Fuel Performance Outputs Using ELESTRES Code Assessed Through GRS Uncertainty Method

Abstract

As part of establishing initial fuel conditions for New Brunswick deterministic safety analysis applications using the ELESTRES code, uncertainty analysis is performed to characterize the effects of input parameter variation. While single parameter effects could be assessed for each key parameter if they were identified and ranked in advance, the GRS method is used in this work to determine the integrated uncertainty of both multi and single-parameter effects within the same process. In this work, all uncertainty parameters (such as key fuel design/manufacture data and their variation/tolerance ranges) are changed simultaneously, according to specified subjective probability distributions. The GRS results provide statistical data of key fuel performance outputs (such as fuel centreline temperature, internal gas pressure and their variation/tolerance ranges) and regression coefficients of multiple independent input parameters, which can be used to rank key input parameters. The assessment performed ensures the key fuel performance outputs from ELESTRES are sufficiently conservative for safety analysis applications based on key input parameters identified.