Subcriticality evaluation method, subcriticality evaluation device and subcriticality evaluation program

摘要

PROBLEM TO BE SOLVED: To conservatively and easily evaluate the subcriticality of a highly burned fuel loaded in a radioactive material containment vessel from the viewpoint of safety design in consideration of the burnup credit of the fuel. SOLUTION: In a fuel subcriticality evaluation method, a step of setting a fuel assembly model having a single fuel enrichment and a fuel assembly model are used, and a first method is used based on a first combustion condition. A step of calculating the composition parameter of 1, a step of calculating the first effective multiplication factor of the fuel based on the first composition parameter, a step of setting the envelope model fuel, and a second effect of the envelope model fuel. When the step of calculating the multiplication factor and the determination that the first effective multiplication factor is equal to or higher than the second effective multiplication factor, the second is based on the conservative second combustion condition using the fuel assembly model. It is provided with a step of calculating the composition parameter of the above and a step of calculating the third effective multiplication factor of the fuel based on the second composition parameter. [Selection diagram] FIG. 7