Passivation of Long - Lived Nuclides - the State - of – the - Art

An extensive use of nuclear methods in many fields of human activity caused a large amount of long-lived nuclides (LLN) which have been accumulated up to now as the so-called radioactive wastes (RW). The main sources of these RW are nuclear power, different military devices, medical, technical and research applications. The successful and quick enough solution of the RW problem is of great importance for future nuclear power. Although there is a great number of LLN in spent nuclear fuel a relatively small part of them only is regarded as presenting a severe environmental risk. Just these LLN are usually roughly divided into two groups for reason of potential utility and two following parallel ways of their reduction are recently delineated: 1) transmutation (or transformation by means of nuclear reactions) of long-lived fission fragments, such as 99Tc, 129I, 90Sr and 135Cs, which are useless for further energy production but danger for human health, by neutron capture and following β decay into stable ones, and 2) incineration of transuranic nuclides by means of nuclear fission in nuclear reactors. Moreover, according to rather commonly accepted consensus both these ways should be performed simultaneously in the so-called accelerator-driven system, i.e. sub-critical fast nuclear reactor or reactor assambly. In the work we outline the physics background of optimal transmutation of RW and overview the main results of transmutation studies conducted at several nuclear centres. We also mention the main trends in present transmutation investigations.

Keywords:

passivation , long-lived nuclides , accelerator driven systems