New separation technologies for advanced nuclear fuel cycles
Worldwide partitioning and transmutation (P&T) research aims to maximize the fission energy gain from nuclear fuel while minimizing long term radiotoxicity of nuclear fuel waste. Studies include new methods and facilities where actinides (e.g. Np, Pu, Am, Cm) and some fission products (e.g. I, Tc) are separated and transmuted to short lived or stable forms. According to the best case scenarios estimated for P&T, the high level waste radiotoxicity could be reduced by a factor of 100 (OECD/NEA estimate). Current partitioning methods include hydrometallurgical (e.g. UREX, PUREX) and pyrometallurgical methods used to separate either individual nuclides or groups of nuclides. The majority of the hydrometallurgical methods are based on solvent extraction, resulting in large amounts of secondary waste. The limited radiolytic stability of organic extractants is another drawback of solvent extraction. Inorganic ion exchange materials generally offer superior thermal and radiation resiliency over organic ones and an alternative or supplementary method to the existing solvent extraction techniques.
There is the problem of separating trivalent actinides from trivalent lanthanides. In short, the transmutation of actinides needs a strong separation of lanthanides, because of the Ln's large number and nuclear cross-sections, which together thwart the efficient burning of actinides. The separation of the trivalent elements in these groups is not trivial because of their similarities in their chemistry.
This is where our unit of Radiochemistry comes in. We use our decades of expertise in ion exchange materials to support the partitioning research, to facilitate the transmutation of actinides in new or upcoming reactor types. Currently we study promising inorganic ion exchange materials that work in strong acids and have capability of trivalent An/Ln uptake and separation from each other.