Sensitivity and Uncertainty Analysis for Containment Integrity Using the COFUN Code

Abstract

A probabilistic risk assessment (PRA), which is a comprehensive stability assessment tool that includes risks from equipment failures, operator errors, and external environmental factors, is regarded as one of the reliable methods for evaluating the risk from severe accidents of nuclear power plants. A Level 2 PRA models the plant's response to the Level 1 PRA accident sequences that result in reactor core damage. Level 2 PRA for internal event is performed by the COFUN code and source term analysis of severe accidents progression is by the MELCOR code for a reference reactor. As a result of quantification, no containment failure frequency is valued at 70%, large early release frequency (LERF) is 11.1%, and Non-LERF is 18.9%. Through sensitivity analysis, factors affecting the performance and weak parts of the containment are identified. As a result of the sensitivity analysis, sensitivity is found that it was greatly affected by the value of the probability branch value of temperature induced-steam generator tube rupture (TI-SGTR). Finally, uncertainty analysis was performed to confirm the range of the uncertainty band in the result of the point estimate. These results will contribute to the design and safe operation of nuclear power plants.