Chemistry challenges in the back end of nuclear fuel cycle

The spent nuclear fuel contains a large number of elements formed mainly due to nuclear fission and activation. Majority of the element formed are radioactive in nature and some of them possess long term radio toxicity due to their large half lives. Two types of nuclear fuel cycles are followed worldwide, viz. once through and closed. Our country opted for the closed nuclear fuel cycle, where the unburnt fissile elements (U, Pu) are recovered using tri-n-butyl phosphate based PUREX process. The concentrate of the PUREX raffinate containing the remaining fission and activation products along with the structural materials is known as the high level waste (HLW) which contains >99% of the radioactivity generated in the nuclear reactor. Presence of the lanthanides hinders the transmutation process of the minor actinides due to large neutron absorption cross section of some of the lanthanide isotopes. Separation of the minor actinides from the lanthanides is therefore, an essential step prior to their transmutation