Measuring the Ratio of ^<242>Cm to ^<244>Cm in Operating BWR Cores Using Start-Up Range Neutron Monitors

概要

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The purpose of this study is to compare the measured and calculated ratios of neutrons originating from 242Cm and 244Cm in commercial BWRs in order to evaluate the prediction error for a weakening start-up range neutron monitor (SRNM) signal due to the decay of in-core neutron sources over a ten year period. Measurements were carried out over a period of several months, using the least-squares method to fit the time series of SRNM signals with the theoretical model. Neutron sources of each fuel assembly were calculated by the macroscopic depletion model of a plant process computer. The ratios of neutrons originating from 242Cm and 244Cm detected by each SRNM were calculated by whole core fixed source calculation using the nodal expansion method. One BWR core measurement was taken at the beginning of the cycle and three BWR core measurements were taken in the middle of the cycle. A comparison of the measured and calculated ratios of 242Cm and 244Cm number densities showed reasonable agreement. The slight difference observed between the measured and calculated ratios will be discussed.
社団法人日本原子力学会の論文
2008-06-01