Specifications include physical properties (homogeneity, grain size, specific surface area), plutonium content (>86%) and chemical impurities (<5000 ppm as an element) and specific у activity from fission products (<37 x 103 Bq/gPu).

Reprocessed plutonium includes isotopes from mass 238 to 242, all with long half-lives (>6 x 103 years) except for plutonium-238 (88 years) and plutonium-241 (14.4 years).

The quality of the plutonium that is available for recycling is a function of the time spent in reactor because of fission and the formation of the higher isotopes. Typically, about two thirds of the Pu-239 that is created during irradiation of U-238 in a light water reactor is lost through fission so that about 1/3 is available for recycling. High burn-up fuel produces greater concentrations of Pu-241. Whilst this may fission it can also decay to americium-241, which is neutron­absorbing and an a and у emitter. To avoid a build-up of Am-241, which can place onerous restrictions on the handling of plutonium in MOX manufacturing plants, reprocessed plutonium is usually made into MOX fuel as soon as possible. If instead, plutonium is stored for a long time, it may be necessary to remove the americium chemically to avoid such problems. To avoid transport of liquids, plutonium is delivered for storage or to the MOX plant as solid PuO2.