Study on method to achieve high transmutation of LLFP using fast reactor

Abstract

The purpose of this study is to clarify the method to achieve high transmutation rates of four long-lived fission products (79Se, 99Tc, 107Pd, and 129I) using a fast reactor. New LLFP target assemblies were invented in consideration of the suppression of thermal spikes in adjacent fuel assemblies by combining YD2 and YH2 moderators or using a thermal neutron filter material. It was clarified that the high transmutation rate of about 8%/year was achieved, if the new LLFP target assemblies of 4 nuclides were loaded in the blanket region of the sodium cooled, MOX fueled fast reactor. The feasibility of the LLFP transmutation target was clarified through experiments on material properties and fabrication of the LLFP target, YH2 and YD2 moderators.