Best Estimate Plus uncertainty approach for accident analysis - Chapter 14 of volume 1

The Best Estimate Plus Uncertainty (BEPU) constitutes an approach or a procedure aimed at making feasible the application of nuclear thermal hydraulics to the licensing and the safety evaluation processes of Nuclear Power Plants (NPP). The features of BEPU are such to make attractive the application to address any design and operational issue in NPP technology. The triggering idea for BEPU came from the adoption of Best Estimate system thermal hydraulics codes for accident analysis in NPP technology. Key features of BEPU can be summarized as: procedures for nodalization development, code and nodalization validation, addressing the scaling issue, evaluation of uncertainty, demonstrating the analyst qualification, integrating the needs from licensing, coupling of codes from different disciplines and validation of the related software, considering the latest established findings from R & D.