Neptunium

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Neptunium

Neptunium is a chemical element

Chemical element

A chemical element is a type of atom that is distinguished by its atomic number; that is, by the number of protons in its atomic nucleus. The term is also used to refer to a pure chemical Chemical substance composed of atoms with the same number of protons....
with the symbol Np and atomic number

Atomic number

In chemistry and physics, the atomic number is the number of protons found in the atomic nucleus of an atom. It is conventionally represented by the symbol Z....
93. A radioactive metallic element, neptunium is the first transuranic element and belongs to the actinide

Actinide

According to IUPAC nomenclature, the actinoid series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103....
series. Its most stable 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....
, ²³⁷Np, is a by-product of nuclear reactor

Nuclear reactor

A nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate, as opposed to a nuclear bomb, in which the chain reaction occurs in a fraction of a second and is uncontrolled causing an explosion....
s and plutonium

Plutonium

Plutonium is a rare transuranic radioactive chemical element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when plutonium oxide....
production and it can be used as a component in neutron

Neutron

The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutrons are usually found in atomic nucleus....
detection equipment. Neptunium is also found in trace amounts in uranium

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
ores.

ery in appearance, neptunium metal

Metal

In chemistry, a metal is a chemical element whose atoms readily lose electrons to form positive ions , and form metallic bonds between other metal atoms and ionic bonds between nonmetal atoms....
is fairly chemically reactive

Chemical reaction

A chemical reaction is a process that always results in the interconversion of chemical substances. The substance or substances initially involved in a chemical reaction are called reactants....
and is found in at least three allotropes:

element has four ionic 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 Electrical charge that an atom would have if all bonds to atoms of different elements were 100% Ionic bond....
s while in solution:

Neptunium forms tri- and tetrahalide

Halide

A halide is a binary compound, of which one part is a halogen atom and the other part is an chemical element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, or astatide compound....
s such as NpF₃, NpF₄, NpCl₄, NpBr₃, NpI₃, and oxide

Oxide

An oxide is a chemical compound contaning at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides....
s of the various compositions such as are found in the uranium-oxygen

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
system, including Np₃O₈ and NpO₂.

NpF₅ is volatile like uranium hexafluoride

Uranium hexafluoride

Uranium hexafluoride , referred to as "hex" in the nuclear industry, is a compound used in the uranium Isotope separation#Centrifugal Force process that produces fuel for nuclear reactors and nuclear weapons....
.

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Encyclopedia

Neptunium is a chemical element

Chemical element

Atomic number

Actinide

Isotope

Nuclear reactor

Plutonium

Neutron

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
ores.

Characteristics

Silvery in appearance, neptunium metal

Metal

Chemical reaction

alpha-neptunium, orthorhombic, density 20.45 g/cm³
beta-neptunium (above 280 °C), tetragonal, density (313 °C) 19.36 g/cm³
gamma-neptunium (above 577 °C), cubic, density (600 °C) 18 g/cm³

Compounds

This element has four ionic oxidation state

Oxidation state

Np⁺³ (pale purple), analogous to the rare earth ion Pm⁺³
Np⁺⁴ (yellow green)
NpO₂⁺ (green blue)
NpO₂⁺⁺ (pale pink)

Neptunium forms tri- and tetrahalide

Halide

Oxide

Oxygen

Uranium hexafluoride

Fluoride volatility

Fluoride volatility is a method for the extraction of elements which form Volatility fluorides. It is being studied for nuclear reprocessing of nuclear fuel, either of the conventional fuel rods used in today's LWRs, or as an integral part of a molten salt reactor system....
and uranium enrichment.

Neptunium like other actinides readily forms a dioxide neptunyl core (NpO₂). In the environment, this neptunyl core readily complexes with carbonate as well as other oxygen moieties (OH^-, NO₂^-, NO₃^-, and SO₄^-2) to form charged complexes which tend to be readily mobile with low affinities to soil.

NpO₂(OH)₂^-1
NpO₂(CO₃)^-1
NpO₂(CO₃)₂^-3
NpO₂(CO₃)₃^-5

Uses

Precursor in Plutonium-238 Production

²³⁷Np is irradiated with neutrons to create ²³⁸Pu, a rare and valuable isotope for spacecraft and military applications. ²³⁷Np will capture a neutron to form ²³⁸Np and beta decay with a half life of two days to ²³⁸Pu.

Weapons applications

Neptunium is fissionable, and could theoretically be used as fuel in a fast neutron reactor

Fast neutron reactor

A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons....
or a nuclear weapon

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission or a combination of fission and nuclear fusion....
. In 1992, the U.S. Department of Energy declassified the statement that Np-237 "can be used for a nuclear explosive device". It is not believed that an actual weapon has ever been constructed using neptunium.

In September 2002, researchers at the University of California

University of California

The University of California is a public university system in the U.S. state of California. Under the California Master Plan for Higher Education, the University of California is a part of the state's three-tier public higher education system, which also includes the California State University system and the California Community Colleges s...
Los Alamos National Laboratory

Los Alamos National Laboratory

Los Alamos National Laboratory is a United States Department of Energy United States Department of Energy National Labs, managed and operated by Los Alamos National Security, LLC , located in Los Alamos, New Mexico....
created the first known nuclear critical mass

Critical Mass

Critical Mass is a bicycling event typically held on the last Friday of every month in over 300 city around the world. While the ride was originally founded in 1992 with the idea of drawing attention to how unfriendly the city was to bicyclists, the leaderless structure of Critical Mass makes it impossible to assign it any one specific goal...
using neptunium in combination with enriched uranium

Enriched uranium

Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation....
, discovering that the critical mass of neptunium is around 60 kg, showing that it "is about as good a bomb material as U-235

U-235

U235 or U-235 may be:* German submarine U-235, a German U-boat of World War II* Uranium-235, an isotope of uraniumbang bang there goes the ship...
." US officials in March 2004, planned to move the nation's supply of separated neptunium to a site in Nevada.

Other

Neptunium is also used in Neutron detection devices.

History

Neptunium (named for the planet Neptune, the next planet

Planet

A planet , as 2006 definition of planet by the International Astronomical Union , is a celestial body orbiting a star or Stellar evolution#Stellar remnants that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared the neighbourhood of planetesimals....
out from Uranus

Uranus

Uranus is the seventh planet from the Sun and the third-largest and fourth most massive planet in the Solar System. It is named after the ancient Greek deity of the sky Uranus the father of Kronos and grandfather of Zeus ....
, after which uranium

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
was named) was first discovered by 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 received the Nobel Prize in Chemistry in 1951....
and Philip H. Abelson in the year 1940 in Berkeley, California. Initially predicted by Walter Russell

Walter Russell

Walter Russell was an American polymath best known for his achievements in painting, sculpture, architecture, and for his controversial unified theory in physics and cosmogony....
's "spiral" organization of the periodic table, it was found at the Berkeley Radiation Laboratory of the University of California, Berkeley

University of California, Berkeley

The University of California, Berkeley is a public university research university located in Berkeley, California, California, United States. The oldest of the ten major campuses affiliated with the University of California, Berkeley offers some 300 undergraduate and graduate degree programs in a wide range of disciplines....
where the team produced the neptunium isotope

Isotope

Half-life

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
with slow moving neutrons. It was the first transuranium element

Transuranium element

In chemistry, transuranium elements are the chemical elements with atomic numbers greater than 92 . None of these elements are stable; they Radioactive decay into other elements....
produced synthetically and the first actinide series transuranium element discovered.

Occurrence

Trace amounts of neptunium are found naturally as decay product

Decay product

In nuclear physics, a decay product, also known as a daughter product, daughter isotope or daughter nuclide, is a nuclide resulting from the radioactive decay of a parent isotope or precursor nuclide....
s from transmutation reactions in uranium ores. Artificial ²³⁷Np is produced through the reduction

Redox

Redox describes all chemical reactions in which atoms have their oxidation number changed.This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
of ²³⁷NpF₃ with barium

Barium

Barium is a chemical element. It has the symbol Ba, and atomic number 56. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with Earth's atmosphere....
or lithium

Lithium

Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft alkali metal with a silver-white color. Under standard conditions for temperature and pressure, it is the lightest metal and the least dense solid element....
vapor at around 1200 °C

Celsius

Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death....
and is most often extracted from spent nuclear fuel rods as a by-product in plutonium

Plutonium

Spent nuclear fuel

File:Spent nuclear fuel hanford.jpgSpent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor to the point where it is no longer useful in sustaining a nuclear reaction....
discharges.

Nuclear synthesis

When an ²³⁵U
Uranium-235

Uranium-235 is an Isotopes of uranium that differs from the element's other common isotope, uranium-238, by its ability to cause a rapidly expanding nuclear fission chain reaction, i.e., it is fissile....
atom captures a neutron, it is converted to an excited state of ²³⁶U
Uranium-236

Uranium-236 is an Isotopes of uranium that is neither fissile with thermal neutrons, nor very good fertile material, but is generally considered a nuisance and long-lived radioactive waste....
. About 81 % of the excited ²³⁶U nuclei undergo fission, but the remainder decay to the ground state of ²³⁶U by emitting gamma radiation. Further neutron capture
Neutron capture

Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus....
creates ²³⁷U which has a half-life of 7 days and thus quickly decays to ²³⁷Np.

²³⁷U is also produced via an (n
Neutron

The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutrons are usually found in atomic nucleus....
,2n) reaction with ²³⁸U
Uranium-238

Uranium-238 , is the most common Isotopes of uranium of uranium found in nature. When hit by a neutron, it becomes uranium-239 , an unstable isotope which radioactive decay into neptunium-239 , which then itself decays, with a half-life of 2.355 days, into plutonium-239 ....
. This only happens with very energetic neutrons.

²³⁷Np is the product of alpha decay
Alpha decay

Alpha decay is a type of radioactivity decay in which an atomic nucleus emits an alpha particle and transforms into an atom with a mass number 4 less and atomic number 2 less....
of ²⁴¹Am.

Since nearly all neptunium is produced in this way or consists of heavier isotopes which decay quickly, one gets nearly pure ²³⁷Np by chemical separation of neptunium from spent nuclear fuel

Spent nuclear fuel

Role in nuclear waste

Neptunium-237 is the most mobile actinide

Actinide

Deep geological repository

A deep geological repository is a radioactive waste repository excavated below 300 m within a salt dome or bedrock. It entails a combination of waste form, waste package and engineered seals that is designed to provide a high level of long-term storage without future maintenance....
environment. This makes it and its predecessors such as americium-241 candidates of interest for destruction by nuclear transmutation. Neptunium accumulates in commercial household ionization-chamber smoke detectors from decay of the (typically) 0.2 microgram

Microgram

In the metric system, a microgram is 1/1,000,000 of a gram , or 1/1000 of a milligram, is one of the smallest units of weight/mass commonly used....
) of americium-241 initially present as a source of ionizing radiation

Ionizing radiation

Ionizing radiation consists of subatomic particle radiation or electromagnetic radiation that are energetic enough to detach electrons from atoms or molecules, ionize them....
. With a half-life of 432 years, the americium-241 in a smoke detector includes about 5 % neptunium after 22 years, and about 10 % after 43 years. After the 432-year americium-241 half-life, a smoke detector's original americium would be more than half neptunium.

Due to its long half life neptunium becomes the major contributor of the total radiation in 10000 years. As it is unclear what happens to the containment in that long time span a extraction of the neptunium would minimize the contamination of the environment if the nuclear waste could be mobilized after several thousand years.

Isotopes

19 neptunium radioisotopes have been characterized, with the most stable being ²³⁷Np with a half-life

Half-life

The half-life of a quantity whose value decreases with time is the interval required for the quantity to decay to half of its initial value. The concept originated in describing how long it takes atoms to undergo radioactive decay but also applies in a wide variety of other situations....
of 2.14 million years, ²³⁶Np with a half-life of 154,000 years, and ²³⁵Np with a half-life of 396.1 days. All of the remaining radioactive isotopes have half-lives that are less than 4.5 days, and the majority of these have half-lives that are less than 50 minutes. This element also has 4 meta states, with the most stable being ^236mNp (t_½ 22.5 hours).

The isotopes of neptunium range in atomic weight

Atomic weight

Atomic weight is a Dimensionless quantity physical quantity, the ratio of the average mass of atoms of an chemical element to 1/12 of the mass of an atom of carbon-12....
from 225.0339 u

Atomic mass unit

The unified atomic mass unit , or dalton or, sometimes, universal mass unit, is a Units of measurement of mass used to express atomic weight and molecular masses....
(²²⁵Np) to 244.068 u (²⁴⁴Np). The primary decay mode before the most stable isotope, ²³⁷Np, is electron capture

Electron capture

Electron capture is a decay mode for isotopes that will occur when there are too many protons in the atomic nucleus of an atom and insufficient energy to emit a positron; however, it continues to be a viable decay mode for radioactive isotopes that can decay by positron emission....
(with a good deal of alpha emission), and the primary mode after is beta emission. The primary decay product

Decay product

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
) isotopes (alpha emission produces element 91, protactinium

Protactinium

Protactinium is a chemical element with the symbol Pa and atomic number 91. Its longest-lived isotope has a half-life of 32,760 years....
, however) and the primary products after are element 94 (plutonium

Plutonium

Plutonium is a rare transuranic radioactive chemical element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when plutonium oxide....
) isotopes.

²³⁷Np is fissionable. ²³⁷Np eventually decays to form bismuth

Bismuth

Bismuth is a chemical element that has the symbol Bi and atomic number 83. This heavy, brittle, white crystalline trivalent poor metal has a pink tinge and chemically resembles arsenic and antimony....
-209, unlike most other common heavy nuclei which decay to make isotopes of lead

Isotopes of lead

Lead has four stable isotopes - 204Pb, 206Pb, 207Pb, 208Pb and one common radiogenic isotope 202Pb with a half-life of ~53,000 years....
. This decay chain

Decay chain

In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive Decay product as a chained series of transformations....
is known as the neptunium series.

Neptunium in popular culture

When Confederate scientists in Harry Turtledove

Harry Turtledove

Harry Norman Turtledove is an United Statesn novelist, who has produced works in several genres including historical fiction, fantasy and science fiction....
's Southern Victory Series
Timeline-191

Timeline-191 is a fan name given to a series of Harry Turtledove alternate history novels, including How Few Remain as well as the Great War , American Empire , and Settling Accounts series....
of alternate-history novels, discover the 93rd element they dub it "saturnium". When American and British scientists learn of the element, they call it "neptunium" and "mosleyium" (after Henry Moseley

Henry Moseley

Henry Gwyn Jeffreys Moseley was an England physics. His main contributions to science were the quantitative justification of the previously empirical concept of atomic number, and Moseley's law....
) respectively.

Literature

Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
Lester R. Morss, Norman M. Edelstein, Jean Fuger (Hrsg.): The Chemistry of the Actinide and Transactinide Elements, Springer-Verlag, Dordrecht 2006, ISBN 1-4020-3555-1.
Ida Noddack
Ida Noddack

Ida Noddack , n?e Ida Tacke, was a German chemist and physicist. She was among the first physicists to propose nuclear fission. With her husband Walter Noddack she discovered element 75 rhenium....
: "Über das Element 93", in: Angewandte Chemie
Angewandte Chemie

Angewandte Chemie is a weekly peer-reviewed chemistry scientific journal that covers all disciplines of chemistry. Its impact factor is 10.031 , which is the highest value for a chemistry-specific journal that publishes original research....
1934, 47, 653–655.

External links

(also used as a reference)
, U.S. Department of Energy Research News