Weapons-grade

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 and biological weapons. Weapons-grade nuclear material causes the most concern, but plutonium and uranium have other categorizations based on their purity.

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Only certain 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). 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. 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 neutrons. 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 reactors when a neutron is absorbed by U-238. 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 test of a nuclear weapon that used reactor-grade plutonium was successfully detonated, although the 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 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.

A colloquial use of the expression among musicians (usually Saxophonists) is used to denote a mouthpiece which is a sufficient quality and design to make it suitable to play in the most musically challenging of Jazz environments, i.e. playing Rock Music. Examples include Berg Larsens. A variant of this is the name of the band Weapons Grade Pandemonium.