Methodology for neutronic uncertainty propagation and application to a UAM-LWR benchmark

Abstract

This work covers an important point of the benchmark released by the expert group on Uncertainty Analysis in Modeling of Light Water Reactors (UAM-LWR). This ambitious benchmark aims to determine the uncertainty in LWR systems and processes in all stages of calculation, with emphasis on multi-physics (coupled) and multi-scale simulations. Specifically, in this work, a simplified BWR core is used to propagate the uncertainty of nuclear data. Due to a high computational cost in the analysis all fuel assemblies are modeled as fresh. The propagation is subdivided into two levels i) assembly level –with SCALE6.2.1 and SAMPLER module–, and ii) core level, –with PARCSv3.2 and DAKOTA 6.3–. The first level takes into account the uncertainties contained in the master library ENDF/B-VII.1 and as a result a problem-dependent neutronic library in NEMTAB format is obtained using TXT2NTAB code. This is a friendly Matlab code developed within this work. Finally, the uncertainty contained in the neutronic library is further propagated through PARCS. A different approach is presented in this work to propagate the uncertainty between codes. Following this approach only two neutronic libraries are generated, one with the average responses and the other with their standard deviations. Then, the standard deviation and a matrix of perturbation factors are used to perturb the main neutronic parameters. A parallel work is done to propagate the thermal-hydraulic parameters in a PWR core (Mesado et al., ).