Full core burn-up calculation at JRR-3 with MVP-BURN

Komeda, Masao   ; Yamamoto, Kazuyoshi ; Kusunoki, Tsuyoshi 

Research reactors use a burnable poison to suppress an excess reactivity in the beginning of reactor lifetime. The JRR-3 (Japan Research Reactor No.3) has used cadmium wires of radius 0.02cm as a burnable poison. This report describes burn-up calculations of plate fuel models and full core models with MVP-BURN, which is a burn-up calculation code using Monte Carlo method and has been developed in JAEA (Japan Atomic Energy Agency). As the results of calculations of plate models, between a model composed of one burn-up region along the radius direction and a model composed of a few burn-up regions along the radius direction, the effective absorption cross section of Cd has had different tendency on reaching approximate 40th day (10000 MWd/t). And as results of calculations of full core model, it has been indicated that k is almost same till approximate 80th day (22000 MWd/t) between a model composed of one burn-up region along the vertical direction and a model composed of a few burn-up regions along the vertical direction. However difference of Cd burn-up becomes pronounced and each k makes a difference after 80th day.