IAEA CRP on HTGR Uncertainties: Sensitivity Study of PHISICS/RELAP5-3D MHTGR-350 Core Calculations using Various SCALE/NEWT Cross-Section Sets for Ex. Ⅱ-1a

摘要

Uncertainty and sensitivity analysis is an indispensable element of any substantial attempt in reactor simulation validation The quantification of uncertainties in nuclear engineering has grown more important and the IAEA Coordinated Research Program (CRP) on High-Temperature Gas Cooled Reactor (HTGR) initiated in 2012 aims to investigate the various uncertainty quantification methodologies for this type of reactors. The first phase of the CRP is dedicated to the estimation of cell and lattice model uncertainties due to the neutron cross sections co-variances Phase Ⅱ is oriented towards the investigation of propagated uncertainties from the lattice to the coupled neutronics/thermal hydraulics core calculations Nominal results for the prismatic single block (Ex I-2a) and super cell models (Ex I-2c) have been obtained using the SCALE 613 two-dimensional lattice code NEWT coupled to the TRITON sequence for cross section generation. In this work, the TRITON/NEWT-flux-weighted cross sections obtained for Ex I-2a and various models of Ex I-2c is utilized to perform a sensitivity analysis of the MHTGR-350 core power densities and eigenvalues The core solutions are obtained with the INL coupled code PHISICS/RELAP5-3D, utilizing a fixed-temperature feedback for Ex Il-la It is observed that the core power density does not vary significantly in shape, but the magnitude of these variations increases as the moderator-to-fuel ratio increases in the super cell lattice models