Study on the Influence of Ultra-Long ELPO for CPR1000 Unit on Rod Drop Accident

Adopting the Extended low power operation (ELPO) scheme, especially ultra-long ELPO will have a significant impact on key neutronics parameters. Since the analysis of rod drop accident requires the use of specific neutronics parameters, the results of the analysis will also be affected due to the adoption of ELPO scheme. This paper compares the rod drop accident analysis results based on key burnup points including the end point of ultra-long ELPO and the EOL point of ELPO. The results show that after implementing the ultra-long ELPO scheme, the overall DNBR margin of the nuclear power plant will be lower compared to units that have not implemented it. Special attention should be paid to the EOL point of ultra-long ELPO, as the DNBR in this condition is more severe compared to that at the end point of ultra-long ELPO.