Criticality analysis with burnup credit for APR1400 in the Republic of Korea

Criticality analysis for the spent fuel pool storage racks of APR1400, Advanced Power Reactor with 1400 MWe capacity for the next generation reactors in Korea, has been performed with the introductions of burnup credit and neutron-absorbing material to maximize spent fuel storage capacity in a given area. The main purpose of this analysis is to determine the minimum burnup necessary for a fuel assembly with a specific initial enrichment and minimum cooling time to be placed in the spent fuel storage rack. In this analysis, the SCALE 4.4 code system has been used. Also, the biases and uncertainties evaluated through validation calculations for both isotopic predictions and criticality calculation have been taken into account in the criticality evaluation. All of the key reactor operating parameters, such as moderator density, soluble boron level, fuel temperature, specific power, and operating history have been selected in a conservative way for the criticality analysis. The analysis results showed that the spent fuel storage rack of APR1400 is designed to achieve the high storage density by using burnup credit concept and poison material. (author)