Weapons-grade nuclear material: Difference between revisions

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Actinides and fission products by half-life v t e
Actinides^[1] by decay chain				Half-life range (a)	Fission products of ²³⁵U by yield^[2]
4n	4n + 1	4n + 2	4n + 3	Half-life range (a)	4.5–7%	0.04–1.25%	<0.001%
²²⁸Ra^№				4–6 a		¹⁵⁵Eu^þ
²⁴⁸Bk^[3]				> 9 a
²⁴⁴Cm^ƒ	²⁴¹Pu^ƒ	²⁵⁰Cf	²²⁷Ac^№	10–29 a	⁹⁰Sr	⁸⁵Kr	^113mCd^þ
²³²U^ƒ		²³⁸Pu^ƒ	²⁴³Cm^ƒ	29–97 a	¹³⁷Cs	¹⁵¹Sm^þ	^121mSn
	²⁴⁹Cf^ƒ	^242mAm^ƒ		141–351 a	No fission products have a half-life in the range of 100 a–210 ka ...
	²⁴¹Am^ƒ		²⁵¹Cf^ƒ^[4]	430–900 a
		²²⁶Ra^№	²⁴⁷Bk	1.3–1.6 ka
²⁴⁰Pu	²²⁹Th	²⁴⁶Cm^ƒ	²⁴³Am^ƒ	4.7–7.4 ka
	²⁴⁵Cm^ƒ	²⁵⁰Cm		8.3–8.5 ka
			²³⁹Pu^ƒ	24.1 ka
		²³⁰Th^№	²³¹Pa^№	32–76 ka
²³⁶Np^ƒ	²³³U^ƒ	²³⁴U^№		150–250 ka	⁹⁹Tc^₡	¹²⁶Sn
²⁴⁸Cm		²⁴²Pu		327–375 ka		⁷⁹Se^₡
				1.53 Ma	⁹³Zr
	²³⁷Np^ƒ			2.1–6.5 Ma	¹³⁵Cs^₡	¹⁰⁷Pd
²³⁶U			²⁴⁷Cm^ƒ	15–24 Ma		¹²⁹I^₡
²⁴⁴Pu				80 Ma	... nor beyond 15.7 Ma^[5]
²³²Th^№		²³⁸U^№	²³⁵U^ƒ№	0.7–14.1 Ga	... nor beyond 15.7 Ma^[5]
₡, has thermal neutron capture cross section in the range of 8–50 barns ƒ, fissile №, primarily a naturally occurring radioactive material (NORM) þ, neutron poison (thermal neutron capture cross section greater than 3k barns)

A weapons-grade substance is one that is pure enough to be used to make a weapon or has properties that make it suitable for weapons use. Weapons-grade plutonium and uranium are the most common examples, but it may also be used to refer to chemical and biological weapons. Weapons-grade nuclear material causes the most concern, but plutonium and uranium have other categorizations based on their purity.

Only certain fissile isotopes of plutonium and uranium can be used in nuclear weapons. For plutonium, it is plutonium-239 (Pu-239), while uranium has uranium-233 (U-233) and uranium-235 (U-235).

Countries that produce weapons-grade nuclear material

Because of the immense costs and difficulties of building a manufacturing facility sufficient to produce weapons-grade nuclear material, very few countries have the capability of building facilities capable of making weapons-grade nuclear material.

The only countries with facilities manufacturing weapons-grade nuclear material today are The United States, The United Kingdom, France, India, Germany, Russia, North Korea, Pakistan, Israel and China. Syria and Iran allegedly also have or are developing facilities. Of these countries, only the governments of France and Russia are known to sell their manufacturing expertise to other countries.

Because each manufacturing process is unique, any weapons-grade nuclear material can be reliably traced back to its exact manufacturing origin by analyzing the composition and impurities in the material.

Weapons-grade uranium

U-235 is made weapons-grade through isotopic enrichment. It only makes up 0.7% of natural uranium, with the rest being almost entirely uranium-238 (U-238). They are separated by their differing masses. Highly enriched uranium is considered weapons-grade when it has been enriched to about 90% U-235.

U-233 is produced from thorium-232 by neutron capture. It can be made highly pure because it can be chemically separated from Th-232 rather than by mass, which is far easier. Therefore, there is no weapons-grade concentration for U-233. Since it can relatively easily be made pure, it is regulated as a special nuclear material only by the total amount present rather than by concentration or concentration combined with the amount. Uranium-232 is a contaminant that is present only in small amounts, but whose highly radioactive decay products like thallium-208 make handling more difficult.

Weapons-grade plutonium

Pu-239 is produced artificially in nuclear reactors when a neutron is absorbed by U-238. It can then be separated from the uranium in a nuclear reprocessing plant.

Weapons-grade plutonium is defined as being predominantly Pu-239 with less than 7% Plutonium-240 ^{[citation needed]}. Pu-240 is produced when Pu-239 absorbs an additional neutron and fails to fission. Pu-240 and Pu-239 are not separated by reprocessing. Pu-240 has a high rate of spontaneous fission, which can cause a nuclear weapon to predetonate. To reduce the concentration of Pu-240 in the plutonium produced, weapons program plutonium production reactors irradiate the uranium for a far shorter time than is normal for a nuclear power reactor. More precisely, weapons-grade plutonium is obtained from uranium irradiated to a low burnup.

This represents a fundamental difference between these two types of reactor. In a nuclear power station, high burnup is desirable. Power stations such as the obsolete British Magnox and French UNGG reactors, which were designed to produce either electricity or weapons material, were operated at low power levels with frequent fuel changes using online refuelling to produce weapons-grade plutonium. Such operation is not possible with the light water reactors most commonly used to produce electric power. In these the reactor must be shut down and the pressure vessel disassembled to gain access to the irradiated fuel.

While it has been claimed ^[who?] that spent LWR fuel could be reprocessed to produce plutonium that, while not weapons grade, could be used to produce a nuclear explosion, this has never been demonstrated. In particular, a 1962 test at the US Nevada Proving Grounds using non-weapons-grade plutonium used plutonium produced in a Magnox reactor^{[citation needed]}. The actual plutonium composition, and the yield of this test, have not been disclosed.

Occasionally, low-burnup spent fuel has been produced by a commercial LWR when an incident such as a fuel cladding failure has required early refuelling. If the period of irradiation has been sufficiently short, this spent fuel could be reprocessed to produce weapons grade plutonium.

Other uses

Less frequently, weapons-grade refers to a substance used in chemical warfare or an organism used in biological warfare. A chemical that is weapons-grade must be of a high enough purity and be relatively free of contaminants. When an organism, such as a bacterium or virus, is weapons-grade, it means that it is a strain of that species that is suitable for weapons use. This may mean that it has been made more infectious or deadly. It may also mean that person-to-person transmission has been made more difficult, which helps prevent a country's own troops and citizens from becoming infected.

Colloquially, 'weapons-grade' is used to describe something unusually potent (e.g., Habanero chilis) or offensive (e.g., shock sites).

External links

Reactor-Grade and Weapons-Grade Plutonium in Nuclear Explosives, Canadian Coalition for Nuclear Responsibility
Nuclear weapons and power-reactor plutonium, Amory B. Lovins, February 28, 1980, Nature, Vol. 283, No. 5750, pp. 817-823
Garwin, Richard L. "The Nuclear Fuel Cycle: Does Reprocessing Make Sense?". In B. van der Zwaan (ed.). Nuclear energy. p. 144. But there is no doubt that the reactor-grade plutonium obtained from reprocessing LWR spent fuel can readily be used to make high-performance, high-reliability nuclear weaponry, as explained in the 1994 Committee on International Security and Arms Control (CISAC) publication.

^ Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.
^ Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.
^ Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk²⁴⁸ with a half-life greater than 9 [years]. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."
^ This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".
^ Excluding those "classically stable" nuclides with half-lives significantly in excess of ²³²Th; e.g., while ^113mCd has a half-life of only fourteen years, that of ¹¹³Cd is eight quadrillion years.

[1] Plus radium (element 88). While actually a sub-actinide, it immediately precedes actinium (89) and follows a three-element gap of instability after polonium (84) where no nuclides have half-lives of at least four years (the longest-lived nuclide in the gap is radon-222 with a half life of less than four days). Radium's longest lived isotope, at 1,600 years, thus merits the element's inclusion here.

[2] Specifically from thermal neutron fission of uranium-235, e.g. in a typical nuclear reactor.

[3] Milsted, J.; Friedman, A. M.; Stevens, C. M. (1965). "The alpha half-life of berkelium-247; a new long-lived isomer of berkelium-248". Nuclear Physics. 71 (2): 299. Bibcode:1965NucPh..71..299M. doi:10.1016/0029-5582(65)90719-4.
"The isotopic analyses disclosed a species of mass 248 in constant abundance in three samples analysed over a period of about 10 months. This was ascribed to an isomer of Bk²⁴⁸ with a half-life greater than 9 [years]. No growth of Cf²⁴⁸ was detected, and a lower limit for the β⁻ half-life can be set at about 10⁴ [years]. No alpha activity attributable to the new isomer has been detected; the alpha half-life is probably greater than 300 [years]."

[4] This is the heaviest nuclide with a half-life of at least four years before the "sea of instability".

[5] Excluding those "classically stable" nuclides with half-lives significantly in excess of ²³²Th; e.g., while ^113mCd has a half-life of only fourteen years, that of ¹¹³Cd is eight quadrillion years.

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@@ Line 32: / Line 32: @@
 Less frequently, weapons-grade refers to a substance used in [[chemical warfare]] or an [[organism]] used in [[biological warfare]]. A chemical that is weapons-grade must be of a high enough purity and be relatively free of contaminants. When an organism, such as a [[bacteria|bacterium]] or [[virus]], is weapons-grade, it means that it is a [[strain (biology)|strain]] of that [[species]] that is suitable for weapons use. This may mean that it has been made more [[infection|infectious]] or deadly. It may also mean that person-to-person transmission has been made more difficult, which helps prevent a country's own troops and citizens from becoming infected.
-Colloquially, 'weapons-grade' is used to describe something unusually potent (e.g., [[Habanero chili]]s) or offensive (e.g., [[shock site]]s such as [[Goatse.cx]]).
+Colloquially, 'weapons-grade' is used to describe something unusually potent (e.g., [[Habanero chili]]s) or offensive (e.g., [[shock site]]s).
 ==External links==