Development of a computer code to estimate the fuel rod failure using primary coolant activities of operating PWRs

A Windows computer code entitled as CAAP (Coolant Activity Analysis Program) has been developed to evaluate the number, the degree of failures, and the location of failed fuel rods using primary coolant radioactivity data obtained from operating PWRs. The iodine and noble gas activities obtained by grab sampling can be used to estimate fuel rod failures with CAAP. The validity of the computational models of CAAP has been examined using nuclear power plant data collected. For 37 cycles of PWRs for which ultrasonic inspections were performed at the end of fuel cycles, the number of failed fuel rods has been estimated with CAAP and compared with the ultrasonic inspection results. The results show that CAAP gives a better agreement with the ultrasonic test data than existing models. In addition, CAAP calculations performed to estimate the region and the burnup of the failed fuel rods for 2 cycles, whose locations of failed fuel rods were known, show that CAAP can predict both the region and the burnup of the failed fuel rods accurately