Authors: O.C. Koekemoer, G.J. Nel, C.G. du Toit
Year: 2019
Industry: Nuclear & SMR
Keywords: Use FSE, Dynamic
ABSTRACT
Modelling prismatic block high temperature gas-cooled reactor units poses several challenges and typically requires significant computational resources and computational times. This is largely due to the complexity of prismatic block reactor models as these models must amongst others account for the fuel-compacts, graphite and coolant channels in fuel blocks, cross- and bypass gaps between blocks and the mixing in the lower plenum. This amount of detail however cannot be dealt with a single explicit three-dimensional model. Motivated by recent advances in the field of Computational Fluid Dynamics (CFD) and recognizing the limitations on available computing power, this article is aimed at combining the desired features of a one dimensional (1D) system code and three-dimensional (3D) CFD code. The goal is achieved by demonstrating the coupled 3D/1D CFD model that simulate the heat transfer and fluid flow in a single-channel fuel module of a prismatic block. The coupled 3D/1D model represents one sixth of a single-channel fuel model that accounts for conduction heat transfer in the solids (fuel compact and graphite moderator), convection heat transfer between the solids and the fluid (helium) and the fluid flow in the coolant channel. The validity of the coupled 3D/1D model is investigated by comparing the temperature distribution in the single-channel fuel model for a (i) uniform- and (ii) cosine power profile with the corresponding values obtained from published work as well as a full detailed 3D CFD analysis of the same specifications and setup. Since the 3D/1D models require significantly less resources than the detailed 3D CFD it can form the basis of an integrated model for the entire core.