RCCA Ejection Accident Analysis Based on Coupled 3d Neutronics and Thermal-Hydraulics

Abstract The rod cluster control assembly (RCCA) ejection accident is one of the most important Design Basis Condition (DBC) of Pressurized Water Reactor (PWR) nuclear power plant. This accident leads to a rapid reactivity transient by inducing an uncontrolled positive reactivity, followed by a nuclear power increase and a power distribution disturbance. The nuclear power increase is limited by reactivity feedback effects, such as the Doppler feedback effect caused by the fuel temperature increase. This may result in Departure from Nucleate Boiling (DNB) among the adjacent fuel channels, and the potential failure for the fuel cladding. At present, the traditional decoupling analysis method is still used in RCCA ejection accident (REA) analysis of HPR1000, which has a high degree of design conservatism and restricts the continuous improvement of the unit’s economy and performance improvement. This paper takes a certain HPR1000 reactor as the research object, establishes a coupled 3D neutronics and thermal-hydraulics analysis method based on SMART/FLICA III-F code. The analysis process and results were compared with traditional method. The research results indicate that the coupled 3D neutronics and thermal-hydraulics analysis method is reasonable and feasible, which can more realistically simulate the core situation during the REA transient process, and can effectively release the conservatism of key parameters. On the basis of ensuring the same level of safety, it provides the possibility for improving the performance of the unit.