Plutonium

Samples available in enrichments ranging from 95% to 99.9+%, enrichments of production-grade material range from 85% to 95%. Plutonium-244. Currently, the only isotope available as a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM). (From table) (Plutonium isotopes).

Of the 15 plutonium isotopes, the two that have proven most useful are masses 239 and 238. Plutonium-239 is fissile, i.e., atoms of plutonium split upon exposure to thermal or fast neutrons. Chemical reactions can release a few electron volts of energy per atom, however, when a plutonium nucleus splits, it releases about 200 MeV of energy and two or three neutrons. This release of energy makes plutonium-239 useful for nuclear weapons and reactor fuel. In fact, in light water reactors (LWRs) much of the power originates from the fission of plutonium-239, which is produced by neutron capture in uranium-238.

Pure plutonium metal can be prepared by precipitating plutonium peroxide or oxalate, igniting the precipitate to PuO2, converting the oxide to PuF3, and reducing Pu+3 to the metal in an ignited mixture containing metallic calcium. (Plutonium)

In the past, most plutonium in DOE facilities was produced for nuclear weapons and was composed of greater than 90 wt% plutonium-239 and about 6 to 8 wt% plutonium-240. This material has been referred to as weapons grade or low exposure plutonium. It is produced on a large scale by irradiating uranium-238 in moderated production reactors. Plutonium has also been produced as a byproduct in the operation of research reactors, and commercial nuclear power plants. It is recovered and purified by solvent extraction and ion exchange processes.