BEMUSE Phase V Report Uncertainty and Sensitivity Analysis of a LBLOCA in Zion Nuclear Power Plant. OECD/NEA Report

The BEMUSE (Best Estimate Methods – Uncertainty and Sensitivity Evaluation) Programme has been promoted by the Working Group on Accident Management and Analysis (WGAMA) and endorsed by the Committee on the Safety of Nuclear Installations (CSNI). The high-level objectives of the work are:  To evaluate the practicability, quality and reliability of Best-Estimate (BE) methods including uncertainty and sensitivity evaluation in applications relevant to nuclear reactor safety  To develop a common understanding in this domain  To promote and facilitate their use by the regulatory bodies and the industry Operational objectives include an assessment of the applicability of best-estimate and uncertainty and sensitivity methods to integral tests and their use in reactor applications. The scope of the programme is to perform Large Break Loss-Of-Coolant Accident (LB-LOCA) analyses making reference to experimental data and to a Nuclear Power Plant (NPP) to address the issue of “the capabilities of computational tools” including scaling and uncertainty analysis. This report is focused on BEMUSE Phase V activities and results. In Phase I the methodologies were discussed, in Phase II the Best-Estimate calculation of a test was performed, in Phase III the uncertainties and sensitivities were analyzed for the previous test and finally, in Phase IV, the Best Estimate calculation for a NPP was developed. All these previous phases constitute the background which is intended to be used in the present phase in order to produce final uncertainty results. Nowadays, Best Estimate Plus Uncertainty Methods are broadly used worldwide, directly for licensing purposes (USA, Netherlands, Brazil, etc.) or linked to future use for licensing (Canada, Czech Republic, France, etc.). The results presented in this report conclude on the computational aspects of the comparative exercise as they are a necessary step for future uses of these methods for licensing purposes.