Uncertainty analysis of the fuel compact of the prismatic high temperature gas-cooled reactor test problem using SCALE6.1

Abstract

The IAEA CRP UAM on HTGRs has established international activities grouped into phases for the evaluation of HTGRs through sensitivity and uncertainty assessments. The assessments range from Reactor physics, Thermal-hydraulics and Depletion calculations. This study focuses on Reactor physics calculations and deals with calculations performed on the fuel pin cell model of the MHTGR-350 MW reference reactor design. The calculations were performed using the KENO-VI and TSUNAMI-3D codes, which are part of the SCALE 6.1 code package. The KENO-VI calculates the criticality of the pin cell, while TSUNAMI-3D uses solutions obtained from forward and adjoint calculations to provide additional sensitivity and uncertainty information. The Reactivity-equivalent physical transformation RPT methodology was used to solve for the double-heterogeneity effect, which is an issue presented by HTGR concepts. Both the standard and modified RPT methods were investigated. It was found that the modified RPT model provides a much closer representation of double-heterogeneous model in terms of the neutron flux distribution compared on base-value calculations. The infinite multiplication factor for the homogeneous MHTGR-350 KENO-VI model underestimates the corresponding double-heterogeneous case in all temperature states. In all TSUNAMI-3D models of the fuel pin cell, it was found that the main contributor to the uncertainty in infinite multiplication factor was the capture of neutrons by the 238U nuclei to release a gamma ray. The computational results obtained in this study were compared with the existent body of literature