Abstract
Large Break Loss of Coolant Accident (LBLOCA) is the most severe design base accident. The safety systems have to ensure the peak cladding temperature below the critical limit during LBLOCA. Therefore, the simulation of LBLOCA is important for NPP safety analysis. NRC is one of the most important regulatory agency and also lay down many regulations. In the past time, conservative approach was widely used. Most of the countries followed the 10CFR50.46 Appendix K methodology for the LOCA analysis. Nowadays, in order to make the analysis results close to the physical reality, best-estimate plus uncertainty (BEPU) approach is getting popular. The main objective of this research is to establish a BEPU approach for Maanshan NPP LOCA analysis using RELAP5/MOD3.3. The analysis method will be divided into two part. First of all, a basic LOCA analysis will be performed to learn the thermal-hydraulic phenomenon during LOCA, and learn how the thermal-hydraulic phenomenon influence the cladding temperature. Second, uncertainty analysis will be performed to consider the deviations in the real situation. Also, sensitivity analysis will be done to learn how the system deviations affect the cladding temperature.