Advanced Large PWR LB-LOCA BEPU Analysis with RELAP5-DAKOTA

Best-estimate codes have become more attractive to people who are dedicated to reactor safety analysis. With the purpose of getting more realistic results and larger safety margins, best-estimate plus uncertainty (BEPU) analysis method was developed to replace conservative safety analysis method. For example, ASTRUM (Automated Statistical Treatment of Uncertainty Method) was developed to analyze AP1000 Large Break Loss of Coolant Accident (LB-LOCA). This paper presents a LB-LOCA BEPU analysis by means of thermal hydraulic code RELAP5 coupled with DAKOTA. Both these two codes are coupled and invoked by Symbolic Nuclear Analysis Package (SNAP). The uncertainty parameters are selected according to LB-LOCA phenomena identification and ranking table. The corresponding distributions assigned to each parameter have been extracted from different works in open literature. With Wilks’ formula, 59 cases were calculated to ensure 95 % probability coverage at 95 % confidence level. The result shows that the Advanced Large PWR can meet the acceptance criteria of LB-LOCA analysis with enough margins.