1st Baron Llewellin GBE, PC, MC, TD was a British army officer, Conservative Party politician and minister in Winston Churchill's war government.-Background:...

 were the British members, and C. D. Howe
C. D. Howe
Clarence Decatur Howe, PC , generally known as C. D. Howe, was a powerful Canadian Cabinet minister of the Liberal Party. Howe served in the governments of Prime Ministers William Lyon Mackenzie King and Louis St. Laurent continuously from 1935 to 1957...

 was the Canadian member. Llewellin returned to the United Kingdom at the end of 1943 and was replaced on the committee by Sir Ronald Ian Campbell
Ronald Ian Campbell
Sir Ronald Ian Campbell CB, GCMG, PC was a British diplomat.Campbell was the second son of Sir Guy Campbell, 3rd Baronet , by Nina, daughter of Frederick Lehmann. He was educated at Eton and graduated from Magdalen College, Oxford in 1912 with a Bachelor of Arts...

, who in turn was replaced by the British Ambassador to the United States, Lord Halifax, in early 1945. Sir John Dill died in Washington, D.C., in November 1944 and was replaced both as Chief of the British Joint Staff Mission and as a member of the Combined Policy Committee by Field Marshal Sir Henry Maitland Wilson.

When cooperation resumed after the Quebec agreement, the Americans' progress and expenditures amazed the British. The United States had already spent more than $1 billion ($ today), while in 1943 the United Kingdom had spent about £0.5 million. James Chadwick
James Chadwick
Sir James Chadwick CH FRS was an English Nobel laureate in physics awarded for his discovery of the neutron....

 thus pressed for British involvement in the Manhattan Project to the fullest extent and abandon any hopes of a British project during the war. With Churchill's backing, he attempted to ensure that every request from Groves for assistance was honored. The British Mission that arrived in the United States in December 1943 included Niels Bohr
Niels Bohr
Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...

, Otto Frisch, Klaus Fuchs
Klaus Fuchs
Klaus Emil Julius Fuchs was a German theoretical physicist and atomic spy who in 1950 was convicted of supplying information from the American, British and Canadian atomic bomb research to the USSR during and shortly after World War II...

, Rudolf Peierls and Ernest Titterton
Ernest William Titterton
Sir Ernest William Titterton Ph. D. was a nuclear physicist and professor.-Early years:...

. More scientists arrived in early 1944. While those assigned to gasseous diffusion left by the fall of 1944, the 35 working with Lawrence at Berkeley were assigned to existing laboratory groups and stayed until the end of the war. The 19 sent to Los Alamos also joined existing groups, primarily related to implosion and bomb assembly, but not the plutonium-related ones. Part of the Quebec Agreement specified that nuclear weapons would not be used against another country without mutual consent. In June 1945 Wilson agreed that the use of nuclear weapons against Japan would be recorded as a decision of the Combined Policy Committee.

The Combined Policy Committee created the Combined Development Trust in June 1944, with Groves as its chairman, to procure uranium and thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....

 ores on international markets. In 1944, the Combined Development Trust purchased 3440000 pounds (1,560,357.8 kg) of uranium oxide ore from companies operating mines in the Belgian Congo. In order to avoid briefing US Secretary of the Treasury Henry Morgenthau Jr. on the project, a special account not subject to the usual auditing and controls was used to hold Trust monies. Between 1944 and the time he resigned from the Trust in 1947, Groves deposited a total of $37.5 million into the Trust's account.

Groves appreciated the early British atomic research and the British scientists' contributions to the Manhattan Project, but stated that the United States would have succeeded without them. Whether or not he was correct, the British wartime participation was crucial to the success of the United Kingdom's independent nuclear weapons program
Nuclear weapons and the United Kingdom
The United Kingdom was the third country to test an independently developed nuclear weapon, in October 1952. It is one of the five "Nuclear Weapons States" under the Nuclear Non-Proliferation Treaty, which the UK ratified in 1968...

 after the war when the McMahon Act of 1946 temporarily ended American nuclear cooperation.

Project sites



Image:Manhattan Project US Canada Map 2.svg|thumb|700px|center|A selection of US and Canadian sites important to the Manhattan Project. Click on the location for more information.|alt=Map of the United States and southern Canada with major project sites marked
circle 50 280 20 Berkeley, California
Lawrence Berkeley National Laboratory
The Lawrence Berkeley National Laboratory , is a U.S. Department of Energy national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus...


circle 140 400 20 Inyokern, California
Naval Air Weapons Station China Lake
- About : is part of under Commander, Navy Installation Command and is located in the Western Mojave Desert region of California, approximately north of Los Angeles. Occupying three counties – Kern, San Bernardino and Inyo – the installation’s closest neighbors are the cities of Ridgecrest,...


circle 170 100 20 Richland, Washington
Hanford Site
The Hanford Site is a mostly decommissioned nuclear production complex on the Columbia River in the U.S. state of Washington, operated by the United States federal government. The site has been known by many names, including Hanford Works, Hanford Engineer Works or HEW, Hanford Nuclear Reservation...


circle 220 20 20 Trail, British Columbia
Trail, British Columbia
Trail is a city in the West Kootenay region of the Interior of British Columbia, Canada.-Geography:Trail has an area of . The city is located on both banks of the Columbia River, approximately 10 km north of the United States border. This section of the Columbia River valley is located between the...


circle 230 270 20 Wendover, Utah
Wendover Air Force Base
Wendover Air Force Base is a former United States Air Force base in Utah now known as Wendover Airport. During World War II it was a training base for B-17 and B-24 bomber crews. It was the training site of the 509th Composite Group, the B-29 unit which dropped the Hiroshima and Nagasaki atomic bombs...


circle 290 360 20 Monticello, Utah
Monticello, Utah
Monticello is a city located in San Juan County, Utah, and is the county seat. It is the second most populous city in San Juan County, with a population of 1,958 at the 2000 census. The Monticello area was settled in July 1887 by pioneers from The Church of Jesus Christ of Latter-day Saints...


circle 320 360 20 Uravan, Colorado
Uravan, Colorado
Uravan is an abandoned uranium mining town in western Montrose County, Colorado, United States, that is now a Superfund site. The town was a company town established by U. S. Vanadium Corporation in 1936 to extract the rich vanadium ore in the region...


circle 340 440 20 Los Alamos, New Mexico
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...


circle 340 500 20 Alamogordo, New Mexico
Trinity test
Trinity was the code name of the first test of a nuclear weapon. This test was conducted by the United States Army on July 16, 1945, in the Jornada del Muerto desert about 35 miles southeast of Socorro, New Mexico, at the new White Sands Proving Ground, which incorporated the Alamogordo Bombing...


circle 610 290 20 Ames, Iowa
Ames Laboratory
Ames Laboratory is a United States Department of Energy national laboratory located in Ames, Iowa. The Laboratory conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup...


circle 660 400 20 St Louis, Missouri
circle 710 310 20 Chicago, Illinois
Argonne National Laboratory
Argonne National Laboratory is the first science and engineering research national laboratory in the United States, receiving this designation on July 1, 1946. It is the largest national laboratory by size and scope in the Midwest...


circle 730 370 20 Dana, Indiana
Newport Chemical Depot
The Newport Chemical Depot, previously known as the Wabash River Ordinance Works and the Newport Army Ammunition Plant, was a bulk chemical storage and destruction facility in west central Indiana, thirty miles north of Terre Haute operated by the United States Army...


circle 800 350 20 Dayton, Ohio
Dayton Project
The Dayton Project was one of several sites involved in the Manhattan Project to build the first atomic bombs. Charles Allen Thomas, an executive of the Monsanto Company corporation, was assigned to develop the neutron generating devices that triggered the nuclear detonation of the atomic bombs...


circle 760 540 20 Sylacauga, Alabama
Alabama Army Ammunition Plant
The Alabama Army Ammunition Plant , was a United States munitions plant built and operated during World War II. The facility is located a four miles north of Childersburg, Alabama in Talladega County, Alabama.-History:...


circle 890 390 20 Morgantown, West Virginia
Morgantown, West Virginia
Morgantown is a city in Monongalia County, West Virginia. It is the county seat of Monongalia County. Placed along the banks of the Monongahela River, Morgantown is the largest city in North-Central West Virginia, and the base of the Morgantown metropolitan area...


circle 800 460 20 Oak Ridge, Tennessee
Oak Ridge, Tennessee
Oak Ridge is a city in Anderson and Roane counties in the eastern part of the U.S. state of Tennessee, about west of Knoxville. Oak Ridge's population was 27,387 at the 2000 census...


circle 910 160 20 Chalk River Laboratories
Chalk River Laboratories
The Chalk River Laboratories is a Canadian nuclear research facility located near Chalk River, about north-west of Ottawa in the province of Ontario.CRL is a site of major research and development to support and advance nuclear technology, in particular CANDU reactor...


circle 920 260 20 Rochester, New York
Rochester, New York
Rochester is a city in Monroe County, New York, south of Lake Ontario in the United States. Known as The World's Image Centre, it was also once known as The Flour City, and more recently as The Flower City...


circle 950 360 20 Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....


desc none

Oak Ridge



The day after he took over the project, Groves took a train to Tennessee with Colonel Marshall to inspect the proposed site there, and Groves was impressed. On 29 September, United States Under Secretary of War
United States Under Secretary of War
The Under Secretary of War was a position created by an act of 16 December 1940 . At the same time, section 5a of the National Defense Act was amended to allow the United States Secretary of War to assign his responsibilities for procurement to any of his subordinates...

 Robert P. Patterson
Robert P. Patterson
Robert Porter Patterson was the United States Under Secretary of War under President Franklin Roosevelt and the United States Secretary of War under President Harry S. Truman from September 27, 1945 to July 18, 1947....

 authorized the Corps of Engineers to compulsorily acquire
Eminent domain
Eminent domain , compulsory purchase , resumption/compulsory acquisition , or expropriation is an action of the state to seize a citizen's private property, expropriate property, or seize a citizen's rights in property with due monetary compensation, but without the owner's consent...

 56000 acres (22,662.4 ha) of land at a cost of $3.5 million. An additional 3000 acres (1,214.1 ha) was subsequently acquired. About 1,000 families were affected by the condemnation order, which came into effect on 7 October. Protests, legal appeals, and a 1943 congressional inquiry were to no avail. By mid-November US Marshals were tacking notices to vacate on farmhouse doors, and construction contractors were moving in. Some families were given two weeks' notice to vacate farms that had been their homes for generations; others had settled there after being evicted to make way for the Great Smoky Mountains National Park
Great Smoky Mountains National Park
Great Smoky Mountains National Park is a United States National Park and UNESCO World Heritage Site that straddles the ridgeline of the Great Smoky Mountains, part of the Blue Ridge Mountains, which are a division of the larger Appalachian Mountain chain. The border between Tennessee and North...

 in the 1920s or the Norris Dam
Norris Dam
Norris Dam is a hydroelectric and flood control structure located on the Clinch River in Anderson County and Campbell County, Tennessee, USA. Its construction in the mid-1930s was the first major project for the Tennessee Valley Authority, which had been created in 1933 to bring economic...

 in the 1930s. The ultimate cost of land acquisition in the area, which was not completed until March 1945, was only about $2.6 million, which worked out to around $47 an acre. When presented with Public Proclamation Number Two, which declared Oak Ridge a total exclusion area that no one could enter without military permission, the Governor of Tennessee, Prentice Cooper
Prentice Cooper
William Prentice Cooper was an American politician and Governor of Tennessee from 1939 to 1945.-Life and career:A native of Bedford County, Tennessee, he attended Vanderbilt University and then Harvard University...

, angrily tore it up.

Initially known as the Kingston Demolition Range, the site was officially renamed the Clinton Engineer Works
Clinton Engineer Works
The Clinton Engineer Works was the Army name for the Manhattan Project production facility in World War II for enriched uranium used in the Little Boy atomic bomb dropped on Hiroshima in 1945, and would have produced enough enriched uranium for a second Little Boy gun-type bomb by December 1945...

 (CEW) in early 1943. To enable Stone and Webster to concentrate on the production facilities, a residential community for 13,000 was designed and built by the architectural and engineering firm Skidmore, Owings and Merrill
Skidmore, Owings and Merrill
Skidmore, Owings and Merrill LLP is an American architectural and engineering firm that was formed in Chicago in 1936 by Louis Skidmore and Nathaniel Owings; in 1939 they were joined by John O. Merrill. They opened their first branch in New York City, New York in 1937. SOM is one of the largest...

. The community was located on the slopes of Black Oak Ridge, from which the new town of Oak Ridge
Oak Ridge, Tennessee
Oak Ridge is a city in Anderson and Roane counties in the eastern part of the U.S. state of Tennessee, about west of Knoxville. Oak Ridge's population was 27,387 at the 2000 census...

 got its name. The Army presence at Oak Ridge increased in August 1943 when Nichols replaced Marshall as head of the Manhattan Engineer District. One of his first tasks was to move the district headquarters to Oak Ridge although the name of the district did not change. In September 1943 the administration of community facilities was outsourced to Turner Construction Company through a subsidiary known as the Roane-Anderson Company after Anderson
Anderson County, Tennessee
Anderson County is a U.S. county located in the U.S. state of Tennessee. As of the 2010 census, its population is 75,129. Its county seat is Clinton.It is included in the Knoxville, Tennessee, Metropolitan Statistical Area.-Geography:...

 and Roane counties, in which Oak Ridge was located. The population of Oak Ridge soon expanded well beyond the initial plans, and peaked at 75,000 in May 1945, by which time 82,000 people were employed at the Clinton Engineer Works, and 10,000 by Roane-Anderson.

Los Alamos



The idea of locating Project Y at Oak Ridge was considered, but in the end it was decided that it should be in a remote location. On Oppenheimer's recommendation, the search for a suitable site was narrowed to the vicinity of Albuquerque, New Mexico
Albuquerque, New Mexico
Albuquerque is the largest city in the state of New Mexico, United States. It is the county seat of Bernalillo County and is situated in the central part of the state, straddling the Rio Grande. The city population was 545,852 as of the 2010 Census and ranks as the 32nd-largest city in the U.S. As...

, where Oppenheimer owned a ranch. In October 1942, Major John H. Dudley of the Manhattan Project was sent to survey the area, and he recommended a site near Jemez Springs, New Mexico
Jemez Springs, New Mexico
Jemez Springs is a village in Sandoval County, New Mexico, United States. The population was 375 at the 2000 census. Named for the nearby Pueblo of Jemez, the village is the site of Jemez State Monument and the headquarters of the Jemez Ranger District...

. On 16 November, Oppenheimer, Groves, Dudley and others toured the site. Oppenheimer feared that the high cliffs surrounding the site would make his people feel claustrophobic, while the engineers were concerned with the possibility of flooding. The party then moved on to the vicinity of the Los Alamos Ranch School
Los Alamos Ranch School
Los Alamos Ranch School was a private boarding school for boys in Los Alamos County, New Mexico, near Otowi, in what would eventually become Los Alamos, New Mexico...

. Oppenheimer was impressed and expressed a strong preference for the site, citing its natural beauty and views of the Sangre de Cristo Mountains
Sangre de Cristo Mountains
The Sangre de Cristo Mountains are the southernmost subrange of the Rocky Mountains. They are located in southern Colorado and northern New Mexico in the United States...

, which, it was hoped, would inspire those who would work on the project. The engineers were concerned about the poor access road, and whether the water supply would be adequate, but otherwise felt that it was ideal.


Patterson approved the acquisition of the site on 25 November 1942, authorizing $440,000 for the purchase of the site of 54000 acres (21,853 ha), all but 8900 acres (3,601.7 ha) of which were already owned by the Federal Government. Secretary of Agriculture Claude R. Wickard
Claude R. Wickard
Claude Raymond Wickard served as Secretary of Agriculture under President Franklin D. Roosevelt from 1940 to 1945. Wickard was born on his family farm in Carroll County, Indiana, near Camden...

 granted use of some 45100 acres (18,251.3 ha) of United States Forest Service
United States Forest Service
The United States Forest Service is an agency of the United States Department of Agriculture that administers the nation's 155 national forests and 20 national grasslands, which encompass...

 land to the War Department "for so long as the military necessity continues". The need for land for a new road, and later for a right of way for a 25 miles (40.2 km) power line, eventually brought wartime land purchases to 45737 acres (18,509.1 ha), but only $414,971 was spent. Construction was contracted to the M. M. Sundt Company of Tucson, Arizona
Tucson, Arizona
Tucson is a city in and the county seat of Pima County, Arizona, United States. The city is located 118 miles southeast of Phoenix and 60 miles north of the U.S.-Mexico border. The 2010 United States Census puts the city's population at 520,116 with a metropolitan area population at 1,020,200...

, with Willard C. Kruger and Associates of Santa Fe, New Mexico
Santa Fe, New Mexico
Santa Fe is the capital of the U.S. state of New Mexico. It is the fourth-largest city in the state and is the seat of . Santa Fe had a population of 67,947 in the 2010 census...

, as architect and engineer. Work commenced in December 1942. Groves initially allocated $300,000 for construction, three times Oppenheimer's estimate, with a planned completion date of 15 March 1943. It soon became clear that the scope of Project Y was greater than expected, and by the time Sundt finished in 30 November 1943, over $7 million had been spent.

Because it was secret, Los Alamos was referred to as "Site Y" or "the Hill". Birth certificates of babies born in Los Alamos during the war listed their place of birth as PO Box 1663 in Santa Fe. Initially Los Alamos was to have been a military laboratory with Oppenheimer and other researchers commissioned into the Army. Oppenheimer went so far as to order himself a lieutenant colonel's uniform, but two key physicists, Robert Bacher
Robert Bacher
Robert Fox Bacher was an American nuclear physicist and one of the leaders of the Manhattan Project.-Early life and career:...

 and Isidor Rabi, balked at the idea. Conant, Groves and Oppenheimer then devised a compromise whereby the laboratory was operated by the University of California under contract to the War Department.

Argonne


An Army-OSRD council on 25 June 1942 decided to build a pilot plant
Pilot plant
A pilot plant is a small chemical processing system which is operated to generate information about the behavior of the system for use in design of larger facilities....

 for plutonium production in the Argonne Forest
Waterfall Glen Forest Preserve
Waterfall Glen Forest Preserve is a forest preserve in southern DuPage County. It is known for its waterfall, which actually is a dam, which is in its ravine. It completely surrounds Argonne National Laboratory...

 southwest of Chicago. In July, Nichols arranged for a lease of 1000 acres (404.7 ha) from Cook County, Illinois
Cook County, Illinois
Cook County is a county in the U.S. state of Illinois, with its county seat in Chicago. It is the second most populous county in the United States after Los Angeles County. The county has 5,194,675 residents, which is 40.5 percent of all Illinois residents. Cook County's population is larger than...

, and Captain James F. Grafton was appointed Chicago area engineer. It soon became apparent that the scale of operations was too great for the Argonne, and it was decided to build the plant at Oak Ridge.

Delays in establishing Argonne led Compton to authorize construction of the first nuclear reactor beneath the bleachers of Stagg Field
Stagg Field
Amos Alonzo Stagg Field is the name of two different football fields for the University of Chicago. The earliest Stagg Field is probably best remembered for its role in a landmark scientific achievement by Enrico Fermi during the Manhattan Project. The site of the first nuclear reaction received...

 at the University of Chicago. On 2 December 1942 a team led by Enrico Fermi
Enrico Fermi
Enrico Fermi was an Italian-born, naturalized American physicist particularly known for his work on the development of the first nuclear reactor, Chicago Pile-1, and for his contributions to the development of quantum theory, nuclear and particle physics, and statistical mechanics...

 initiated the first artificial self-sustaining nuclear chain reaction in an experimental reactor known as Chicago Pile-1
Chicago Pile-1
Chicago Pile-1 was the world's first man-made nuclear reactor. CP-1 was built on a rackets court, under the abandoned west stands of the original Alonzo Stagg Field stadium, at the University of Chicago. The first self-sustaining nuclear chain reaction was initiated in CP-1 on December 2, 1942...

. The point at which a reaction becomes self-sustaining became known as "going critical". Compton reported the success to Conant in Washington, D.C., by a coded phone call, saying, "The Italian navigator [Fermi] has just landed in the new world." In January 1943, Grafton's successor, Major Arthur V. Peterson, ordered Chicago Pile-1 dismantled and reassembled at Argonne, as he regarded the operation of a reactor as too hazardous for a densely populated area.

Hanford


By December 1942 there were concerns that even Oak Ridge was too close to a major population center (Knoxville) in the unlikely event of a major nuclear accident. Groves recruited DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...

 in November 1942 to be the prime contractor for the construction of the plutonium production complex. DuPont was offered a standard cost plus fixed fee contract
Cost-plus contract
A cost-plus contract, also termed a Cost Reimbursement Contract, is a contract where a contractor is paid for all of its allowed expenses to a set limit plus additional payment to allow for a profit. Cost-reimbursement contracts contrast with fixed-price contract, in which the contractor is paid a...

, but the President of the company, Walter S. Carpenter, Jr.
Walter S. Carpenter, Jr.
Walter Samuel Carpenter, Jr. was an American corporate executive from Wilmington, Delaware who oversaw the DuPont company's involvement in the Manhattan Project to produce an atomic bomb for use during World War II...

, wanted no profit of any kind, and asked for the proposed contract to be amended to explicitly exclude the company from acquiring any patent rights. This was accepted, but for legal reasons a nominal fee of one dollar was agreed upon. After the war, DuPont asked to be released from the contract early, and had to return 33 cents.


DuPont recommended that the site be located far from the existing uranium production facility at Oak Ridge. In December 1942, Groves dispatched Colonel Franklin Matthias
Franklin Matthias
Franklin T. Matthias was an American nuclear engineer who directed construction of the Hanford nuclear site, a key facility of the Manhattan Project during World War II. As a 34-year-old lieutenant colonel with the Army Corps of Engineers, he was appointed to the Hanford project by General Leslie...

 and DuPont engineers to scout potential sites. Matthias reported that Hanford Site
Hanford Site
The Hanford Site is a mostly decommissioned nuclear production complex on the Columbia River in the U.S. state of Washington, operated by the United States federal government. The site has been known by many names, including Hanford Works, Hanford Engineer Works or HEW, Hanford Nuclear Reservation...

 near Richland, Washington
Richland, Washington
Richland is a city in Benton County in the southeastern part of the U.S. state of Washington, at the confluence of the Yakima and the Columbia Rivers. As of the 2010 census, the city population was 48,058. April 1, 2011 estimates from the Washington State Office of Financial Management put the...

, was "ideal in virtually all respects". It was isolated and near the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...

, which could supply sufficient water to cool the reactors that would produce the plutonium. Groves visited the site in January and established the Hanford Engineer Works (HEW), codenamed "Site W".

Under Secretary Patterson gave his approval on 9 February, allocating $5 million for the acquisition of 40000 acres (16,187.4 ha) of land in the area. The federal government relocated some 1,500 residents of White Bluffs
White Bluffs, Washington
White Bluffs was an agricultural town in Benton County, Washington, United States. It was evacuated in 1943 along with the town of Hanford to make room for the nuclear production facility known as the Hanford Site....

 and Hanford
Hanford, Washington
Hanford was a small agricultural community in Benton County, Washington, United States. It was evacuated in 1943 along with the town of White Bluffs in order to make room for the nuclear production facility known as the Hanford Site...

, and nearby settlements, as well as the Wanapum
Wanapum
The Wanapum tribe of Native Americans formerly lived along the Columbia River from above Priest Rapids down to the mouth of the Snake River in what is now the U.S. state of Washington. About 60 Wanapum still live near the present day site of Priest Rapids Dam...

 and other tribes using the area. A dispute arose with farmers over compensation for crops, which had already been planted before the land was acquired. Where schedules allowed, the Army allowed the crops to be harvested, but this was not always possible. The land acquisition process dragged on and was not completed before the end of the Manhattan Project in December 1946.

The dispute did not delay work. Although progress on the reactor design at Metallurgical Laboratory and DuPont was not sufficiently advanced to accurately predict the scope of the project, a start was made in April 1943 on facilities for an estimated 25,000 workers, half of whom were expected to live on-site. By July 1944, some 1,200 buildings had been erected and nearly 51,000 people were living in the construction camp. As area engineer, Matthias exercised overall control of the site. At its peak, the construction camp was the third most populous town in Washington state. Hanford operated a fleet of over 900 buses, more than the city of Chicago. Like Los Alamos and Oak Ridge, Richland was a gated community with restricted access, but it looked more like a typical wartime American boomtown: the military profile was lower, and physical security elements like high fences, towers and guard dogs were less evident.

Canadian sites


Cominco had produced electrolytic hydrogen at Trail, British Columbia
Trail, British Columbia
Trail is a city in the West Kootenay region of the Interior of British Columbia, Canada.-Geography:Trail has an area of . The city is located on both banks of the Columbia River, approximately 10 km north of the United States border. This section of the Columbia River valley is located between the...

, since 1930. Urey suggested in 1941 that it could produce heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

. To the existing $10 million plant consisting of 3,215 cells consuming 75 MW of hydroelectric power, secondary electrolysis cells were added to increase the deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

 concentration in the water from 2.3% to 99.8%. For this process, Hugh Taylor of Princeton developed a platinum-on-carbon catalyst for the first three stages while Urey developed a nickel-chromia
Chromium(III) oxide
Chromium oxide is the inorganic compound of the formula Cr2O3. It is one of principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite.-Structure and properties:...

 one for the fourth stage tower. The final cost was $2.8 million. The Canadian Government did not officially learn of the project until August 1942. Trail's heavy water production started in January 1944 and continued until 1956. Heavy water from Trail was used for the Argonne reactor, the first reactor using heavy water and natural uranium, which went critical on 15 May 1944.

The Chalk River, Ontario
Chalk River Laboratories
The Chalk River Laboratories is a Canadian nuclear research facility located near Chalk River, about north-west of Ottawa in the province of Ontario.CRL is a site of major research and development to support and advance nuclear technology, in particular CANDU reactor...

, site was established to rehouse the Allied effort at the Montreal Laboratory
Montreal Laboratory
The Montreal Laboratory in Montreal, Quebec, Canada was established by the National Research Council of Canada to undertake nuclear research, and to take over some of the scientists and projects from the Tube Alloys nuclear project in Britain...

 at McGill University
McGill University
Mohammed Fathy is a public research university located in Montreal, Quebec, Canada. The university bears the name of James McGill, a prominent Montreal merchant from Glasgow, Scotland, whose bequest formed the beginning of the university...

 away from an urban area. A new community was built at Deep River, Ontario
Deep River, Ontario
Deep River is a town in Renfrew County, Ontario, Canada. Located along the Ottawa River, it lies about north-west of Ottawa on the Trans-Canada Highway...

, to provide residences and facilities for the team members. The site was chosen for its proximity to the industrial manufacturing area of Ontario and Quebec, and proximity to a rail head adjacent to a large military base, Camp Petawawa. Located on the Ottawa River, it had access to abundant water. The first director of the new laboratory was John Cockroft, later replaced by Bennett Lewis
Bennett Lewis
Wilfrid Bennett Lewis, was a Canadian nuclear scientist and administrator, and was centrally involved in the development of the CANDU reactor....

. A pilot reactor known as ZEEP
ZEEP
The ZEEP reactor was a nuclear reactor built at the Chalk River Laboratories near Chalk River, Ontario, Canada . ZEEP first went critical at 3:45 PM, September 5, 1945...

 (zero-energy experimental pile) became the first Canadian reactor, and the first to be completed outside the United States, when it went critical in September 1945. A larger 10 MW NRX
NRX
NRX was a heavy water moderated, light water cooled, nuclear research reactor at the Canadian Chalk River Laboratories, which came into operation in 1947 at a design power rating of 10 MW , increasing to 42 MW by 1954...

 reactor, which was designed during the war, was completed and went critical in July 1947.

Heavy water sites


Although DuPont's preferred designs for the nuclear reactors were helium cooled and used graphite as a moderator, DuPont still expressed an interest in using heavy water as a backup, in case the graphite reactor design proved infeasible for some reason. For this purpose, it was estimated that 3 LT of heavy water would be required per month. As the plant at Trail, which was then under construction, could produce 0.5 LT per month, additional capacity was required. Groves therefore authorized DuPont to establish heavy water facilities at the Morgantown Ordnance Works, near Morgantown, West Virginia
Morgantown, West Virginia
Morgantown is a city in Monongalia County, West Virginia. It is the county seat of Monongalia County. Placed along the banks of the Monongahela River, Morgantown is the largest city in North-Central West Virginia, and the base of the Morgantown metropolitan area...

; at the Wabash River Ordnance Works
Newport Chemical Depot
The Newport Chemical Depot, previously known as the Wabash River Ordinance Works and the Newport Army Ammunition Plant, was a bulk chemical storage and destruction facility in west central Indiana, thirty miles north of Terre Haute operated by the United States Army...

, near Dana
Dana, Indiana
Dana is a town in Helt Township, Vermillion County, Indiana, United States. The population was 608 at the 2010 census. It is primarily a farming community.Famed World War II war correspondent Ernie Pyle was born on a tenant farm near Dana...

 and Newport, Indiana
Newport, Indiana
Newport is a town in Vermillion Township, Vermillion County, Indiana, United States. The population was 515 at the 2010 census. The town is the county seat of Vermillion County.-Geography:Newport is located at ....

; and at the Alabama Ordnance Works
Alabama Army Ammunition Plant
The Alabama Army Ammunition Plant , was a United States munitions plant built and operated during World War II. The facility is located a four miles north of Childersburg, Alabama in Talladega County, Alabama.-History:...

, near Childersburg
Childersburg, Alabama
Childersburg is a city in Talladega county in the U.S. state of Alabama. At the 2000 census the population was 4,927. It claims a history dating back before 1540, when it was noted as a village of the Coosa Nation visited by the Spanish explorer Hernando de Soto...

 and Sylacauga, Alabama
Sylacauga, Alabama
Sylacauga is a city in Talladega County, Alabama, United States. At the 2000 census the population was 12,616.Nicknames for Sylacauga include: "The Marble City," "Buzzard's Roost" and "Sly Town"....

. Although known as Ordnance Works and paid for under Ordnance Department contracts, they were built and operated by the Army Corps of Engineers. The American plants used a process different from Trail's; heavy water was extracted by distillation, taking advantage of the slightly higher boiling point of heavy water.

Ore


The key raw material for the project was uranium, which was used as fuel for the reactors, as feed that was transformed into plutonium, and, in its enriched form, in the atomic bomb itself. There were four known major deposits of uranium in 1940: in Colorado, in northern Canada, in Joachimstal in Czechoslovakia, and in the Belgian Congo
Belgian Congo
The Belgian Congo was the formal title of present-day Democratic Republic of the Congo between King Leopold II's formal relinquishment of his personal control over the state to Belgium on 15 November 1908, and Congolese independence on 30 June 1960.-Congo Free State, 1884–1908:Until the latter...

. All but Joachimstal were in allied hands. A November 1942 survey determined that sufficient quantities of uranium were available to satisfy the project's requirements. Nichols arranged with the State Department for export controls to be placed on uranium oxide
Uranium oxide
Uranium oxide is an oxide of the element uranium.The metal uranium forms several oxides:* Uranium dioxide or uranium oxide * Uranium trioxide or uranium oxide...

 and negotiated for the purchase of 1200 LT of uranium ore from the Belgian Congo that was being stored in a warehouse on Staten Island
Staten Island
Staten Island is a borough of New York City, New York, United States, located in the southwest part of the city. Staten Island is separated from New Jersey by the Arthur Kill and the Kill Van Kull, and from the rest of New York by New York Bay...

. He negotiated with Eldorado Gold Mines for the purchase of ore from its mine in Port Hope, Ontario, and its shipment in 100-ton lots. The Canadian government subsequently bought up the company's stock until it acquired a controlling interest.

The richest source of ore was the Shinkolobwe
Shinkolobwe
Shinkolobwe is the name of a town and a mine in the Katanga province of the Democratic Republic of the Congo , located near the larger town of Likasi and about 120 miles northwest of Lubumbashi. The former mine was located in the centre of a 400 kilometre long belt of uranified minerals, stretching...

 mine in the Belgian Congo, but it was flooded and closed. Nichols unsuccessfully attempted to negotiate its reopening with Edgar Sengier
Edgar Sengier
Edgar Sengier was the director of the Belgian Union Minière du Haut Katanga during World War II. Sengier is credited with giving the American government access to much of the uranium necessary for the Manhattan Project...

, the director of the company that owned the mine, Union Minière du Haut Katanga
Union Minière du Haut Katanga
The Union Minière du Haut Katanga was a Belgian mining company, once operating in Katanga, in what is now the Democratic Republic of the Congo...

. The matter was then taken up by the Combined Policy Committee. As 30 percent of Union Minière's stock was controlled by British interests, the British took the lead in negotiations. Sir John Anderson
John Anderson, 1st Viscount Waverley
John Anderson, 1st Viscount Waverley, GCB, OM, GCSI, GCIE, PC, PC was a British civil servant then politician who served as a minister under Neville Chamberlain and Winston Churchill as Home Secretary, Lord President of the Council and Chancellor of the Exchequer...

 and Ambassador John Winant hammered out a deal with Sengier and the Belgian government in May 1944 for the mine to be reopened and 1720 LT of ore to be supplied. To avoid dependence on the British and Canadians for ore, Groves also arranged for the purchase of US Vanadium Corporation's stockpile in Uravan, Colorado
Uravan, Colorado
Uravan is an abandoned uranium mining town in western Montrose County, Colorado, United States, that is now a Superfund site. The town was a company town established by U. S. Vanadium Corporation in 1936 to extract the rich vanadium ore in the region...

. Uranium mining in Colorado
Uranium mining in Colorado
Uranium mining in Colorado, United States, goes back to 1872, when pitchblende ore was taken from gold mines near Central City, Colorado. The Colorado uranium industry has seen booms and busts, but continues to this day...

 yielded about 800 LT of ore.

Mallinckrodt Incorporated in St. Louis, Missouri, took the raw ore and dissolved it in nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

 to produce uranyl nitrate
Uranyl nitrate
Uranyl nitrate is a water soluble yellow uranium salt. The yellow-green crystals of uranium nitrate hexahydrate are triboluminescent.Uranyl nitrate can be prepared by reaction of uranium salts with nitric acid...

. Ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...

 was then added in a liquid-liquid extraction
Liquid-liquid extraction
Liquid–liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid phase into another liquid...

 process to separate the impurities from the uranyl nitrate. This was then heated to form uranium trioxide
Uranium trioxide
Uranium trioxide , also called uranyl oxide, uranium oxide, and uranic oxide, is the hexavalent oxide of uranium. The solid may be obtained by heating uranyl nitrate to 400 °C. Its most commonly encountered polymorph, γ-UO3, is a yellow-orange powder.-Production and use:There are three methods...

, which was reduced to highly pure uranium dioxide
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...

. By July 1942, Mallinckrodt was producing a ton of highly pure oxide a day, but turning this into uranium metal initially proved more difficult for contractors Westinghouse
Westinghouse Electric (1886)
Westinghouse Electric was an American manufacturing company. It was founded in 1886 as Westinghouse Electric Company and later renamed Westinghouse Electric Corporation by George Westinghouse. The company purchased CBS in 1995 and became CBS Corporation in 1997...

 and Metal Hydrides. Production was too slow and quality was unacceptably low. A special branch of the Metallurgical Laboratory was established at Iowa State College in Ames, Iowa, under Frank Spedding
Frank Spedding
Frank Harold Spedding was a Canadian chemist who led a group of chemists at Ames Laboratory which developed an efficient process for obtaining high purity uranium from uranium halides. The general technique is known as the Thermite process, or more specifically, the Ames process...

 to investigate alternatives, and its Ames process
Ames process
The Ames process is a process by which pure uranium metal is obtained. It can be achieved by mixing any of the uranium halides with magnesium metal powder or aluminium metal powder.- History :...

 became available in 1943.

Isotope separation


Natural uranium consists of 99.3% uranium-238 and 0.7% uranium-235, but only the latter is fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...

. The chemically identical uranium-235 has to be physically separated from the more plentiful isotope. Various methods were considered for uranium enrichment, most of which was carried out at Oak Ridge.

The most obvious technology, the centrifuge, failed, but electromagnetic separation, gaseous diffusion, and thermal diffusion technologies were all successful and contributed to the project. In February 1943, Groves came up with the idea of using the output of some plants as the input for others.

Centrifuges


The centrifuge process was regarded as the only promising separation method in April 1942. Jesse Beams
Jesse Beams
Jesse Wakefield Beams was an American physicist at the University of Virginia.Beams completed his undergraduate B.A. in physics at Fairmount College in 1921 and his master's degree the next year at the University of Wisconsin–Madison...

 had developed such a process at the University of Virginia
University of Virginia
The University of Virginia is a public research university located in Charlottesville, Virginia, United States, founded by Thomas Jefferson...

 during the 1930s, but had encountered technical difficulties. The process required high rotational speeds, but at certain speeds harmonic vibrations developed that threatened to tear the machinery apart. It was therefore necessary to accelerate quickly through these speeds. In 1941 he began working with uranium hexafluoride
Uranium hexafluoride
Uranium hexafluoride , referred to as "hex" in the nuclear industry, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and nuclear weapons. It forms solid grey crystals at standard temperature and pressure , is highly toxic, reacts violently with water...

, the only known gaseous compound of uranium, and was able to separate uranium-235. At Columbia, Urey had Cohen investigate the process, and he produced a body of mathematical theory making it possible to design a centrifugal separation unit, which Westinghouse undertook to construct.

Scaling this up to a production plant presented a formidable technical challenge. Urey and Cohen estimated that producing a kilogram (2.2 lb) of uranium-235 per day would require up to 50,000 centrifuges with 1 metres (3.3 ft) rotors, or 10,000 centrifuges with 4 metres (13.1 ft) rotors, assuming that 4-meter rotors could be built. The prospect of keeping so many rotors operating continuously at high speed appeared daunting, and when Beams ran his experimental apparatus, he obtained only 60% of the predicted yield, indicating that more centrifuges would be required. Beams, Urey and Cohen then began work on a series of improvements which promised to increase the efficiency of the process. However, frequent failures of motors, shafts and bearings at high speeds delayed work on the pilot plant. In November 1942 the centrifuge process was abandoned by the Military Policy Committee following a recommendation by Conant, Nichols and August C. Klein of Stone & Webster.

Electromagnetic separation


Electromagnetic isotope separation was developed by Lawrence at the University of California Radiation Laboratory. This method employed devices known as calutron
Calutron
A calutron is a mass spectrometer used for separating the isotopes of uranium. It was developed by Ernest O. Lawrence during the Manhattan Project and was similar to the cyclotron invented by Lawrence. Its name is a concatenation of Cal. U.-tron, in tribute to the University of California,...

s, a hybrid of the standard laboratory mass spectrometer and cyclotron. The name was derived from the words "California", "university" and "cyclotron". In the electromagnetic process, a magnetic field deflected charged particles according to mass. The process was neither scientifically elegant nor industrially efficient. Compared with a gaseous diffusion plant or a nuclear reactor, an electromagnetic separation plant would consume more scarce materials, require more manpower to operate, and cost more to build. Nonetheless, the process was approved because it was based on proven technology and therefore represented less risk. Moreover, it could be built in stages, and rapidly reach industrial capacity.


Marshall and Nichols discovered that the electromagnetic isotope separation process would require 5,000 tons of copper, which was in desperately short supply. However, silver could be substituted, in an 11:10 ratio. On 3 August 1942, Nichols met with Under Secretary of the Treasury
United States Deputy Secretary of the Treasury
The Deputy Secretary of the Treasury, in the United States government, advises and assists the Secretary of the Treasury in the supervision and direction of the Department of the Treasury and its activities, and succeeds the Secretary in his absence, sickness, or unavailability...

 Daniel W. Bell
Daniel W. Bell
Daniel W. Bell was an American civil servant and businessman. Born in Kinderhook, Illinois, he was acting director of the Bureau of the Budget from September 1, 1934 until April 14, 1939....

 and asked for the transfer of 6,000 tons of silver bullion from the West Point Depository. "Young man," Bell told him, "you may think of silver in tons but the Treasury will always think of silver in troy ounce
Troy ounce
The troy ounce is a unit of imperial measure. In the present day it is most commonly used to gauge the weight of precious metals. One troy ounce is nowadays defined as exactly 0.0311034768 kg = 31.1034768 g. There are approximately 32.1507466 troy oz in 1 kg...

s!" Eventually, 14,700 tons were used.

The 1000 troy ounces (31.1 kg) silver bars were cast into cylindrical billets and taken to Phelps Dodge
Phelps Dodge
Phelps Dodge Corporation was an American mining company founded in 1834 by Anson Greene Phelps and William Earle Dodge, Sr.. On March 19, 2007, it was acquired by Freeport-McMoRan and now operates under the name Freeport-McMoRan Copper & Gold Inc.-History:...

 in Bayway, New Jersey, where they were extruded into strips 0.625 inches (1.6 cm) thick, 3 inches (7.6 cm) wide and 40 feet (12.2 m) long. These were wound onto magnetic coils by Allis Chalmers in Milwaukee, Wisconsin. After the war, all the machinery was dismantled and cleaned and the floorboards beneath the machinery were ripped up and burned to recover minute amounts of silver. In the end, only 1/3,600,000th was lost. The last silver was returned in May 1970.

Responsibility for the design and construction of the electromagnetic separation plant, which came to be called Y-12
Y-12 National Security Complex
The Y-12 National Security Complex is a United States Department of Energy National Nuclear Security Administration facility located in Oak Ridge, Tennessee, near the Oak Ridge National Laboratory...

, was assigned to Stone & Webster by the S-1 Committee in June 1942. The design called for five first stage processing units, known as Alpha racetracks, and two units for final processing, known as Beta racetracks. In September 1943 Groves authorized construction of four more racetracks, known as Alpha II. Construction began in February 1943.

When the plant was started up for testing on schedule in October, the 14-ton vacuum tanks crept out of alignment because of the power of the magnets, and had to be fastened more securely. A more serious problem arose when the magnetic coils started shorting out. In December Groves ordered a magnet to be broken open, and handfuls of rust were found inside. Groves then ordered the racetracks to be torn down and the magnets sent back to the factory to be cleaned. A pickling plant was established on-site to clean the pipes and fittings. The second Alpha I was not operational until the end of January 1944, the first Beta and first and third Alpha I's came online in March, and the fourth Alpha I was operational in April. The four Alpha II racetracks were completed between July and October 1944.


Tennessee Eastman was hired to manage Y-12 on the usual cost plus fixed fee basis, with a fee of $22,500 per month plus $7,500 per racetrack for the first seven racetracks and $4,000 per additional racetrack. The calutrons were initially operated by scientists from Berkeley to remove bugs and achieve a reasonable operating rate. They were then turned over to trained Tennessee Eastman operators who had only a high school education. Nichols compared unit production data, and pointed out to Lawrence that the young "hillbilly" girl operators were outperforming his PhDs. They agreed to a production race and Lawrence lost, a morale boost for the Tennessee Eastman workers and supervisors. The girls were "trained like soldiers not to reason why", while "the scientists could not refrain from time-consuming investigation of the cause of even minor fluctuations of the dials."

Y-12 initially enriched the uranium-235 content to between 13% and 15%, and shipped the first few hundred grams of this to Los Alamos in March 1944. Only 1 part in 5,825 of the uranium feed emerged as final product. Much of the rest was splattered over equipment in the process. Strenuous recovery efforts helped raise production to 10% of the uranium-235 feed by January 1945. In February the Alpha racetracks began receiving slightly enriched (1.4%) feed from the new S-50 thermal diffusion plant. The next month it received enhanced (5%) feed from the K-25 gaseous diffusion plant. By April K-25 was producing uranium sufficiently enriched to feed directly into the Beta tracks.

Gaseous diffusion


The most promising but also the most challenging method of isotope separation was gaseous diffusion. Graham's law
Graham's law
Graham's law, known as Graham's law of effusion, was formulated by Scottish physical chemist Thomas Graham in 1846. Graham found experimentally that the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles...

 states that the rate of effusion
Effusion
In physics, effusion is the process in which individual molecules flow through a hole without collisions between molecules. This occurs if the diameter of the hole is considerably smaller than the mean free path of the molecules...

 of a gas is inversely proportional to the square root of its molecular mass
Molecular mass
The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...

, so in a box containing a semi-permeable membrane and a mixture of two gases, the lighter molecules will pass out of the container more rapidly than the heavier molecules. The gas leaving the container is somewhat enriched in the lighter molecules, while the residual gas is somewhat depleted. The idea was that such boxes could be formed into a cascade of pumps and membranes, with each successive stage containing a slightly more enriched mixture. Research into the process was carried out at Columbia University by a group that included Harold Urey, Karl P. Cohen and John R. Dunning
John R. Dunning
John Ray Dunning was an American physicist who played key roles in the development of the atomic bomb. He specialized in neutron physics and did pioneering work in gaseous diffusion for isotope separation...

.
In November 1942 the Military Policy Committee approved the construction of a 600-stage gaseous diffusion plant. On 14 December, M. W. Kellogg accepted an offer to construct the plant, which was codenamed K-25. A cost plus fixed fee contract was negotiated, eventually totaling $2.5 million. A separate corporate entity called Kellex was created for the project, headed by Percival C. Keith, one of Kellogg's vice presidents. The process faced formidable technical difficulties. The highly corrosive gas uranium hexafluoride
Uranium hexafluoride
Uranium hexafluoride , referred to as "hex" in the nuclear industry, is a compound used in the uranium enrichment process that produces fuel for nuclear reactors and nuclear weapons. It forms solid grey crystals at standard temperature and pressure , is highly toxic, reacts violently with water...

 would have to be used, as no substitute could be found, and the motors and pumps would have to be vacuum tight and enclosed in inert gas. The biggest problem was the design of the barrier, which would have to be strong, porous and resistant to corrosion by uranium hexafluoride. The best choice for this seemed to be nickel. Edward Adler and Edward Norris created a mesh barrier from electroplated nickel. A six-stage pilot plant was built at Columbia to test the process, but the Norris-Adler prototype proved to be too brittle. A rival barrier was developed from powdered nickel by Kellex, the Bell Telephone Laboratories and the Bakelite Corporation. In January 1944, Groves ordered the Kellex barrier into production.

Kellex's design for K-25 called for a four-story 0.5 mile (0.80467 km) long U-shaped structure containing 54 contiguous buildings. These were divided into nine sections. Within these were cells of six stages. The cells could be operated independently, or consecutively within a section. Similarly, the sections could be operated separately or as part of a single cascade. A survey party began construction by marking out the 500 acres (2 km²) site in May 1943. Work on the main building began in October 1943, and the six-stage pilot plant was ready for operation on 17 April 1944. In 1945 Groves canceled the upper stages of the plant, directing Kellex to instead design and build a 540-stage side feed unit, which became known as K-27. Kellex transferred the last unit to the operating contractor, Union Carbide and Carbon
Union Carbide
Union Carbide Corporation is a wholly owned subsidiary of The Dow Chemical Company. It currently employs more than 2,400 people. Union Carbide primarily produces chemicals and polymers that undergo one or more further conversions by customers before reaching consumers. Some are high-volume...

, on 11 September 1945. The total cost, including the K-27 plant completed after the war, came to $480 million.

The production plant commenced operation in February 1945, and as cascade after cascade came online, the quality of the product increased. By April 1945, K-25 had attained a 1.1% enrichment and the output of the S-50 thermal diffusion plant began being used as feed. Some product produced the next month reached nearly 7% enrichment. In August, the last of the 2,892 stages commenced operation. K-25 and K-27 achieved their full potential in the early postwar period, when they eclipsed the other production plants and became the prototypes for a new generation of plants.

Thermal diffusion



The thermal diffusion process was based on Sydney Chapman and David Enskog
David Enskog
David Enskog was a Swedish mathematical physicist. Enskog helped develop the kinetic theory of gases by extending the Maxwell–Boltzmann equations.- Biography :...

's theory, which explained that when a mixed gas passes through a temperature gradient, the heavier one tends to concentrate at the cold end and the lighter one at the warm end. Since hot gases tend to rise and cool ones tend to fall, this can be used as a means of isotope separation. This process was first demonstrated by H. Clusius and G. Dickel in Germany in 1938. It was developed by US Navy scientists, but was not one of the enrichment technologies initially selected for use in the Manhattan Project. This was primarily due to doubts about its technical feasibility, but the inter-service rivalry between the Army and Navy also played a part.


The Naval Research Laboratory continued the research under Philip Abelson's direction, but there was little contact with the Manhattan Project until April 1944, when Captain William S. Parsons, the naval officer who was in charge of ordnance development at Los Alamos, brought Oppenheimer news of encouraging progress in the Navy's experiments on thermal diffusion. Oppenheimer wrote to Groves suggesting that the output of a thermal diffusion plant could be fed into Y-12. Groves set up a committee consisting of Warren K. Lewis
Warren K. Lewis
Warren Kendall Lewis was an MIT professor who has been called the father of modern chemical engineering. He co-authored an early major textbook on the subject which essentially introduced the concept of unit operations...

, Eger Murphree and Richard Tolman to investigate the idea, and they estimated that a thermal diffusion plant costing $3.5 million could enrich 50 kilograms (110 lb) of uranium per week to nearly 0.9% uranium-235. Groves approved its construction on 24 June 1944.

Groves contracted with the H. K. Ferguson Company of Cleveland, Ohio, to build the thermal diffusion plant, which was designated S-50. Groves' advisers, Karl Cohen and W. I. Thompson from Standard Oil
Esso
Esso is an international trade name for ExxonMobil and its related companies. Pronounced , it is derived from the initials of the pre-1911 Standard Oil, and as such became the focus of much litigation and regulatory restriction in the United States. In 1972, it was largely replaced in the U.S. by...

, estimated that it would take six months to build. Groves gave Ferguson just four. Plans called for the installation of 2,142 48 feet (14.6 m) diffusion columns arranged in 21 racks. Inside each column were three concentric tubes. Steam, obtained from the nearby K-25 powerhouse at a pressure of 100 pound per square inches (689,475.7 Pa) and temperature of 545 °F (285 °C), flowed downward through the innermost 1.25 inches (3.2 cm) nickel pipe, while water at 155 °F (68.3 °C) flowed upward through the outermost iron pipe. Isotope separation occurred in the uranium hexafluoride gas between the nickel and copper pipes.

Work commenced on 9 July 1944, and S-50 began partial operation in September. Ferguson operated the plant through a subsidiary known as Fercleve. The plant produced just 10.5 pounds (4.8 kg) of 0.852% uranium-235 in October. Leaks limited production and forced shutdowns over the next few months, but in June 1945 it produced 12730 pounds (5,774.2 kg). By March 1945, all 21 production racks were operating. Initially the output of S-50 was fed into Y-12, but starting in March 1945 all three enrichment processes were run in series. S-50 became the first stage, enriching from 0.71% to 0.89%. This material was fed into the gaseous diffusion process in the K-25 plant, which produced a product enriched to about 23%. This was, in turn, fed into Y-12, which boosted it to about 89%, sufficient for nuclear weapons.

Gun-type weapon design




About 50 kilograms (110.2 lb) of uranium enriched to 89% uranium-235 was delivered to Los Alamos by July 1945. This was used to create a gun-type fission weapon
Gun-type fission weapon
Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the "gun" method: shooting one piece of sub-critical material into another...

. It worked by mechanically assembling a critical mass from two subcritical masses of uranium-235: a "bullet" and a "target". When they collided, a polonium-beryllium modulated neutron initiator would produce a burst of neutrons, which would initiate a chain reaction in the uranium-235. The configuration of the critical mass determined how much of the fissile material reacted in the interval between assembly and dispersal, and therefore the explosive yield of the bomb. Even a 1% fission of the material would result in a workable bomb, equal to thousands of tons of high explosive. A poor configuration, or slow assembly, would release enough energy to disperse the critical mass quickly, and the yield would be greatly reduced, equivalent to only a few tons of high explosive. The bomb's design was known to be inefficient and prone to accidental discharge.

The development effort on the gun-type device was carried out at Los Alamos by Parsons' O Division. Lieutenant Commander
Lieutenant commander (United States)
Lieutenant commander is a mid-ranking officer rank in the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, and the National Oceanic and Atmospheric Administration Commissioned Corps, with the pay grade of O-4 and NATO rank code OF-3...

 A. Francis Birch's group completed the design, which became Little Boy
Little Boy
"Little Boy" was the codename of the atomic bomb dropped on Hiroshima on August 6, 1945 by the Boeing B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets of the 393rd Bombardment Squadron, Heavy, of the United States Army Air Forces. It was the first atomic bomb to be used as a weapon...

, in February 1945. There was no enriched uranium available for a test. Little Boy used up all the 89% enriched uranium-235, along with some 50% enriched, averaging out to about 85% enriched. The gun-type method was considered so certain to work that no test was considered necessary, although an extensive laboratory testing program was undertaken to make sure the fundamental assumptions were correct.

Plutonium


The second line of development pursued by the Manhattan Project used the fissile element plutonium. Although small amounts of plutonium exist in nature, the best way to obtain large quantities of the element is in a nuclear reactor, in which natural uranium is bombarded by neutrons. The uranium-238 is transmuted
Nuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...

 into uranium-239, which rapidly decays, first into neptunium-239 and then into plutonium-239
Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...

. Only a small amount of the uranium-238 will be transformed, so the plutonium must be chemically separated from the remaining uranium, from any initial impurities, and from fission products.

X-10 Graphite Reactor



In March 1943, DuPont began construction of a plutonium plant on a 112 acre (0.45324832 km²) site at Oak Ridge. Intended as a pilot plant
Pilot plant
A pilot plant is a small chemical processing system which is operated to generate information about the behavior of the system for use in design of larger facilities....

 for the larger production facilities at Hanford, it included the air-cooled X-10 Graphite Reactor
X-10 Graphite Reactor
The X-10 Graphite Reactor at Oak Ridge National Laboratory in Oak Ridge, Tennessee, formerly known as the Clinton Pile and X-10 Pile, was the world's second artificial nuclear reactor and was the first reactor designed and built for continuous operation.When President Roosevelt in December 1942...

, a chemical separation plant, and support facilities. Because of the subsequent decision to construct water-cooled reactors at Hanford, only the chemical separation plant operated as a true pilot. The X-10 Graphite Reactor consisted of a huge block of graphite, 24 feet (7.3 m) long on each side, weighing around 1500 LT, surrounded by 7 feet (2.1 m) of high-density concrete as a radiation shield.

The greatest difficulty was encountered with the uranium slugs produced by Mallinckrodt and Metal Hydrides. These somehow had to be coated in aluminum to avoid corrosion and the escape of fission products into the cooling system. The Grasselli Chemical Company attempted to develop a hot dipping process without success. Meanwhile Alcoa
Alcoa
Alcoa Inc. is the world's third largest producer of aluminum, behind Rio Tinto Alcan and Rusal. From its operational headquarters in Pittsburgh, Pennsylvania, Alcoa conducts operations in 31 countries...

 tried canning. A new process for flux-less welding was developed, and 97% of the cans passed a standard vacuum test, but high temperature tests indicated a failure rate of more than 50%. Nonetheless, production began in June 1943. The Metallurgical Laboratory eventually developed an improved welding technique with the help of General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...

, which was incorporated into the production process in October 1943.

Watched by Fermi and Compton, the X-10 Graphite Reactor went critical on 4 November 1943 with about 30 LT of uranium. A week later the load was increased to 36 LT, raising its power generation to 500 kW, and by the end of the month the first 500 milligram (0.0160753731809469 ozt) of plutonium was created. Modifications over time raised the power to 4,000 kW in July 1944. X-10 operated as a production plant until January 1945, when it was turned over to research activities.

Hanford reactors


Although an air-cooled design was chosen for the reactor at Oak Ridge to facilitate rapid construction, it was recognized that this would be impractical for the much larger production reactors. Initial designs by the Metallurgical Laboratory and DuPont used helium for cooling, before they determined that a water-cooled reactor would be simpler, cheaper and quicker to build. The design did not become available until 4 October 1943; in the meantime, Matthias concentrated on improving the Hanford site by erecting accommodations, improving the roads, building a railway switch line, and upgrading the electricity, water and telephone lines.
As at Oak Ridge, the most difficulty was encountered while canning the uranium slugs, which commenced at Hanford in March 1944. They were pickled
Pickling (metal)
Tarnision is a metal surface treatment used to remove impurities, such as stains, inorganic contaminants, rust or scale from ferrous metals, copper, and aluminum alloys. A solution called Tarnision liquor, which contains strong acids, is used to remove the surface impurities...

 to remove dirt and impurities, dipped in molten bronze, tin, and aluminum-silicon alloy
Silumin
Silumin is a series of lightweight, high-strength aluminium alloys with silicon content of 13%. Among the advantages of silumin is its high resistance to corrosion, making it useful in humid environments...

, canned using hydraulic presses, and then capped using arc welding
Arc welding
Arc welding is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct or alternating current, and consumable or non-consumable electrodes...

 under an argon atmosphere. Finally, they were subjected to a series of tests to detect holes or faulty welds. Disappointingly, most canned slugs initially failed the tests, resulting in an output of only a handful of canned slugs per day. But steady progress was made and by June 1944 production increased to the point where it appeared that enough canned slugs would be available to start Reactor B
B-Reactor
The B Reactor at the Hanford Site, near Richland, Washington, USA, was the first large-scale nuclear reactor ever built. The project was commissioned to produce plutonium-239 by nuclear fission as part of the Manhattan Project, the United States nuclear weapons development program during World War II...

 on schedule in August 1944.

Work began on Reactor B, the first of six planned 250 MW reactors, on 10 October 1943. The reactor complexes were given letter designations A through F, with B, D and F sites chosen to be developed first, as this maximised the distance between the reactors. They would be the only ones constructed during the Manhattan Project. Some 390 LT of steel, 17400 cubic yards (13,303.3 m³) of concrete, 50,000 concrete blocks and 71,000 concrete bricks were used to construct the 120 feet (36.6 m) high building. Construction of the reactor itself commenced in February 1944. Watched by Compton, Matthias, DuPont's Crawford Greenewalt
Crawford Greenewalt
Crawford Hallock Greenewalt was an American chemical engineer who served as president of the DuPont Company from 1948 to 1962 and as board chairman from 1962 to 1967.-Life and career:...

, Leona Woods
Leona Woods
Leona Woods , later called Leona Woods Marshall and Leona Woods Marshall Libby, was an American physicist who helped build the first nuclear reactor and the first atomic bomb....

 and Fermi, who inserted the first slug, the reactor was powered up beginning on 13 September 1944. Over the next few days, 838 tubes were loaded and the reactor went critical. Shortly after midnight on 27 September, the operators began to withdraw the control rod
Control rod
A control rod is a rod made of chemical elements capable of absorbing many neutrons without fissioning themselves. They are used in nuclear reactors to control the rate of fission of uranium and plutonium...

s to initiate production. At first all appeared well but around 03:00 the power level started to drop and by 06:30 the reactor had shut down completely. The cooling water was investigated to see if there was a leak or contamination. The next day the reactor started up again, only to shut down once more.

Fermi contacted Chien-Shiung Wu
Chien-Shiung Wu
Chien-Shiung Wu was a Chinese-American physicist with expertise in the techniques of experimental physics and radioactivity. Wu worked on the Manhattan Project...

, who identified the cause of the problem as neutron poisoning from xenon-135
Xenon-135
Xenon-135 is an unstable isotope of xenon with a half-life of about 9.2 hours. 135Xe is a fission product of uranium and Xe-135 is the most powerful known neutron-absorbing nuclear poison , with a significant effect on nuclear reactor operation...

, which has a half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 of 9.2 hours. Fermi, Woods, Donald J. Hughes
Donald J. Hughes
Donald J. Hughes was an American nuclear physicist, chiefly notable as one of the signers of the Franck Report in June, 1945, recommending that the United States not use the atomic bomb as a weapon to prompt the surrender of Japan in World War II.Before the war Hughes worked at the Naval Ordnance...

 and John Archibald Wheeler
John Archibald Wheeler
John Archibald Wheeler was an American theoretical physicist who was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission...

 then calculated the nuclear cross section
Nuclear cross section
The nuclear cross section of a nucleus is used to characterize the probability that a nuclear reaction will occur. The concept of a nuclear cross section can be quantified physically in terms of "characteristic area" where a larger area means a larger probability of interaction...

 of xenon-135, which turned out to be 30,000 times that of uranium. Fortunately, DuPont engineer George Graves had deviated from the Metallurgical Laboratory's original design in which the reactor had 1,500 tubes arranged in a circle, and had added an additional 504 tubes to fill in the corners. The scientists had originally considered this overengineering a waste of time and money, but Fermi realized that by loading all 2,004 tubes, the reactor could reach the required power level and efficiently produce plutonium. Reactor D was started on 17 December 1944 and Reactor F on 25 February 1945.

Separation process



Meanwhile, the chemists considered the problem of how plutonium could be separated from uranium when its chemical properties were not known. Working with the minute quantities of plutonium available at the Metallurgical Laboratory in 1942, a team under Charles M. Cooper developed a lanthanum fluoride process
Fluoride selective electrode
A fluoride selective electrode is a type of ion selective electrode sensitive to the concentration of the fluoride ion. A common example is the lanthanum fluoride electrode.-Lanthanum fluoride electrode:...

 for separating uranium and plutonium, which was chosen for the pilot separation plant. A second separation process, the bismuth phosphate process
Bismuth phosphate process
Bismuth-phosphate process was a process used to extract plutonium from used nuclear fuel taken from nuclear reactors. This process was used to produce all the plutonium of the atomic bomb dropped on Nagasaki in 1945. In 1952 this process was replaced by the Redox and PUREX processes.-References:*...

, was subsequently developed by Seaborg and Stanly G. Thomson. This process worked by toggling plutonium between its +4 and +6 oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...

s in solutions of bismuth phosphate. In the former state, the plutonium was precipitated; in the latter, it stayed in solution and the other products were precipitated.

Greenewalt favored the bismuth phosphate process due to the corrosive nature of lanthanum fluoride, and it was selected for the Hanford separation plants. Once X-10 began producing plutonium, the pilot separation plant was put to the test. The first batch was processed at 40% efficiency but over the next few months this was raised to 90%.

At Hanford, top priority was initially given to the installations in the 300 area. This contained buildings for testing materials, preparing uranium, and assembling and calibrating instrumentation. One of the buildings housed the canning equipment for the uranium slugs, while another contained a small test reactor. Notwithstanding the high priority allocated to it, work on the 300 area fell behind schedule due to the unique and complex nature of the 300 area facilities, and wartime shortages of labor and materials.

Early plans called for the construction of two separation plants in each of the areas known as 200-West and 200-East. This was subsequently reduced to two, the T and U plants, in 200-West and one, the B plant, at 200-East. Each separation plant consisted of four buildings: a process cell building or "canyon" (known as 221), a concentration building (224), a purification building (231) and a magazine store (213). The canyons were each 800 feet (243.8 m) long and 65 feet (19.8 m) wide. Each consisted of forty 17.7 feet (5.4 m) by 13 feet (4 m) by 20 feet (6.1 m) cells.

Work began on 221-T and 221-U in January 1944, with the former completed in September and the latter in December. The 221-B building followed in March 1945. Because of the high levels of radioactivity involved, all work in the separation plants had to be conducted by remote control using closed-circuit television, something unheard of in 1943. Maintenance was carried out with the aid of an overhead crane and specially designed tools. The 224 buildings were smaller because they had less material to process, and it was less radioactive. The 224-T and 224-U buildings were completed on 8 October 1944, and 224-B followed on 10 February 1945. The purification methods that were eventually used in 231-W were still unknown when construction commenced on 8 April 1944, but the plant was complete and the methods were selected by the end of the year. On 5 February 1945, Matthias hand-delivered the first shipment of 80 grams (2.6 ozt) of 95%-pure plutonium nitrate to a Los Alamos courier in Los Angeles.

Weapon design



In 1943, development efforts were directed to a gun-type fission weapon with plutonium called Thin Man. Initial research on the properties of plutonium was done using cyclotron-generated plutonium-239, which was extremely pure, but could only be created in very small amounts. Los Alamos received the first sample of plutonium from the Clinton X-10 reactor in April 1944 and within days Emilio Segrè discovered a problem: the reactor-bred plutonium had a higher concentration of plutonium-240, resulting in up to five times the spontaneous fission rate of cyclotron plutonium. Seaborg had correctly predicted in March 1943 that some of the plutonium-239 would absorb a neutron and become plutonium-240.

This made reactor plutonium unsuitable for use in a gun-type weapon. The plutonium-240 would start the chain reaction too quickly, causing a predetonation that would release enough energy to disperse the critical mass with a minimal amount of plutonium reacted (a fizzle
Fizzle (nuclear test)
In nuclear weapons, a fizzle occurs when the testing of a nuclear bomb fails to meet its expected yield. The reason for the failure can be linked to improper bomb design, poor construction, or lack of expertise. All countries that have had a nuclear weapons testing program have experienced fizzles...

). A faster gun was suggested but found to be impractical. The possibility of separating the isotopes was considered and rejected, as plutonium-240 is even harder to separate from plutonium-239 than uranium-235 from uranium-238.

Work on an alternative method of bomb design, known as implosion, had begun earlier at the instigation of the physicist Seth Neddermeyer
Seth Neddermeyer
Seth Henry Neddermeyer was an American physicist who co-discovered the muon, and later championed the implosion design of the plutonium atomic bomb, at the Manhattan Project....

. Implosion used explosives to crush a subcritical sphere of fissile material into a smaller and denser form. When the fissile atoms are packed closer together, the rate of neutron capture increases, and the mass becomes a critical mass. The metal needs to travel only a very short distance, so the critical mass is be assembled in much less time than it would take with the gun method. Neddermeyer's 1943 and early 1944 investigations into implosion showed promise, but also made it clear that the problem would be much more difficult from a theoretical and engineering perspective than the gun design. In September 1943, John von Neumann
John von Neumann
John von Neumann was a Hungarian-American mathematician and polymath who made major contributions to a vast number of fields, including set theory, functional analysis, quantum mechanics, ergodic theory, geometry, fluid dynamics, economics and game theory, computer science, numerical analysis,...

, who had experience with shaped charge
Shaped charge
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...

s used in armor-piercing shells, argued that not only would implosion reduce the danger of predetonation and fizzle, but would make more efficient use of the fissionable material. He proposed using a spherical configuration instead of the cylindrical one that Neddermeyer was working on.


By July 1944, Oppenheimer had concluded plutonium could not be used in a gun design, and opted for implosion. The accelerated effort on an implosion design, codenamed Fat Man
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...

, began in August 1944 when Oppenheimer implemented a sweeping reorganization of the Los Alamos laboratory to focus on implosion. Two new groups were created at Los Alamos to develop the implosion weapon, X (for explosives) Division headed by George Kistiakowsky
George Kistiakowsky
George Bogdan Kistiakowsky was a Ukrainian-American chemistry professor at Harvard who participated in the Manhattan Project and later served as President Eisenhower's Science Advisor...

 and G (for gadget) Division under Robert Bacher. The new design that von Neumann and T (for theoretical) Division, most notably Rudolf Peierls, had come up with used explosive lens
Explosive lens
An explosive lens—as used, for example, in nuclear weapons—is a highly specialized explosive charge, a special type of a shaped charge. In general, it is a device composed of several explosive charges that are shaped in such a way as to change the shape of the detonation wave passing through it,...

es to focus the explosion onto a spherical shape using a combination of slow and fast high explosives.

The design of lenses that detonated with just the right shape and velocity turned out to be slow, difficult and frustrating. Various explosives were tested before settling on composition B
Composition B
Composition B, colloquially "comp B", is an explosive consisting of castable mixtures of RDX and TNT. It is used as the main explosive filling in artillery projectiles, rockets, land mines, hand grenades, sticky bombs and various other munitions...

 as the fast explosive and baratol as the slow explosive. The final design resembled a soccer ball, with 20 hexagonal and 12 pentagonal lenses, each weighing about 80 pounds (36.3 kg). Getting the detonation just right required fast, reliable and safe electrical detonator
Detonator
A detonator is a device used to trigger an explosive device. Detonators can be chemically, mechanically, or electrically initiated, the latter two being the most common....

s, of which there were two for each lens for reliability. It was therefore decided to use exploding-bridgewire detonator
Exploding-bridgewire detonator
The exploding-bridgewire detonator is a type of detonator used to initiate the detonation reaction in explosive materials, similar to a blasting cap in that it is fired using an electric current...

s. A contract for their manufacture was given to Raytheon
Raytheon
Raytheon Company is a major American defense contractor and industrial corporation with core manufacturing concentrations in weapons and military and commercial electronics. It was previously involved in corporate and special-mission aircraft until early 2007...

. To study the behavior of converging shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

s, Serber devised the RaLa Experiment
RaLa Experiment
The RaLa Experiment, or RaLa, was a series of tests during and after the Manhattan Project designed to study the behavior of converging shock waves to achieve the spherical implosion necessary for compression of the plutonium pit of the nuclear weapon...

, which used the short-lived radioisotope lanthanum-140, a potent source of gamma radiation, in an ionization chamber
Ionization chamber
The ionization chamber is the simplest of all gas-filled radiation detectors, and is used for the detection or measurement of ionizing radiation...

.

Within the explosives was the 4.5 inch thick aluminum pusher, which provided a smooth transition from the relatively low density explosive to the next layer, the 3 inch thick tamper of natural uranium. Its main job was to hold the critical mass together for as long as possible. It would also reflect neutrons back into the core. Some part of it might fission as well. To prevent predetonation by an external neutron, the tamper was coated in a thin layer of boron. A polonium-beryllium modulated neutron initiator, known as an "urchin" because its shape resembled a sea urchin, was developed by the Monsanto Company to start the chain reaction at precisely the right moment. This work with the chemistry and metallurgy of radioactive polonium was directed by Charles Allen Thomas
Charles Allen Thomas
Charles Allen Thomas was a noted American chemist and businessman, and an important figure in the Manhattan Project....

 and became known as the Dayton Project
Dayton Project
The Dayton Project was one of several sites involved in the Manhattan Project to build the first atomic bombs. Charles Allen Thomas, an executive of the Monsanto Company corporation, was assigned to develop the neutron generating devices that triggered the nuclear detonation of the atomic bombs...

. Testing required up to 500 curies per month of polonium, which Monsanto was able to deliver. The whole assembly was encased in a duralumin
Duralumin
Duralumin is the trade name of one of the earliest types of age-hardenable aluminium alloys. The main alloying constituents are copper, manganese, and magnesium. A commonly used modern equivalent of this alloy type is AA2024, which contains 4.4% copper, 1.5% magnesium, 0.6% manganese and 93.5%...

 bomb casing to protect it from bullets and flak.
The ultimate task of the metallurgists was to figure out how to cast plutonium into a sphere. The difficulties became apparent when attempts to measure the density of plutonium gave inconsistent results. At first contamination was believed to be the cause, but it was soon determined that there were multiple allotropes of plutonium
Allotropes of plutonium
Even at ambient pressure, plutonium occurs in a variety of allotropes. These allotropes differ widely in crystal structure and density; the α and δ allotropes differ in density by more than 25% at constant pressure....

. The brittle α phase that exists at room temperature changes to the plastic β phase at higher temperatures. Attention then shifted to the even more malleable δ phase that normally exists in the 300 °C to 450 °C range. It was found that this was stable at room temperature when alloyed with aluminum, but aluminum emits neutrons when bombarded with alpha particles, which would exacerbate the pre-ignition problem. The metallurgists then hit upon a plutonium-gallium alloy
Plutonium-gallium alloy
Plutonium-gallium alloy is an alloy of plutonium and gallium, used in nuclear weapon pits – the component of a nuclear weapon where the fission chain reaction is started....

, which stabilized the δ phase and could be hot pressed
Hot pressing
Hot pressing is a high-pressure, low-strain-rate powder metallurgy process for forming of a powder or powder compact at a temperature high enough to induce sintering and creep processes. This is achieved by the simultaneous application of heat and pressure....

 into the desired spherical shape. As plutonium was found to corrode readily, the sphere was coated with nickel.

The work proved dangerous. By the end of the war, half the experienced chemists and metallurgists had to be removed from work with plutonium when unacceptably high levels of the element appeared in their urine. A minor fire at Los Alamos in January 1945 led to a fear that a fire in the plutonium laboratory might contaminate the whole town, and Groves authorized the construction of a new facility for plutonium chemistry and metallurgy, which became known as the DP-site. The hemispheres for the first plutonium pit
Pit (nuclear weapon)
The pit is the core of an implosion weapon – the fissile material and any neutron reflector or tamper bonded to it. Some weapons tested during the 1950s used pits made with U-235 alone, or in composite with plutonium, but all-plutonium pits are the smallest in diameter and have been the standard...

 (or core) were produced and delivered on 2 July 1945. Three more hemispheres followed on 23 July and were delivered three days later.

Trinity



Because of the complexity of an implosion-style weapon, it was decided that, despite the waste of fissile material, an initial test would be required. Groves approved the test, subject to the active material being recovered. Consideration was therefore given to a controlled fizzle
Fizzle (nuclear test)
In nuclear weapons, a fizzle occurs when the testing of a nuclear bomb fails to meet its expected yield. The reason for the failure can be linked to improper bomb design, poor construction, or lack of expertise. All countries that have had a nuclear weapons testing program have experienced fizzles...

, but Oppenheimer opted instead for a full-scale nuclear test, codenamed "Trinity".


In March 1944, planning for the test was assigned to Kenneth Bainbridge
Kenneth Bainbridge
Kenneth Tompkins Bainbridge was an American physicist at Harvard University who did work on cyclotron research. His precise measurements of mass differences between nuclear isotopes allowed him to confirm Albert Einstein's mass-energy equivalence concept. He was the Director of the Trinity test of...

, a professor of physics at Harvard, working under Kistiakowsky. Bainbridge selected the bombing range near Alamogordo Army Airfield as the site for the test. Bainbridge worked with Captain Samuel P. Davalos on the construction of the Trinity Base Camp and its facilities, which included barracks, warehouses, workshops, an explosive magazine and a commissary.

Groves did not relish the prospect of explaining the loss of a billion dollars worth of plutonium to a Senate committee, so a cylindrical containment vessel codenamed "Jumbo" was constructed to recover the active material in the event of a failure. Measuring 25 feet (7.6 m) long and 12 feet (3.7 m) wide, it was fabricated at great expense from 214 LT of iron and steel by Babcock & Wilcox in Barberton, Ohio. Brought in a special railroad car to a siding in Pope, New Mexico, it was transported the last 25 miles (40.2 km) to the test site on a trailer pulled by two tractors. By the time it arrived, however, confidence in the implosion method was high enough, and the availability of plutonium was sufficient, that Oppenheimer decided not to use it. Instead, it was placed atop a steel tower 800 yards (731.5 m) from the weapon as a rough measure of how powerful the explosion would be. In the end, Jumbo survived, although its tower did not, adding credence to the belief that Jumbo would have successfully contained a fizzled explosion.

A pre-test explosion was conducted on 7 May 1945 to calibrate the instruments. A wooden test platform was erected 800 yards (731.5 m) from Ground Zero and piled with 100 LT of TNT spiked with nuclear fission products in the form of an irradiated uranium slug from Hanford, which was dissolved and poured into tubing inside the explosive. This explosion was observed by Oppenheimer and Groves's new deputy commander, Brigadier General Thomas Farrell. The pre-test produced data that proved vital for the Trinity test.

For the actual test, the weapon, nicknamed "the gadget", was hoisted to the top of a 100 feet (30.5 m) steel tower, as detonation at that height would give a better indication of how the weapon would behave when dropped from a bomber. Detonation in the air maximized the energy applied directly to the target, and generated less nuclear fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...

. The gadget was assembled under the supervision of Norris Bradbury
Norris Bradbury
Norris Edwin Bradbury , was an American physicist who was born in Santa Barbara, California. He served as director of the Los Alamos National Laboratory for 25 years , succeeding J. Robert Oppenheimer, who personally chose Bradbury for the position of director after working closely with him on the...

 at the nearby McDonald Ranch House
McDonald Ranch House
The McDonald Ranch House was the location of assembly for the first tested nuclear weapon. The test occurred on July 16, 1945; a plutonium bomb was tested, the type of weapon later dropped on Nagasaki, Japan...

 on 13 July, and precariously winched up the tower the following day. Observers included Bush, Chadwick, Conant, Farrell, Fermi, Groves, Lawrence, Oppenheimer and Tolman. At 05:30 on 16 July 1945 the gadget exploded with an energy equivalent
TNT equivalent
TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...

 of around 20 kilotons of TNT, leaving a crater of Trinitite
Trinitite
Trinitite, also known as Atomsite or Alamogordo Glass, is the name given to the glassy residue left on the desert floor after the plutonium-based Trinity nuclear bomb test on July 16, 1945, near Alamogordo, New Mexico...

 (radioactive glass) in the desert 250 feet (76.2 m) wide. The shock wave was felt over 100 mi away, and the mushroom cloud
Mushroom cloud
A mushroom cloud is a distinctive pyrocumulus mushroom-shaped cloud of condensed water vapor or debris resulting from a very large explosion. They are most commonly associated with nuclear explosions, but any sufficiently large blast will produce the same sort of effect. They can be caused by...

 reached 7.5 miles (12.1 km) in height. It was heard as far away as El Paso, Texas
El Paso, Texas
El Paso, is a city in and the county seat of El Paso County, Texas, United States, and lies in far West Texas. In the 2010 census, the city had a population of 649,121. It is the sixth largest city in Texas and the 19th largest city in the United States...

, so Groves issued a cover story about an ammunition magazine explosion at Alamogordo Field.

Personnel


In June 1944, the Manhattan Project employed some 129,000 workers, of whom 84,500 were construction workers, 40,500 were plant operators and 1,800 were military personnel. As construction activity fell off, the workforce declined to 100,000 a year later, but the number of military personnel increased to 5,600. Procuring the required numbers of workers, especially highly skilled workers, in competition with other vital wartime programs proved very difficult. In 1943, Groves obtained a special temporary priority for labor from the War Manpower Commission
War Manpower Commission
The War Manpower Commission was a World War II agency of the United States Government charged with planning to balance the labor needs of agriculture, industry and the armed forces. It was created by President Franklin D. Roosevelt in Executive Order 9139 of April 18, 1942. Its chairman was Paul V...

. In March 1944, both the War Production Board and the War Manpower Commission gave the project their highest priority.
Tolman and Conant, in their role as the project's scientific advisers, drew up a list of candidate scientists and had them rated by scientists already working on the project. Groves then sent a personal letter to the head of their university or company asking for them to be released for essential war work. At the University of Wisconsin–Madison
University of Wisconsin–Madison
The University of Wisconsin–Madison is a public research university located in Madison, Wisconsin, United States. Founded in 1848, UW–Madison is the flagship campus of the University of Wisconsin System. It became a land-grant institution in 1866...

, Stanisław Ulam gave one of his students, Joan Hinton
Joan Hinton
Joan Hinton was a nuclear physicist and one of the few women who worked for the Manhattan Project in Los Alamos. She lived in the People's Republic of China after 1949, where she and her husband Erwin Engst participated in China’s efforts at developing a socialist economy, working extensively in...

, an exam early, so she could leave to do war work. A few weeks later, Ulam received a letter from Hans Bethe, inviting him to join the project. Conant personally persuaded the explosives expert George Kistiakowsky to join the project.

One source of skilled personnel was the Army itself, particularly the Army Specialized Training Program
Army Specialized Training Program
The Army Specialized Training Program was a military training program instituted by the United States Army during World War II at a number of American universities to meet wartime demands for junior officers and soldiers with technical skills...

. In 1943, the MED created the Special Engineer Detachment (SED), with an authorized strength of 675. Technicians and skilled workers drafted into the Army were assigned to the SED. Another source was the Women's Army Corps (WAC). Initially intended for clerical tasks handling classified material, the WACs were soon tapped for technical and scientific tasks as well. On 1 February 1945, all military personnel assigned to the MED, including all SED detachments, were assigned to the 9812th Technical Service Unit, except at Los Alamos, where military personnel other than SED, including the WACs and Military Police, were assigned to the 4817th Service Command Unit.

An Associate Professor of Radiology
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...

 at the University of Rochester School of Medicine, Stafford L. Warren
Stafford L. Warren
Stafford Leak Warren was an American physician and radiologist who was a pioneer in the field of nuclear medicine and best known for his invention of the mammogram...

, was commissioned as a colonel in the United States Army Medical Corps, and appointed as chief of the MED's Medical Section and Groves' medical advisor. Warren's initial task was to staff hospitals at Oak Ridge, Richland and Los Alamos. The Medical Section was responsible for medical research, but also for the MED's health and safety programs. This presented an enormous challenge, because workers were handling a variety of toxic chemicals, using hazardous liquids and gases under high pressures, working with high voltages, and performing experiments involving explosives, not to mention the largely unknown dangers presented by radioactivity and handling fissile materials. Yet in December 1945, the National Safety Council
National Safety Council
The National Safety Council is a 501 nonprofit, nongovernmental public service organization dedicated to protecting life and promoting health. Headquartered in Itasca, Illinois, NSC is a member organization, founded in 1913 and granted a congressional charter in 1953...

 presented the Manhattan Project with the Award of Honor for Distinguished Service to Safety in recognition of its safety record. Between January 1943 and June 1945, there were 62 fatalities and 3,879 disabling injuries, which was about 62 percent below the rate of private industry.

Espionage


The Manhattan Project operated under a blanket of tight security lest its discovery induce Axis powers, especially Germany, to accelerate their own nuclear projects or undertake covert operations against the project. The prospect of sabotage was always present, and sometimes suspected when there were equipment failures. While there were some problems believed to be the result of careless or disgruntled employees, there were no confirmed instances of Axis-instigated sabotage. However, on 10 March 1945, a Japanese fire balloon
Fire balloon
A , or Fu-Go, was a weapon launched by Japan during World War II. A hydrogen balloon with a load varying from a incendiary to one antipersonnel bomb and four incendiary devices attached, they were designed as a cheap weapon intended to make use of the jet stream over the Pacific Ocean and wreak...

 struck a power line, and the resulting power surge caused the three reactors at Hanford to be temporarily shut down.

With so many people involved, security was a difficult task. A special Counter Intelligence Corps
Counter Intelligence Corps
The Counter Intelligence Corps was a World War II and early Cold War intelligence agency within the United States Army. Its role was taken over by the U.S. Army Intelligence Corps in 1961 and, in 1967, by the U.S. Army Intelligence Agency...

 detachment was formed to handle the project's security issues. By 1943, it was clear that the Soviet Union was attempting to penetrate the project. Lieutenant Colonel Boris T. Pash, the head of the Counter Intelligence Branch of the Western Defense Command
Western Defense Command
Western Defense Command was established on 17 March 1941 as the command formation of the U.S. Army responsible for coordinating the defense of the Pacific Coast region of the United States. A second major responsibility was the training of soldiers prior to their deployment overseas. The first...

, investigated suspected Soviet espionage at the Radiation Laboratory in Berkeley. Oppenheimer informed Pash that he had been approached by a fellow professor at Berkeley, Haakon Chevalier
Haakon Chevalier
Haakon Maurice Chevalier was an author, translator, and professor of French literature at the University of California, Berkeley best known for his friendship with physicist J...

, about passing information to the Soviet Union.

The most successful Soviet spy was Klaus Fuchs
Klaus Fuchs
Klaus Emil Julius Fuchs was a German theoretical physicist and atomic spy who in 1950 was convicted of supplying information from the American, British and Canadian atomic bomb research to the USSR during and shortly after World War II...

, a member of the British Mission who played an important part at Los Alamos. The 1950 revelation of Fuchs' espionage activities damaged the United States' nuclear cooperation with Britain and Canada. Subsequently, other instances of espionage were uncovered, leading to the arrest of Harry Gold
Harry Gold
Harry Gold was a laboratory chemist who was convicted of being the “courier” for a number of Soviet spy rings during the Manhattan Project.-Early life:Gold was born in Switzerland to poor Russian Jewish immigrants...

, David Greenglass
David Greenglass
David Greenglass was an atomic spy for the Soviet Union who worked in the Manhattan project. He was the brother of Ethel Rosenberg.-Biography:...

 and Ethel and Julius Rosenberg. Other spies like George Koval and Theodore Hall
Theodore Hall
Theodore Alvin Hall was an American physicist and an atomic spy for the Soviet Union, who, during his work on US efforts to develop the first atomic bomb during World War II , gave a detailed description of the "Fat Man" plutonium bomb, and of processes for purifying plutonium, to Soviet...

 remained unknown for decades. The value of the espionage is difficult to quantify, as the principal constraint on the Soviet atomic bomb project
Soviet atomic bomb project
The Soviet project to develop an atomic bomb , was a clandestine research and development program began during and post-World War II, in the wake of the Soviet Union's discovery of the United States' nuclear project...

 was a shortage of uranium ore. The consensus is that espionage saved the Soviets one or two years of effort.

Foreign intelligence



In addition to developing the atomic bomb, the Manhattan Project was charged with gathering intelligence on the German nuclear energy project
German nuclear energy project
The German nuclear energy project, , was an attempted clandestine scientific effort led by Germany to develop and produce the atomic weapons during the events involving the World War II...

. It was believed that the Japanese atomic program
Japanese atomic program
The Japanese program to develop nuclear weapons was conducted during World War II. Like the German nuclear weapons program, it suffered from an array of problems, and was ultimately unable to progress beyond the laboratory stage before the atomic bombings of Hiroshima and Nagasaki and the Japanese...

 was not far advanced because Japan had little access to uranium ore, but it was initially feared that Germany was very close to developing its own weapons. At the instigation of the Manhattan Project, a bombing and sabotage campaign
Norwegian heavy water sabotage
The Norwegian heavy water sabotage was a series of actions undertaken by Norwegian saboteurs during World War II to prevent the German nuclear energy project from acquiring heavy water , which could be used to produce nuclear weapons...

 was carried out against heavy water plants in German-occupied Norway. A small mission was created, jointly staffed by the Office of Naval Intelligence
Office of Naval Intelligence
The Office of Naval Intelligence was established in the United States Navy in 1882. ONI was established to "seek out and report" on the advancements in other nations' navies. Its headquarters are at the National Maritime Intelligence Center in Suitland, Maryland...

, OSRD, the Manhattan Project, and Army Intelligence (G-2), to investigate enemy scientific developments. It was not restricted to those involving nuclear weapons. The Chief of Army Intelligence, Major General George V. Strong, appointed Boris Pash to command the unit, which was codenamed "Alsos", a Greek word meaning "grove".


The Alsos Mission to Italy questioned staff of the physics laboratory at the University of Rome following the capture of the city in June 1944. Meanwhile Pash formed a combined British and American Alsos mission in London under the command of Captain Horace K. Calvert to participate in Operation Overlord
Operation Overlord
Operation Overlord was the code name for the Battle of Normandy, the operation that launched the invasion of German-occupied western Europe during World War II by Allied forces. The operation commenced on 6 June 1944 with the Normandy landings...

. Groves considered the risk that the Germans might attempt to disrupt the Normandy landings with radioactive poisons was sufficient to warn General Dwight D. Eisenhower
Dwight D. Eisenhower
Dwight David "Ike" Eisenhower was the 34th President of the United States, from 1953 until 1961. He was a five-star general in the United States Army...

 and send an officer to brief his chief of staff, Lieutenant General Walter Bedell Smith
Walter Bedell Smith
Walter Bedell "Beetle" Smith was a senior United States Army general who served as General Dwight D. Eisenhower's chief of staff at Allied Forces Headquarters during the Tunisia Campaign and the Allied invasion of Italy...

. Under the codename Operation Peppermint, special equipment was prepared and Chemical Warfare Service teams were trained in its use.

Following in the wake of the advancing Allied armies, Pash and Calvert interviewed Frédéric Joliot-Curie
Frédéric Joliot-Curie
Jean Frédéric Joliot-Curie , born Jean Frédéric Joliot, was a French physicist and Nobel laureate.-Early years:...

 about the activities of German scientists. They spoke to officials at Union Minière du Haut Katanga
Union Minière du Haut Katanga
The Union Minière du Haut Katanga was a Belgian mining company, once operating in Katanga, in what is now the Democratic Republic of the Congo...

 about uranium shipments to Germany. They tracked down 68 tons of ore in Belgium and 30 tons in France. The interrogation of German prisoners indicated that uranium and thorium were being processed in Oranienburg
Oranienburg
Oranienburg is a town in Brandenburg, Germany. It is the capital of the district of Oberhavel.- Geography :Oranienburg is a town located on the banks of the Havel river, 35 km north of the centre of Berlin.- Division of the town :...

, so Groves arranged for it to be bombed on 15 March 1945. An Alsos team went to Stassfurt in the Soviet Occupation Zone and retrieved 11 tons of ore from WIFO
WIFO
Wirtschaftliche Forschungsgesellschaft was a Nazi Germany-owned company "charged with the construction and operation of solid fuel storage depots."-Chronology:...

. In April 1945, Pash, in command of a composite force known as T-Force, conducted Operation Harborage
Operation Harborage
During the final days of World War II, Operation Harborage was part of the overall Allied operation to capture German atomic weapons scientists, material and facilities....

, a sweep behind enemy lines of the cities of Hechingen
Hechingen
Hechingen is a town in central Baden-Württemberg, Germany. It is situated about south of the state capital of Stuttgart and north of Lake Constance and the Swiss border.- City districts :...

, Bisingen
Bisingen
Bisingen is a municipality in the Zollernalbkreis district, in Baden-Württemberg, Germany.- References :...

 and Haigerloch
Haigerloch
-Geography:-Geographical situation:Haigerloch lies at between 430 and 550 metres elevation in the valley of the Eyach, which forms two loops in a steep shelly limestone valley...

 that were the heart of the German nuclear effort. T-Force captured the nuclear laboratories, documents, equipment and supplies, including heavy water and 1.5 tons of metallic uranium.

Alsos teams rounded up German scientists including Kurt Diebner
Kurt Diebner
Kurt Diebner was a German nuclear physicist who is well known for directing and administrating the German nuclear energy project, a secretive program aiming to built weapon of mass destruction for the Nazi Germany during the course of World War II...

, Otto Hahn
Otto Hahn
Otto Hahn FRS was a German chemist and Nobel laureate, a pioneer in the fields of radioactivity and radiochemistry. He is regarded as "the father of nuclear chemistry". Hahn was a courageous opposer of Jewish persecution by the Nazis and after World War II he became a passionate campaigner...

, Walther Gerlach, Werner Heisenberg
Werner Heisenberg
Werner Karl Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...

 and Carl Friedrich von Weizsäcker
Carl Friedrich von Weizsäcker
Carl Friedrich Freiherr von Weizsäcker was a German physicist and philosopher. He was the longest-living member of the research team which performed nuclear research in Germany during the Second World War, under Werner Heisenberg's leadership...

, who were taken to England where they were interned at Farm Hall, a bugged house in Godmanchester
Godmanchester
Godmanchester is a small town and civil parish within the Huntingdonshire district of Cambridgeshire, in England. It lies on the south bank of the River Great Ouse, south of the larger town of Huntingdon, and on the A14 road....

. After the bombs were detonated in Japan, Heisenberg figured out what the Allies had done, and explained it to other imprisoned nuclear project physicists (and the hidden microphones).

Preparations


Starting in November 1943, the Army Air Forces Materiel Command
Air Force Materiel Command
Air Force Materiel Command is a major command of the United States Air Force. AFMC was created July 1, 1992 through the reorganization of Air Force Logistics Command and Air Force Systems Command....

 at Wright Field
Wright Field
Wright Field was an airfield of the United States Army Air Corps and Air Forces near Riverside, Ohio. From 1927 to 1947 it was the research and development center for the Air Corps, and during World War II a flight test center....

, Ohio, began Silverplate
Silverplate
Silverplate was the code reference for the United States Army Air Forces participation in the Manhattan Project during World War II. Originally the name for the aircraft modification project for the B-29 Superfortress to enable it to drop an atomic weapon, Silverplate eventually came to identify...

, the codename modification of B-29s to carry the bombs. Test drops were carried out at Muroc Army Air Field
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...

, California, and the Naval Ordnance Test Station at Inyokern, California
Naval Air Weapons Station China Lake
- About : is part of under Commander, Navy Installation Command and is located in the Western Mojave Desert region of California, approximately north of Los Angeles. Occupying three counties – Kern, San Bernardino and Inyo – the installation’s closest neighbors are the cities of Ridgecrest,...

. Groves met with the Chief of United States Army Air Forces
United States Army Air Forces
The United States Army Air Forces was the military aviation arm of the United States of America during and immediately after World War II, and the direct predecessor of the United States Air Force....

 (USAAF), General Henry H. Arnold
Henry H. Arnold
Henry Harley "Hap" Arnold was an American general officer holding the grades of General of the Army and later General of the Air Force. Arnold was an aviation pioneer, Chief of the Air Corps , Commanding General of the U.S...

, in March 1944 to discuss the delivery of the finished bombs to their targets. The only Allied aircraft capable of carrying the 17 feet (5.2 m) long Thin Man or the 59 inches (149.9 cm) wide Fat Man was the British Avro Lancaster
Avro Lancaster
The Avro Lancaster is a British four-engined Second World War heavy bomber made initially by Avro for the Royal Air Force . It first saw active service in 1942, and together with the Handley Page Halifax it was one of the main heavy bombers of the RAF, the RCAF, and squadrons from other...

, but using a British aircraft would have caused difficulties with maintenance. Groves hoped that the American Boeing B-29 Superfortress could be modified to carry Thin Man by joining its two bomb bay
Bomb bay
The bomb bay or weapons bay on some military aircraft is a compartment to carry bombs, usually in the aircraft's fuselage, with "bomb bay doors" which open at the bottom. The bomb bay doors are opened and the bombs are dropped when over the target or at a specified launching point.Large-sized...

s together. Arnold promised that no effort would be spared to modify B-29s to do the job, and designated Major General Oliver P. Echols
Oliver P. Echols
Oliver Patton Echols was an American military officer who brought success in World War II to the United States Army Air Forces by expanding the inventory of America's air arm to meet the needs of the coming war. More than any other man under Chief of the Army Air Forces, General Henry H...

 as the USAAF liaison to the Manhattan Project. In turn, Echols named Colonel Roscoe C. Wilson as his alternative, and Wilson became Manhattan Project's main USAAF contact. President Roosevelt instructed Groves that if the atomic bombs were ready before the war with Germany ended, he should be ready to drop them on Germany.


The 509th Composite Group
509th Composite Group
The 509th Composite Group was a United States Army Air Forces unit created during World War II, and tasked with operational deployment of nuclear weapons...

 was activated on 17 December 1944 at Wendover Army Air Field, Utah, under the command of Colonel Paul W. Tibbets. This base, close to the border with Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...

, was codenamed "Kingman" or "W-47". Training was conducted at Wendover and at Batista Army Airfield
Batista Army Airfield
San Antonio de los Baños Air Base is a military air base located near San Antonio de los Baños, a municipality in the province of Havana in Cuba. It is located approximately southwest of the city of San Antonio de los Baños, about southwest of Havana.- 1942 :The station was built in 1942 and...

, Cuba, where the 393d Bombardment Squadron
393d Bomb Squadron
The 393d Bomb Squadron is part of the 509th Bomb Wing at Whiteman Air Force Base, Missouri.-History:Activated as a B-29 Superfortress squadron in early 1944; trained under Second Air Force. Training delayed as engineering flaws being worked out of the B-29...

 practiced long-distance flights over water, and dropping dummy pumpkin bomb
Pumpkin bomb
Pumpkin bombs were conventional high explosive aerial bombs developed by the Manhattan Project and used by the United States Army Air Forces against Japan during World War II...

s. A special unit known as Alberta
Project Alberta
Project Alberta was a section of the Manhattan Project which developed the means of delivering the first atomic bombs, used by the United States Army Air Forces against the Empire of Japan during World War II...

 was formed at Los Alamos under Captain William S. Parsons as part of the Manhattan Project to assist in preparing and delivering the bombs. Commander Frederick L. Ashworth from Alberta met with Fleet Admiral Chester W. Nimitz on Guam
Guam
Guam is an organized, unincorporated territory of the United States located in the western Pacific Ocean. It is one of five U.S. territories with an established civilian government. Guam is listed as one of 16 Non-Self-Governing Territories by the Special Committee on Decolonization of the United...

 in February 1945 to inform him of the project. While he was there, Ashworth selected North Field
North Field (Tinian)
North Field is a former World War II airfield on Tinian in the Mariana Islands. Abandoned after the war, today North Field is a tourist attraction....

 on the Pacific Island Tinian
Tinian
Tinian is one of the three principal islands of the Commonwealth of the Northern Mariana Islands.-Geography:Tinian is about 5 miles southwest of its sister island, Saipan, from which it is separated by the Saipan Channel. It has a land area of 39 sq.mi....

 as a base for the 509th Composite Group, and reserved space for the group and its buildings. The group deployed there in July 1945. Farrell arrived at Tinian on 30 July as the Manhattan Project representative.

Most of the components for Little Boy left San Francisco on the cruiser on 16 July and arrived on Tinian on 26 July. Four days later the ship was sunk by a Japanese submarine. The remaining components, which included some uranium-235, were delivered by three C-54 Skymasters of the Air Transport Command
Air Transport Command
Air Transport Command is an inactive United States Air Force unit. Its mission was to meet the urgent demand for the speedy reinforcement of the United States' military bases worldwide during World War II, using an air supply system to supplement surface transport...

. Two Fat Man assemblies travelled to Tinian in specially modified 509th Composite Group B-29s. The first plutonium core went in a special C-54. A joint targeting committee of the Manhattan District and USAAF was established to determine which cities in Japan should be targets, and recommended Kokura
Kokura
is an ancient castle town and the center of Kitakyūshū, Japan, guarding, via its suburb Moji, the Straits of Shimonoseki between Honshū and Kyūshū. Kokura is also the name of the penultimate station on the southbound Sanyo Shinkansen line, which is owned by JR Kyūshū and an important part of the...

, Hiroshima
Hiroshima
is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshu, the largest island of Japan. It became best known as the first city in history to be destroyed by a nuclear weapon when the United States Army Air Forces dropped an atomic bomb on it at 8:15 A.M...

, Niigata and Kyoto
Kyoto
is a city in the central part of the island of Honshū, Japan. It has a population close to 1.5 million. Formerly the imperial capital of Japan, it is now the capital of Kyoto Prefecture, as well as a major part of the Osaka-Kobe-Kyoto metropolitan area.-History:...

. At this point, Secretary of War Henry L. Stimson
Henry L. Stimson
Henry Lewis Stimson was an American statesman, lawyer and Republican Party politician and spokesman on foreign policy. He twice served as Secretary of War 1911–1913 under Republican William Howard Taft and 1940–1945, under Democrat Franklin D. Roosevelt. In the latter role he was a leading hawk...

 intervened, announcing that he would be making the targeting decision, and that he would not authorize the bombing of Kyoto on the grounds of its historical and religious significance. Groves therefore asked Arnold to remove Kyoto not just from the list of nuclear targets, but from targets for conventional bombing as well. One of Kyoto's substitutes was Nagasaki
Nagasaki
is the capital and the largest city of Nagasaki Prefecture on the island of Kyushu in Japan. Nagasaki was founded by the Portuguese in the second half of the 16th century on the site of a small fishing village, formerly part of Nishisonogi District...

.

Bombings


In May 1945, the Interim Committee
Interim Committee
The Interim Committee was a secret high-level group created in May 1945 by United States Secretary of War Henry L. Stimson at the urging of leaders of the Manhattan Project and with the approval of President Harry S. Truman to advise on matters pertaining to nuclear energy...

 was created to advise on wartime and postwar use of nuclear energy. The committee was chaired by Stimson, with James F. Byrnes
James F. Byrnes
James Francis Byrnes was an American statesman from the state of South Carolina. During his career, Byrnes served as a member of the House of Representatives , as a Senator , as Justice of the Supreme Court , as Secretary of State , and as the 104th Governor of South Carolina...

, a former US Senator soon to be Secretary of State
United States Secretary of State
The United States Secretary of State is the head of the United States Department of State, concerned with foreign affairs. The Secretary is a member of the Cabinet and the highest-ranking cabinet secretary both in line of succession and order of precedence...

, as President Truman's personal representative; Ralph A. Bard, the Under Secretary of the Navy; William L. Clayton
William L. Clayton
William Lockhart "Will" Clayton was an American business leader and government official.-Early life and career:...

, the Assistant Secretary of State; Vannevar Bush; Karl T. Compton; James B. Conant; and George L. Harrison
George L. Harrison
George Leslie Harrison was an American banker, insurance executive and advisor to Secretary of War Henry L. Stimson during World War II....

, an assistant to Stimson and president of New York Life Insurance Company
New York Life Insurance Company
The New York Life Insurance Company is one of the largest mutual life-insurance companies in the United States, and one of the largest life insurers in the world, with about $287 billion in total assets under management, and more than $15 billion in surplus and AVR...

. The Interim Committee in turn established a scientific panel consisting of Arthur Compton, Fermi, Lawrence and Oppenheimer to advise it on scientific issues. In its presentation to the Interim Committee, the scientific panel offered its opinion not just on the likely physical effects of an atomic bomb, but on its probable military and political impact.

At the Potsdam Conference
Potsdam Conference
The Potsdam Conference was held at Cecilienhof, the home of Crown Prince Wilhelm Hohenzollern, in Potsdam, occupied Germany, from 16 July to 2 August 1945. Participants were the Soviet Union, the United Kingdom, and the United States...

 in Germany, Truman was told that the Trinity test had been successful. He told Joseph Stalin
Joseph Stalin
Joseph Vissarionovich Stalin was the Premier of the Soviet Union from 6 May 1941 to 5 March 1953. He was among the Bolshevik revolutionaries who brought about the October Revolution and had held the position of first General Secretary of the Communist Party of the Soviet Union's Central Committee...

, the leader of the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

, that the US had a new superweapon, without giving any details. This was the first communication to the Soviet Union about the bomb, but Stalin already knew about it from spies. With the authorization to use the bomb against Japan already given, no alternatives were considered after the Japanese rejection of the Potsdam Declaration
Potsdam Declaration
The Potsdam Declaration or the Proclamation Defining Terms for Japanese Surrender is a statement calling for the Surrender of Japan in World War II. On July 26, 1945, United States President Harry S...

.
On 6 August 1945, the 393d Bombardment Squadron B-29 Enola Gay
Enola Gay
Enola Gay is a Boeing B-29 Superfortress bomber, named after Enola Gay Tibbets, mother of the pilot, then-Colonel Paul Tibbets. On August 6, 1945, during the final stages of World War II, it became the first aircraft to drop an atomic bomb as a weapon of war...

, piloted and commanded by Tibbets, lifted off with Parsons on board as weaponeer, and Little Boy in its bomb bay. Hiroshima, an important army depot and port of embarkation, was the primary target of the mission, with Kokura and Nagasaki as alternatives. With Farrell's permission, Parsons completed the bomb assembly in the air to minimize the risks during takeoff. The bomb detonated at an altitude of 1750 feet (533.4 m) with a blast that was later estimated to be the equivalent of 13 kilotons of TNT. An area of approximately 4.7 square miles (12.2 km²) was destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6–7% damaged. About 70,000 to 80,000 people, or some 30% of the population of Hiroshima, were killed immediately, and another 70,000 injured.

On the morning of 9 August 1945, the B-29 Bockscar
Bockscar
Bockscar, sometimes called Bock's Car or Bocks Car, is the name of the United States Army Air Forces B-29 bomber that dropped the "Fat Man" nuclear weapon over Nagasaki on 9 August 1945, the second atomic weapon used against Japan....

, piloted by the 393d Bombardment Squadron's commander, Major Charles W. Sweeney, lifted off with a Fat Man on board. This time, Ashworth served as weaponeer and Kokura
Kokura
is an ancient castle town and the center of Kitakyūshū, Japan, guarding, via its suburb Moji, the Straits of Shimonoseki between Honshū and Kyūshū. Kokura is also the name of the penultimate station on the southbound Sanyo Shinkansen line, which is owned by JR Kyūshū and an important part of the...

 was the primary target. Sweeney took off with the weapon already armed but with the electrical safety plugs still engaged. When they reached Kokura, they found cloud cover had obscured the city, prohibiting the visual attack required by orders. After three runs over the city, and with fuel running low, they headed for the secondary target, Nagasaki. Ashworth decided that a radar approach would be used if the target was obscured, but a last-minute break in the clouds over Nagasaki allowed a visual approach as ordered. The Fat Man was dropped over the city's industrial valley midway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works in the north. The resulting explosion had a blast yield equivalent to 21 kilotons of TNT, roughly the same as the Trinity blast, but was confined to the Urakami Valley
Urakami
Urakami was an area in the northern part of the city of Nagasaki. It is the exact ground zero where the atomic bomb exploded on August 9, 1945. It is the site of Urakami Cathedral, which was the largest cathedral in East Asia before it was destroyed by the bomb and then rebuilt.-External links:...

, and a major portion of the city was protected by the intervening hills. About 44% of the city was destroyed; 35,000 people were killed and 60,000 injured.

Groves expected to have another atomic bomb ready for use on 19 August, with three more in September and a further three in October. Two more Fat Man assemblies were readied. The third core
Demon core
The Demon core was the nickname given to a subcritical mass of plutonium that accidentally went briefly critical in two separate accidents at the Los Alamos laboratory in 1945 and 1946. Each incident resulted in the acute radiation poisoning and subsequent death of a scientist...

 was scheduled to leave Kirtland Field for Tinian on 12 August. Robert Bacher was packaging it at the Ice House at Los Alamos when he received word. However, when the Japanese initiated surrender negotiations
Surrender of Japan
The surrender of Japan in 1945 brought hostilities of World War II to a close. By the end of July 1945, the Imperial Japanese Navy was incapable of conducting operations and an Allied invasion of Japan was imminent...

, Groves ordered the shipments suspended. On 11 August, Groves phoned Warren with orders to organize a survey team to report on the damage and radioactivity at Hiroshima and Nagasaki. A party equipped with portable geiger counter
Geiger counter
A Geiger counter, also called a Geiger–Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a...

s arrived in Hiroshima on 8 September headed by Farrell and Warren, with Japanese Rear Admiral Masao Tsuzuki, who acted as a translator. They remained in Hiroshima until 14 September and then surveyed Nagasaki from 19 September to 8 October. This and other scientific missions to Japan would provide valuable scientific and historical data.

The necessity of the bombings of Hiroshima and Nagasaki became a subject of controversy among historians. Some questioned whether an "atomic diplomacy" would not have attained the same goals and disputed whether the bombings or the Soviet declaration of war on Japan was decisive. David H. Frisch
David H. Frisch
David H. Frisch was an American physicist who helped develop the atom bomb in World War II and later became active in the disarmament movement....

 recounts that alternative proposals such as a technical demonstration of an atomic explosion to the Japanese were circulated among scientists but in the end were not carefully analyzed. The Franck Report
Franck Report
The Franck Report of June 1945 was a document signed by several prominent nuclear physicists recommending that the United States not use the atomic bomb as a weapon to prompt the surrender of Japan in World War II....

 was the most notable effort pushing for a demonstration but was turned down by the Interim Committee's scientific panel.

After the war


During the war the words "Manhattan Project" gave any request for workers or rationed materials the highest priority. A 1945 account estimated, however, that "[p]robably no more than a few dozen men in the entire country knew the full meaning of the Manhattan Project, and perhaps only a thousand others even were aware that work on atoms was involved." The more than 100,000 others employed with the project "worked like moles in the dark". Warned that disclosing the project's secrets was punishable by 10 years in prison or a $10,000 ($ today) fine, they saw enormous quantities of raw materials enter factories with nothing coming out, and monitored "dials and switches while behind thick concrete walls mysterious reactions took place" without knowing the purpose of their jobs. The result amazed them as much as the rest of the world; newspapers in Oak Ridge announcing the Hiroshima bomb sold for $1 ($ today).

In anticipation of the bombings, Groves had Henry DeWolf Smyth
Henry DeWolf Smyth
Henry DeWolf "Harry" Smyth was an American physicist, diplomat, and bureaucrat who played a number of key roles in the early development of nuclear energy. Educated at Princeton University and the University of Cambridge, he was a faculty member in Princeton's Department of Physics from 1924 to...

 prepare a history for public consumption. The Atomic Energy for Military Purposes
Smyth Report
The Smyth Report was the common name given to an administrative history written by physicist Henry DeWolf Smyth about the Allied World War II effort to develop the atomic bomb, the Manhattan Project...

, better known as the "Smyth Report", was released to the public on 12 August 1945. Groves and Nichols presented Army–Navy "E" Awards to key contractors, whose involvement had hitherto been secret. Over 20 awards of the Presidential Medal for Merit
Presidential Medal for Merit
The Medal for Merit was, during the period it was awarded, the highest civilian decoration of the United States, awarded by the President of the United States to civilians for "exceptionally meritorious conduct in the performance of outstanding services ... since the proclamation of an emergency by...

 were made to key contractors and scientists, including Bush and Oppenheimer. Military personnel received the Legion of Merit
Legion of Merit
The Legion of Merit is a military decoration of the United States armed forces that is awarded for exceptionally meritorious conduct in the performance of outstanding services and achievements...

, including the commander of the Women's Army Corps
Women's Army Corps
The Women's Army Corps was the women's branch of the US Army. It was created as an auxiliary unit, the Women's Army Auxiliary Corps on 15 May 1942 by Public Law 554, and converted to full status as the WAC in 1943...

 detachment, Captain Arlene G. Scheidenhelm.

At Hanford, plutonium production fell off as Reactors B, D and F wore out, "poisoned" by fission products and swelling of the graphite moderator known as the Wigner effect
Wigner effect
The Wigner effect , also known as the discomposition effect, is the displacement of atoms in a solid caused by neutron radiation....

. The swelling damaged the charging tubes where the uranium was irradiated to produce plutonium, rendering them unusable. In order to maintain the supply of polonium for the urchin initiators, production was curtailed and the oldest unit, B pile, was closed down so at least one reactor would be available in the future. Research continued, with DuPont and the Metallurgical Laboratory developing a redox
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

 solvent extraction process as an alternative plutonium extraction
Nuclear reprocessing
Nuclear reprocessing technology was developed to chemically separate and recover fissionable plutonium from irradiated nuclear fuel. Reprocessing serves multiple purposes, whose relative importance has changed over time. Originally reprocessing was used solely to extract plutonium for producing...

 technique to the bismuth phosphate process
Bismuth phosphate process
Bismuth-phosphate process was a process used to extract plutonium from used nuclear fuel taken from nuclear reactors. This process was used to produce all the plutonium of the atomic bomb dropped on Nagasaki in 1945. In 1952 this process was replaced by the Redox and PUREX processes.-References:*...

, which left unspent uranium in a state from which it could not easily be recovered.

Bomb engineering was carried out by the Z Division, named for its director, Dr. Jerrold R. Zacharias
Jerrold R. Zacharias
Jerrold Reinach Zacharias was an American physicist and Institute Professor at the Massachusetts Institute of Technology.-Career:Zacharias was involved in both the Radiation Laboratory at MIT and the Manhattan Project...

 from Los Alamos. Z Division was initially located at Wendover Field but moved to Oxnard Field
Oxnard Field
Oxnard Field was the first airport in Albuquerque, New Mexico. It served as the home of commercial aviation in Albuquerque from 1928 to 1929 and remained in use for other purposes until 1948...

, New Mexico, in September 1945 to be closer to Los Alamos. This marked the beginning of Sandia Base
Sandia Base
Sandia Base was, from 1946 to 1971, the principal nuclear weapons installation of the United States Department of Defense. It was located on the southeastern edge of Albuquerque, New Mexico...

. Nearby Kirtland Field was used as a B-29 base for aircraft compatibility and drop tests. By October, all the staff and facilities at Wendover had been transferred to Sandia. As reservist officers were demobilized, they were replaced by about fifty hand-picked regular officers.

Nichols recommended that S-50 and the Alpha tracks at Y-12 be closed down. This was done in September. Although performing better than ever, the Alpha tracks could not compete with K-25 and the new K-27, which had commenced operation in January 1946. In December, the Y-12 plant was closed, thereby cutting the Tennessee Eastman payroll from 8,600 to 1,500 and saving $2 million a month.


Nowhere was demobilization more of a problem than at Los Alamos, where there was an exodus of talent. Much remained to be done. The bombs used on Hiroshima and Nagasaki were like laboratory pieces; work would be required to make them simpler, safer and more reliable. Implosion methods needed to be developed for uranium in place of the wasteful gun method, and composite uranium-plutonium cores were needed now that plutonium was in short supply because of the problems with the reactors. However, uncertainty about the future of the laboratory made it hard to induce people to stay. Oppenheimer returned to his job at the University of California and Groves appointed Norris Bradbury as an interim replacement. In fact, Bradbury world remain in the post for the next 25 years. Groves attempted to combat the dissatisfaction caused by the lack of amenities with a construction program that included an improved water supply, three hundred houses, and recreation facilities.

Two Fat Man–type detonations were conducted at Bikini Atoll
Bikini Atoll
Bikini Atoll is an atoll, listed as a World Heritage Site, in the Micronesian Islands of the Pacific Ocean, part of Republic of the Marshall Islands....

 in July 1946 as part of Operation Crossroads
Operation Crossroads
Operation Crossroads was a series of nuclear weapon tests conducted by the United States at Bikini Atoll in mid-1946. It was the first test of a nuclear weapon after the Trinity nuclear test in July 1945...

 to investigate the effect of nuclear weapons on warships. Able was detonated on 1 July 1946. The more spectacular Baker was detonated underwater on 25 July 1946.

In the face of the destructiveness of the new weapons and in anticipation of the nuclear arms race
Nuclear arms race
The nuclear arms race was a competition for supremacy in nuclear warfare between the United States, the Soviet Union, and their respective allies during the Cold War...

 several project members including Bohr, Bush and Conant expressed the view that it was necessary to reach agreement on international control of nuclear research and atomic weapons. The Baruch Plan
Baruch Plan
The Baruch Plan was a proposal by the United States government, written largely by Bernard Baruch but based on the Acheson–Lilienthal Report, to the United Nations Atomic Energy Commission in its first meeting in June 1946...

, unveiled in a speech to the newly formed United Nations Atomic Energy Commission
United Nations Atomic Energy Commission
The United Nations Atomic Energy Commission was founded on 24 January 1946 by Resolution 1 of the United Nations General Assembly "to deal with the problems raised by the discovery of atomic energy."...

 (UNAEC) in June 1946, proposed the establishment of an international atomic development authority, but was not adopted. Following a domestic debate over the permanent management of the nuclear program, the United States Atomic Energy Commission
United States Atomic Energy Commission
The United States Atomic Energy Commission was an agency of the United States government established after World War II by Congress to foster and control the peace time development of atomic science and technology. President Harry S...

 (AEC) was created by the Atomic Energy Act of 1946
Atomic Energy Act of 1946
The Atomic Energy Act of 1946 determined how the United States federal government would control and manage the nuclear technology it had jointly developed with its wartime allies...

 to take over the functions and assets of the Manhattan Project. It established civilian control over atomic development, and separated the development, production and control of atomic weapons from the military. Military aspects were taken over by the Armed Forces Special Weapons Project
Armed Forces Special Weapons Project
The Armed Forces Special Weapons Project was a United States military agency responsible for those aspects of nuclear weapons remaining under the military after the the Manhattan Project was succeeded by the Atomic Energy Commission on 1 January 1947...

 (AFSWP). Although the Manhattan Project ceased to exist on 31 December 1946, the Manhattan District would remain until it too was abolished on 15 August 1947.

Cost

style="margin-bottom: 5px;" | Manhattan Project costs through 31 December 1945
Site Cost (1945 USD) Cost (20 USD)
Oak Ridge $1,188,352,000 $
Hanford $390,124,000 $
Special operating materials $103,369,000 $
Los Alamos $74,055,000 $
Research and development $69,681,000 $
Government overhead $37,255,000 $
Heavy water plants $26,768,000 $
Total $1,889,604,000 $

The project expenditure through 1 October 1945 was $1.845 billion, and was $2.191 billion when the AEC assumed control on 1 January 1947. Total allocation was $2.4 billion. Over 90% of the cost was for building plants and producing the fissionable materials, and less than 10% for development and production of the weapons.

A total of four weapons (the Trinity gadget, Little Boy, Fat Man, and an unused bomb) were produced by the end of 1945, making the average cost per bomb around $500 million in 1945 dollars. By comparison, the project's total cost by the end of 1945 was about 90% of the total spent on the production of US small arms (not including ammunition) and 34% of the total spent on US tanks during the same period.

Legacy


The political and cultural impacts of the development of nuclear weapons were profound and far-reaching. The phrase "Atomic Age
Atomic Age
The Atomic Age, also known as the Atomic Era, is a phrase typically used to delineate the period of history following the detonation of the first nuclear bomb Trinity on July 16, 1945...

" was coined by William L. Laurence
William L. Laurence
William Leonard Laurence was a Jewish Lithuanian born American journalist known for his science journalism writing of the 1940s and 1950s while working for the New York Times...

, a New York Times journalist who became the official correspondent for the Manhattan Project. He witnessed both the Trinity test and the bombing of Nagasaki, and went on to write a series of articles extolling the virtues of the new weapon. His reporting before and after the bombings helped to spur public awareness of the potential of nuclear technology and motivated its development in the United States and the Soviet Union.

The wartime Manhattan Project left a legacy in the form of the network of national laboratories
United States Department of Energy National Laboratories
The United States Department of Energy National Laboratories and Technology Centers are a system of facilities and laboratories overseen by the United States Department of Energy for the purpose of advancing science and helping promote the economic and defensive national interests of the United...

: the Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory
The Lawrence Berkeley National Laboratory , is a U.S. Department of Energy national laboratory conducting unclassified scientific research. It is located on the grounds of the University of California, Berkeley, in the Berkeley Hills above the central campus...

, Los Alamos National Laboratory
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...

, Oak Ridge National Laboratory
Oak Ridge National Laboratory
Oak Ridge National Laboratory is a multiprogram science and technology national laboratory managed for the United States Department of Energy by UT-Battelle. ORNL is the DOE's largest science and energy laboratory. ORNL is located in Oak Ridge, Tennessee, near Knoxville...

, Argonne National Laboratory
Argonne National Laboratory
Argonne National Laboratory is the first science and engineering research national laboratory in the United States, receiving this designation on July 1, 1946. It is the largest national laboratory by size and scope in the Midwest...

 and Ames Laboratory
Ames Laboratory
Ames Laboratory is a United States Department of Energy national laboratory located in Ames, Iowa. The Laboratory conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup...

. Two more were established by Groves soon after the war, the Brookhaven National Laboratory
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...

 at Upton, New York
Upton, New York
Upton, New York is a hamlet on Long Island in the town of Brookhaven. It is the home of Brookhaven National Laboratory, and a National Weather Service station.Upton is located in Suffolk County, New York in the USA....

, and the Sandia National Laboratories
Sandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....

 at Albuquerque, New Mexico. Groves allocated $72 million to them for research activities in fiscal year 1946–1947. They would be in the vanguard of the kind of large-scale research that Alvin Weinberg, the director of the Oak Ridge National Laboratory, would call Big Science
Big Science
Big Science is a term used by scientists and historians of science to describe a series of changes in science which occurred in industrial nations during and after World War II, as scientific progress increasingly came to rely on large-scale projects usually funded by national governments or groups...

.

The Naval Research Laboratory had long been interested in the prospect of using nuclear power for warship propulsion, and sought to create its own nuclear project. In May 1946, Nimitz, now Chief of Naval Operations
Chief of Naval Operations
The Chief of Naval Operations is a statutory office held by a four-star admiral in the United States Navy, and is the most senior uniformed officer assigned to serve in the Department of the Navy. The office is a military adviser and deputy to the Secretary of the Navy...

, decided that the Navy should instead work with the Manhattan Project. A group of naval officers were assigned to Oak Ridge, the most senior of whom was Captain Hyman G. Rickover
Hyman G. Rickover
Hyman George Rickover was a four-star admiral of the United States Navy who directed the original development of naval nuclear propulsion and controlled its operations for three decades as director of Naval Reactors...

, who became assistant director there. They immersed themselves in the study of nuclear energy, laying the foundations for a nuclear-powered navy
Nuclear navy
Nuclear navy, or nuclear powered navy consists of ships powered by relatively small onboard nuclear reactors known as naval reactors. The concept was revolutionary for naval warfare when first proposed, as it meant that these vessels did not need to stop for fuel like their conventional...

. A similar group of Air Force personnel arrived at Oak Ridge in September 1946 with the aim of developing nuclear aircraft
Nuclear aircraft
A nuclear aircraft is an aircraft powered by nuclear energy. Research into them was pursued during the Cold War by the United States and the Soviet Union as they would presumably allow a country to keep nuclear bombers in the air for extremely long periods of time, a useful tactic for nuclear...

. Their Nuclear Energy for the Propulsion of Aircraft
Aircraft Nuclear Propulsion
The Aircraft Nuclear Propulsion program and the preceding Nuclear Energy for the Propulsion of Aircraft project worked to develop a nuclear propulsion system for aircraft. The United States Army Air Force initiated Project NEPA on May 28, 1946...

 (NEPA) project ran into formidable technical difficulties, and was ultimately cancelled.

The ability of the new reactors to create radioactive isotopes in previously unheard-of quantities sparked a revolution in nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...

 in the immediate postwar years. Starting in mid-1946, Oak Ridge began distributing radioisotopes to hospitals and universities. Most of the orders were for iodine-131
Iodine-131
Iodine-131 , also called radioiodine , is an important radioisotope of iodine. It has a radioactive decay half-life of about eight days. Its uses are mostly medical and pharmaceutical...

 and phosphorus-32
Phosphorus-32
Phosphorus-32 is a radioactive isotope of phosphorus. The nucleus of phosphorus-32 contains 15 protons and 17 neutrons, one more neutron than the most common isotope of phosphorus, phosphorus-31...

, which were used in the diagnosis and treatment of cancer. In addition to medicine, isotopes were also used in biological, industrial and agricultural research.

On handing over control to the Atomic Energy Commission, Groves bid farewell to the people who had worked on the Manhattan Project:

External links