Proposal of a BEPU Methodology for Containment Safety Analysis

Abstract

Containment safety analyses are still performed using conservative assumptions due to the difficulties in modeling the phenomena associated, and/or to satisfy the regulatory bodies? requirements. Nevertheless, in order to obtain accurate predictions, realistic analyses have to be performed. In 1989, the U.S. NRC modified the licensing requirements allowing the use of realistic methods if uncertainties are identified and quantified, the so-called BEPU analyses. Therefore, a BEPU methodology specifically developed for containment analysis is proposed. Conservative assumptions are avoided by developing best estimate containment models. Uncertainties are quantified and propagated through the code in order to obtain the results accuracy. The proposed methodology is defined in a hierarchical structure, similar to the U.S. NRC Regulatory Guide 1203. It is divided in two main blocks; the first is related to the best estimate model setting; and the second to the uncertainty treatment.