NUCLEAR WASTE TRANSMUTATION

Waste management strategies foresee the use of deep geological repositories either for final disposal of irradiated fuel or, after reprocessing and reuse of U and Pu, for final disposal of long-lived radioactive materials. In the second case, partitioning and transmutation of these materials can be considered to reduce the impact of radiation on man due to the storage. On the basis of the SPIN programme developed by CEA in this field, the main features of transmutation will be presented. To reduce the long-term radiotoxicity, Pu, minor actinides and some long-lived fission products have to be transmuted. To assess the feasibility of such transmutation in reactors or advanced systems, one has to consider constraints on the neutron balance, safety, the fuel cycle, technology and cost. Goals are to use every long-lived element with a minimized production of other long-lived elements in order to obtain an appreciable radiotoxicity reduction. It implies multirecycling of Pu which favours fast neutron reactors and different strategies of multirecycling for Np, Am, Cm. Multirecycling makes the results are strongly dependent on losses. Research to obtain the high partitioning efficiency needed are in progress. Calculations suggest that hybrid systems could be efficient to transmute fission products.