Time-dependent radiation release characteristics of irradiated nuclear fuel assemblies in Korean nuclear power plants

The time-dependent radiation release characteristics of nuclear fuel assemblies need to be understood to manage operation safely and protect workers from the radiation released over the operation period of a nuclear reactor, including its overhaul period. This study examines the time-dependent radiation release characteristics of 2 types of PWR nuclear fuel assemblies in Korea according to their burn-up. Two types of nuclear fuel assemblies considered were: a 16 x 16 fuel assembly of Ulchin units 5 and 6 (KSNP type) and a 17 x 17 fuel assembly of Kori units 3 and 4 (Westinghouse type). The 5 different burn-ups (MWD/MTU) were considered: 100, 10,000, 20,000, 30,000, and 40,000. The calculations showed that the increase rate of neutron dose distribution was relatively higher than that of the gamma dose distribution according to burn-up, while the gamma dose distributions were much higher than the neutron dose distributions. (orig.)