Weapons-grade 4148957 221909335 2008-06-26T17:12:58Z Mendaliv 200402 Added {{[[Template:essay-like|essay-like]]}} tag to article. using [[WP:FRIENDLY|Friendly]] {{essay-like|date=June 2008}} {{Unreferenced|date=June 2008}} '''Weapons-grade''' means that a substance 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 is also be used to refer to [[chemical warfare|chemical]] and [[biological warfare|biological weapons]]. Weapons-grade nuclear material causes the most concern, but plutonium and uranium have [[special nuclear material|other categorizations]] based on their purity. Only certain [[isotope]]s of plutonium and uranium can be used in [[nuclear weapon]]s. For plutonium, it is [[plutonium-239]] (Pu-239), while uranium has [[uranium-233]] (U-233) and [[uranium-235]] (U-235). 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 [[mass]]es. U-235 is considered weapons-grade when it has been enriched to about 90% U-235. U-233 is produced artificially by bombarding [[thorium-232]] (Th-232) with [[neutron]]s. 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. Pu-239 is produced artificially in [[nuclear reactor]]s when a neutron is absorbed by U-238. [[Plutonium-240|Pu-240]] has a high rate of [[spontaneous fission]], which can cause a nuclear weapon to predetonate, and its concentration must be less than 7% for the plutonium to be weapons-grade. It is produced when Pu-239 absorbs a neutron. To avoid this the uranium fuel in a reactor must typically be replaced four to six times per year. This is necessary because the concentration of Pu-240 rises over time and its mass and chemical properties are too similar for it to be separated from Pu-239. With any reactor, plutonium is separated from the nuclear fuel, U-235 and U-238, chemically in a [[nuclear reprocessing]] plant. It is difficult to produce weapons-grade plutonium with a [[light water reactor]] because the reactor must be shut down frequently to replace the [[nuclear fuel]] rods, so weapons-grade plutonium is generally produced in small, specialized military reactors. However, a [[Reactor_grade_plutonium_nuclear_test|test]] of a nuclear weapon that used reactor-grade plutonium was successfully detonated, although the [[nuclear weapon yield|yield]] was relatively low. 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. ==External links== *[http://www.ccnr.org/plute.html Reactor-Grade and Weapons-Grade Plutonium in Nuclear Explosives], Canadian Coalition for Nuclear Responsibility *[http://www.rmi.org/images/other/Security/S80-01_NucWeaponsAndPluto.pdf Nuclear weapons and power-reactor plutonium], [[Amory B. Lovins]], February 28 1980, [[Nature (journal)|Nature]], Vol. 283, No. 5750, pp. 817-823 [[Category:Nuclear weapons]] [[Category:Nuclear materials]] [[Category:Uranium]]