BFS Critical Experiment and Analysis; Analysis of BFS-62-5 and 66-1 Cores

Hazama, Taira ; Iwai, Takehiko*; Shono, Akira

A program is in progress to dispose excess weapon plutonium in BN-600 fast reactor. To support the program, a series of critical experiments that simulates plutonium loading in BN-600 (BFS critical experiment and analysis) was carried out, and has been analyzed in an international collaboration with Russian Institute of Physics and Power Engineering. This report describes analysis results of the critical experiments on the last core configurations BFS-62-5 and BFS-66-1. In addition, already-reported analysis results on BFS-62-1 to -4 cores are updated in a unified method. BFS-62-5 and 66-1 have different features such as use of MOX fuel in the central area and having the sodium plenum region above the fuel region, when compared with BFS-62-1 to -4 mainly consisting of uranium fuel. Despite the differences, major nuclear parameters were successfully analyzed with similarly good accuracy. Even the sodium void reactivity, an important safety parameter and sensitive to the core configuration change, was analyzed within nuclear data uncertainty. These results will contribute to the improvement in reliability of core design in the dismantled plutonium disposition program of Russia and the FBR feasibility study of Japan.