Operation Castle

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Operation Castle

Operation Castle was a United States

United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
series of high-energy (high-yield

Nuclear weapon yield

The explosive yield of a nuclear weapon is the amount of energy, called the yield, discharged when a nuclear weapon is detonated, expressed usually in the equivalent mass of trinitrotoluene , either in kilotons or megatons , but sometimes also in terajoules ....
) nuclear tests by Joint Task Force SEVEN (JTF-7) at Bikini Atoll

Bikini Atoll

Bikini Atoll is an atoll in one of the Micronesian Islands in the Pacific Ocean, part of Marshall Islands. It consists of 36 islands surrounding a lagoon....
beginning in March 1954. It followed Operation Upshot-Knothole

Operation Upshot-Knothole

File:Operation Upshot test 2.oggOperation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site....
and preceded Operation Teapot

Operation Teapot

File:Operation Teapot test.oggOperation Teapot was a series of fourteen nuclear test explosions conducted at the Nevada Test Site in the first half of 1955....
.

Conducted as a joint venture between the 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 United States Congress to foster and control the peace time development of atomic science and technology....
(AEC) and the Department of Defense

United States Department of Defense

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Encyclopedia

Operation Castle was a United States

United States

Nuclear weapon yield

Bikini Atoll

Operation Upshot-Knothole

File:Operation Upshot test 2.oggOperation Upshot-Knothole was a series of eleven nuclear test shots conducted in 1953 at the Nevada Test Site....
and preceded Operation Teapot

Operation Teapot

United States Atomic Energy Commission

United States Department of Defense

The United States Department of Defense is the federal department charged with coordinating and supervising all agencies and functions of the government relating directly to national security and the Military of the United States....
(DoD), the ultimate objective of the operation was to test designs for an aircraft-deliverable thermonuclear weapon.

Operation Castle was considered by government officials to be a success as it proved the feasibility of deployable "dry fuel" designs for thermonuclear weapons. There were, however, technical difficulties with some of the tests: one device had a yield much lower than its predicted yield (a "fizzle"), while two other devices detonated with over twice their predicted yields. One test in particular, Castle Bravo

Castle Bravo

Castle Bravo was the code name given to the first U.S. test of a so-called dry fuel Nuclear fusion hydrogen bomb device, detonated on March 1, 1954, at Bikini Atoll, Marshall Islands, by the United States, as the first test of Operation Castle ....
, resulted in extensive radiological contamination of nearby islands (including inhabitants and U.S. soldiers stationed there), as well as a nearby Japanese fishing boat (Daigo Fukuryu Maru
Daigo Fukuryu Maru

was a Japanese tuna fishing boat, which was exposed to and contaminated by nuclear fallout from the United States' Castle Bravo thermonuclear device test on Bikini Atoll, on March 1, 1954....
), resulting in one direct fatality and continued health problems for many of those exposed. Public reaction to the tests and an awareness of the long-range effects of nuclear fallout

Nuclear fallout

Fallout is the residual radiation hazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion....
has been attributed as being part of the motivation for the Partial Test Ban Treaty

Partial Test Ban Treaty

The Treaty banning Nuclear Weapon Tests In The Atmosphere, In Outer Space And Under Water, often abbreviated as the Partial Test Ban Treaty , Limited Test Ban Treaty , or Nuclear Test Ban Treaty is a treaty prohibiting all nuclear testing of nuclear weapons Underground nuclear testing....
of 1963.

Background

Bikini Atoll

Bikini Atoll is an atoll in one of the Micronesian Islands in the Pacific Ocean, part of Marshall Islands. It consists of 36 islands surrounding a lagoon....
had previously hosted nuclear testing in 1946 as part of Operation Crossroads

Operation Crossroads

Operation Crossroads was a series of nuclear weapon tests conducted by the United States and nuclear weapons at Bikini Atoll in the summer of 1946....
where the world’s fourth and fifth atomic weapons were detonated in Bikini Lagoon. Since then, US nuclear weapons testing had moved to Eniwetok Atoll

Enewetak

File:Enewetak or Eniwetok atoll.jpgEnewetak is an atoll in the Marshall Islands of the central Pacific Ocean. Its land consists of about 40 small islets totaling less than 6 km?, surrounding a lagoon, 80 km in circumference....
to take advantage of generally larger islands and deeper water. Both Atolls were part of the US Pacific Proving Grounds

Pacific Proving Grounds

The Pacific Proving Grounds was the name used to describe a number of sites in the Marshall Islands and a few other sites in the Pacific Ocean, used by the United States to conduct nuclear testing at various times between 1946 and 1962....
.

However, the extremely high yields of the Castle weapons caused concern within the AEC that potential damage to the limited infrastructure already established at Eniwetok would delay other operations. Additionally, the cratering from the Castle weapons was expected to be comparable to that of Ivy Mike

Ivy Mike

Ivy Mike was the codename given to the first US test of a nuclear fusion device where a major part of the explosive yield came from fusion. It was detonated on November 1, 1952 by the United States at on Enewetak, an atoll in the Pacific Ocean, as part of Operation Ivy....
, a 10.4 Mt device tested at Eniwetok in 1952 leaving a crater approximately 1 mile (1.6 km) in diameter.Operation Ivy, pg 192

The Ivy Mike test had been the world’s first full scale thermonuclear or fusion

Nuclear fusion

In nuclear physics and nuclear chemistry, nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus....
explosion. The Mike device used liquid deuterium

Deuterium

Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen ....
, an isotope

Isotope

Isotopes are any of the different types of atoms of the same chemical element, each having a different atomic mass . Isotopes of an element have atomic nucleus with the same number of protons but different numbers of neutron....
of hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the chemical symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly combustion and explosive Diatomic molecule gas with the molecular formula H2....
, making it a "wet bomb." The complex dewar mechanisms needed to store the liquid deuterium at cryogenic temperatures made the device three stories tall and 82 tons in total weight, far from being a deliverable weapon. With the success of Ivy Mike as a proof of the Teller-Ulam concept, research began on using a “dry" fuel to make a practical fusion weapon so that the United States could begin deploying thermonuclear designs in quantity. This applied the Teller-Ulam concept with lithium deuteride as the fusion fuel, greatly reducing size, weight, and complexity. Operation Castle was chartered to test four dry fuel designs, two wet bombs, and one smaller device. Approval for Operation Castle was communicated to JTF-7 by Major General Kenneth D. Nichols, General Manager of the AEC, on 21 January, 1954.

Experiments

Operation Castle was organized into 7 experiments, all but one which were to take place at Bikini Atoll. Below is the original test schedule (as of February 1954).

Operation Castle Schedule
Experiment	Device	Prototype	Fuel	Date	Predicted Yield	Manufacturer	Test Location
BRAVO Castle Bravo Castle Bravo was the code name given to the first U.S. test of a so-called dry fuel Nuclear fusion hydrogen bomb device, detonated on March 1, 1954, at Bikini Atoll, Marshall Islands, by the United States, as the first test of Operation Castle ....	Shrimp	TX-21	40% Li-6 D (dry)	1 March, 1954	6 Mt	Los Alamos Scientific Laboratory	Reef off Nam Is, Bikini
UNION Castle Union Castle Union was the code name given to one of the tests in the Operation Castle series of USA Nuclear testing. It was the first test of the Mark 14 nuclear bomb thermonuclear weapon , one of the first deployed U.S....	Alarm Clock	EC-14	95% Li-6 D (dry)	11 March, 1954	3-4 Mt	Los Alamos Scientific Laboratory	Barge off Iroij, Bikini
YANKEE Castle Yankee Castle Yankee was the code name given to one of the tests in the Operation Castle series of American Nuclear testing....	Jughead	TX/EC-16	Cryo H-3 (wet)	22 March, 1954	8 Mt	Los Alamos Scientific Laboratory	Barge off Iroij, Bikini
ECHO	Ramrod	N/A	Cryo H-3 (wet)	29 March, 1954	65-275 Kt	University of California Radiation Laboratory (Livermore)	Eleleron, Enewetak
NECTAR	Zombie	TX-15	Boosted fission	5 April, 1954	1.8 Mt	Los Alamos Scientific Laboratory	Barge off Iroij, Bikini
ROMEO Castle Romeo Castle Romeo was the code name given to one of the tests in the Operation Castle series of American Nuclear testing. It was the first test of the TX-17 thermonuclear weapon , the first deployed U.S....	Runt	TX/EC-17A	7.5% Li-6 D (natural)	15 April, 1954	4 Mt	Los Alamos Scientific Laboratory	Barge off Iroij, Bikini
KOON Castle Koon The Koon shot of Operation Castle was a test of a University of California Radiation Laboratory designed nuclear weapon.The 'dry' two-stage device was known as "Morgenstern"....	Morgenstern	N/A	7.6% Li-6 D (natural)	22 April, 1954	1 Mt	University of California Radiation Laboratory (Livermore)	Eneman, Bikini

Operation Castle was intended to test lithium deuteride (LiD) as a thermonuclear fusion fuel. A solid at room temperature, "dry" LiD, if it worked, would be far more practical than the cryogenic liquid deuterium (hydrogen-2) fuel in the Ivy Mike device. The same Teller-Ulam principle would be used as in the Ivy Mike "Sausage" device, but the fusion reactions were different. Mike fused deuterium with deuterium, but the LiD devices would fuse deuterium with tritium. The tritium was produced during the explosion by irradiating the lithium with fast neutrons

Neutron temperature

The neutron temperature, also called the neutron energy, indicates a free neutron kinetic energy, usually given in electron volts. The term temperature is used, since hot, thermal and cold neutrons are Neutron moderator in a medium with a certain temperature....
.

Bravo and Union used lithium enriched in the Li-6 isotope while Romeo and Koon were fueled with natural lithium (92% Li-7, 7.5% Li-6). The use of natural lithium would be important to the ability of the US to rapidly expand its nuclear stockpile during the cold war 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....
.

As a hedge, development of liquid deuterium weapons continued in parallel. Even though they were much less practical because of the logistical problems dealing with the transport, handling, and storage of a cryogenic device, the cold war arms race drove the demand for a viable fusion weapon. The Ramrod and Jughead devices were liquid fuel designs greatly reduced in size and weight from their Ivy Mike "Sausage" predecessor. The Jughead device was ultimately weaponized and saw limited fielding in the inventory until the dry fuel weapons were common.

Nectar was not a fusion weapon in the same sense as the rest of the Castle series. Even though it used a dry lithium fuel for fission boosting, the principal reaction material in the second stage was uranium and plutonium. Similar to the Teller-Ulam configuration, a fission

Nuclear fission

In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the atomic nucleus of an atom splits into smaller parts, often producing free neutrons and lighter atomic nucleus, which may eventually produce photons ....
device was used to create high temperatures and pressures in order to compress a second fissionable mass that would have otherwise been too large to sustain an efficient reaction if it were triggered with conventional explosives. This experiment was intended to develop intermediate yield weapons for expanding the inventory (around 1-2 Mt vs. 4-8).

It should be noted that many "fusion" or "thermonuclear" weapons still generate much or even most of their yields from fission. Although the U-238 isotope of uranium (i.e., "natural" or "depleted" uranium) will not sustain a chain reaction, it still fissions when irradiated by the intense fast neutron flux of a fusion explosion. Because U-238 is plentiful and has no critical mass, it can be added in almost unlimited quantities as a "tamper" around a fusion bomb, helping to contain the fusion reaction and contributing its own fission energy. Fission of the U-238 tamper contributed 77% -- 8 megatons -- to the yield of the 10.4 Mt Ivy Mike explosion.

Test execution

The most notable event of Operation Castle was the Bravo test. The dry fuel for Bravo was 40% Li-6 and 60% Li-7. Only Li-6 was expected to breed tritium for the deuterium-tritium fusion reaction; Li-7 was expected to be inert. Yet J. Carson Mark

J. Carson Mark

J. Carson Mark was a Canadian-born United States mathematician known especially for his work on developing nuclear weapons for the United States at Los Alamos National Laboratory....
, head of the Los Alamos Theoretical Design Division, had speculated that Bravo could "go big", estimating that the device could produce an explosive yield as much as 20% more than had been originally calculated. Li-7 turned out to be an excellent source of tritium through a previously unquantified reaction. Bravo exceeded expectations by 250%, yielding

Nuclear weapon yield

The explosive yield of a nuclear weapon is the amount of energy, called the yield, discharged when a nuclear weapon is detonated, expressed usually in the equivalent mass of trinitrotoluene , either in kilotons or megatons , but sometimes also in terajoules ....
15 Mt -- 1,000 times more powerful than the Little Boy

Little Boy

Little Boy was the codename of the atomic bomb that was dropped on Hiroshima, Japan, on August 6, 1945 by the B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets in the 393d Bomb Squadron of the United States Army Air Forces....
weapon used on Hiroshima

Hiroshima

The Japanese city of is the capital of Hiroshima Prefecture, and the largest city in the Chugoku region of western Honshu, the largest of Japan's islands....
. Bravo is to this day the largest detonation ever conducted by the United States, and the seventh largest ever detonated in the world.

Because Bravo greatly exceeded its expected yield, JTF-7 was caught unprepared. Much of the permanent infrastructure on Bikini Atoll

Bikini Atoll

Bikini Atoll is an atoll in one of the Micronesian Islands in the Pacific Ocean, part of Marshall Islands. It consists of 36 islands surrounding a lagoon....
was heavily damaged. The intense thermal flash ignited a fire at a distance of on the island of Eneu (base island of Bikini Atoll). The ensuing fallout

Nuclear fallout

Fallout is the residual radiation hazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion....
contaminated all of the atoll, so much so that it could not be approached by JTF-7 for 24 hours after the test, and even then exposure times were limited. As the fallout spread downwind to the east, more atolls were contaminated with activated calcium ash. Although the atolls were evacuated soon after the test, 239 Marshallese on the Utirik

Utirik Atoll

Utirik Atoll is an atoll of 10 islands in the Pacific Ocean. It is a legislative district of the Ratak Chain of the Marshall Islands. Its total land area is only 0.94 miles?, but that encloses a lagoon of 22.29 miles?....
, Rongelap

Rongelap Atoll

Rongelap Atoll is an island-atoll located in Micronesia. It is a municipality of the Marshall Islands. The Atoll consists of 61 islets with a combined area of approximately 3 square miles ....
, and Ailinginae Atoll

Ailinginae Atoll

Ailinginae Atoll is an atoll of 25 islands in the Pacific Ocean. It is a legislative district of the Ralik Chain of the Marshall Islands. Its total land area is only 1.08 miles?, but that encloses a lagoon of 40.91 miles?....
s were subjected to significant levels of radiation. 28 Americans stationed on the Rongerik Atoll were also exposed. Follow-up studies of the contaminated individuals began soon after the blast as Project 4.1

Project 4.1

Project 4.1 was the designation for a medical study conducted by the United States of those residents of the Marshall Islands exposed to nuclear fallout from the March 1, 1954 Castle Bravo nuclear testing at Bikini Atoll, which had an unexpectedly large nuclear weapons yield....
, and though the short-term effects of the radiation exposure for most of the Marshallese were mild and/or hard to correlate, the long-term effects were pronounced. Additionally, 23 Japanese fishermen aboard Lucky Dragon No. 5
Daigo Fukuryu Maru

was a Japanese tuna fishing boat, which was exposed to and contaminated by nuclear fallout from the United States' Castle Bravo thermonuclear device test on Bikini Atoll, on March 1, 1954....
were also exposed to high levels of radiation. They suffered symptoms of radiation poisoning

Radiation poisoning

Radiation poisoning, also called "radiation sickness" or a "creeping dose", is a form of damage to organ tissue due to excessive exposure to ionizing radiation....
, and one crew member died in September 1954.

The heavy contamination and extensive damage from Bravo significantly delayed the rest of the series. The post-Bravo schedule was revised on 14 April, 1954.

Operation Castle Schedule (Post BRAVO)
Experiment	Original Date	Revised Date	Original Yield	Revised Yield
UNION Castle Union Castle Union was the code name given to one of the tests in the Operation Castle series of USA Nuclear testing. It was the first test of the Mark 14 nuclear bomb thermonuclear weapon , one of the first deployed U.S....	11 March, 1954	22 April, 1954	3-4 Mt	5-10 Mt
YANKEE Castle Yankee Castle Yankee was the code name given to one of the tests in the Operation Castle series of American Nuclear testing....	22 March, 1954	27 April, 1954	8 Mt	9.5 Mt
NECTAR	5 April, 1954	20 April	1.8 Mt	1-3 Mt
ROMEO Castle Romeo Castle Romeo was the code name given to one of the tests in the Operation Castle series of American Nuclear testing. It was the first test of the TX-17 thermonuclear weapon , the first deployed U.S....	15 April, 1954	27 March, 1954	4 Mt	8 Mt
KOON Castle Koon The Koon shot of Operation Castle was a test of a University of California Radiation Laboratory designed nuclear weapon.The 'dry' two-stage device was known as "Morgenstern"....	22 April, 1954	7 April, 1954	1 Mt	1.5 Mt

The Romeo and Koon tests were complete by the time of this revision. The Echo test was canceled due to the liquid fuel design becoming obsolete with the success of the dry-fueled Bravo. Yankee was similarly considered obsolete and the Yankee test was conducted using a Runt II device (similar to the Union device) hastily completed at Los Alamos and flown to Bikini. With this revision, both of the "wet" fuel devices were removed from the test schedule.

As Operation Castle continued, the increased yields and fallout caused test locations to be re-evaluated. While the majority of the tests were planned for barges near the sand spit of Iroij, some were moved to the Bravo and Union craters. Additionally, Nectar was moved from Bikini Atoll to the Ivy Mike crater at Enewetak

Enewetak

File:Enewetak or Eniwetok atoll.jpgEnewetak is an atoll in the Marshall Islands of the central Pacific Ocean. Its land consists of about 40 small islets totaling less than 6 km?, surrounding a lagoon, 80 km in circumference....
for expediency since Bikini was still heavily contaminated from the previous tests.

The final test in Operation Castle took place on 14 May, 1954.

Operation Castle (Actual)
Experiment	Date	Yield	Location
BRAVO Castle Bravo Castle Bravo was the code name given to the first U.S. test of a so-called dry fuel Nuclear fusion hydrogen bomb device, detonated on March 1, 1954, at Bikini Atoll, Marshall Islands, by the United States, as the first test of Operation Castle ....	1 March, 1954	15Mt	Reef off Nam Is, Bikini
ROMEO Castle Romeo Castle Romeo was the code name given to one of the tests in the Operation Castle series of American Nuclear testing. It was the first test of the TX-17 thermonuclear weapon , the first deployed U.S....	27 March, 1954	11 Mt	Barge in BRAVO crater, Bikini
KOON Castle Koon The Koon shot of Operation Castle was a test of a University of California Radiation Laboratory designed nuclear weapon.The 'dry' two-stage device was known as "Morgenstern"....	7 April, 1954	110 kt	Eneman, Bikini
UNION Castle Union Castle Union was the code name given to one of the tests in the Operation Castle series of USA Nuclear testing. It was the first test of the Mark 14 nuclear bomb thermonuclear weapon , one of the first deployed U.S....	26 April, 1954	6.9 Mt	Barge off Iroij, Bikini
YANKEE Castle Yankee Castle Yankee was the code name given to one of the tests in the Operation Castle series of American Nuclear testing....	5 May, 1954	13.5 Mt	Barge in UNION, Bikini
NECTAR	14 May, 1954	1.69 Mt	Barge Ivy-MIKE crater, Enewetak

Results

Operation Castle was an unqualified success for the implementation of dry fuel devices. The Bravo design was quickly weaponized and is suspected to be the progenitor of the Mk-21

Mark 21 nuclear bomb

The Mark 21 nuclear bomb was a nuclear gravity bomb first produced in 1955, based on the results of Operation Castle. While most of the shots of the Castle series were intended to test weapons intended for immediate stockpile, or which were already available for use as part of the Emergency Capability program, the first shot, Castle Bravo wa...
gravity bomb. The Mk-21 design project began on 26 March, 1954 (just three weeks after Bravo) with production of 275 weapons beginning in the fall of 1955. Romeo, relying on natural lithium, was rapidly turned into the Mk-17 bomb

Mark 17 nuclear bomb

The Mark 17 and Mark 24 nuclear bomb were the first Mass production hydrogen bombs deployed by the United States. The two differed in their "primary" stages....
, the US first H bomb , and was available to strategic forces as an Emergency Capability by late summer of 1954. Most of the Castle dry fuel devices eventually appeared in the inventory and ultimately grandfathered the majority of thermonuclear configurations.

In contrast, the Livermore

Lawrence Livermore National Laboratory

The Lawrence Livermore National Laboratory in Livermore, California is a scientific research laboratory founded by the University of California in 1952....
-designed Koon design was a failure. Using natural lithium and a heavily modified Teller-Ulam configuration, the test produced only 110 Kt of an expected 1.5 Mt. While engineers at the Radiation Laboratory had hoped it would lead to a promising new field of weapons, it was eventually determined that the design allowed premature heating of the lithium fuel, thereby disrupting the delicate fusion conditions.

Operation Castle

Background

Experiments

Test execution

Results

See also

Bibliography

External links