Radiation characteristics of reactor grade platinum group metals

The paper examines the radiation characteristics of noble platinum group metals (PGMs) extracted from spent nuclear fuel (SNF) of the VVER-1000 reactor. These are the so-called reactor-grade ruthenium, rhodium and palladium. PGMs are radioactive when extracted from SNF, but after the decay cooling of ruthenium for about 27 years, and of rhodium for about 13 years, they can be used in unlimited quantities. There is no sense in decay cooling of reactor grade palladium due to its radioactive isotope 107 Pd having a half-life of 6.5 million years. As specified by regulatory documents, such palladium can be freely used only in quantities of up to 34 g. Pd is a soft beta emitter with a maximum beta particle energy of 34 keV. The calculation results show that the mean free path of beta particles from 107 Pd in palladium metal is 0.8 μm, so reactor-grade palladium emits only from the surface layer, and other electrons are absorbed in the material itself. The mean free path of electrons with an energy of 34 keV in biological tissue is about 20 μm, which does not exceed the thickness of the skin epidermiscorneous layer. Calculations have shown that the equivalent dose rate (EDR) on the surface of reactor-grade palladium is 0.04 μSv/h, which is below the public EDR value. As a result, a conclusion is made that reactor-grade palladium does not pose a danger in the event of external contact.