Development of advanced reprocessing system using highly selective and controllable precipitants; Precipitation behavior of plutonium from U-Pu solution

Morita, Yasuji  ; Kim, S.-Y.; Kawata, Yoshihisa; Ikeda, Yasuhisa*; Kikuchi, Toshiaki*

We have been developing an advanced reprocessing system for spent FBR fuels based on precipitation method using pyrrolidone derivatives, which consists of two precipitation steps; the first selective U precipitation step and the second U-Pu co-precipitation step. In the present study, precipitation behavior of Pu with pyrrolidone derivatives with high precipitation ability of N-(1,2-dimethyl)propyl-2-pyrrolidone (NDMProP), N-neopenthyl-2-pyrrolidone (NNpP) and N-cyclohexyl-2-pyrrolidone (NCP) has been examined with solutions of U-Pu mixture in order to evaluate their applicability to the second step. Since NNpP showed the highest precipitation ability for Pu(IV) and the best physical property as precipitate, NNpP would be the most appropriate precipitant for the U-Pu co-precipitation process. Precipitation of Np(IV, V, VI) with NNpP was also examined and it was found that Np(VI) could be quantitatively co-precipitated with U(VI) and Pu(IV).