Subcriticality evaluation method when storing spent fuel assemblies

摘要

PROBLEM TO BE SOLVED: To provide a subcriticality evaluation method for spent fuel assemblies during storing in a container system which can transport and store spent fuel assemblies safely, surely and efficiently by assuring subcriticality in site pool or cask container system. SOLUTION: Axial neutron emission rate distribution 12 and axial burnup distribution 13 are obtained as unit data 11 for each spent fuel assembly, nuclear constants 14 for neutron transport calculation are also obtained, and axial neutron flux distribution 16 of the container system is measured in the process for containing the fuel assembly in the container system. The nuclear constants are partly adjusted so that the neutron flux 17 calculated with neutron transport calculation for a fixed neutron source mode against the container system in containing process by using the nuclear constants 14 and the axial neutron emission rate distribution is proportional to the neutron flux 16 obtained with the measurement. By using these adjusted nuclear constants 18, neutron multiplication characteristics 19 of the container system in the containing process is evaluated.