ICONE23-1970 CFD ANALYSIS OF THE 1/4-SCALE AIR REACTOR CAVITY COOLING SYSTEM INLET PLENUM

Abstract

The air reactor cavity cooling system (RCCS) is a safetyrelated passive decay heat removal system undergoing further development in support of the next generation of nuclear plants, specifically the very high temperature gas reactor. Recently, the University of Wisconsin (UW) designed and built a 1/4-scale air RCCS. The experimental facility at UW consists of three major components: inlet-plenum, heated riser ducts, and an outlet-plenum with exhaust ducts. Using commercial computational fluid dynamics (CFD) software, a 3-D simulation of the inlet-plenum was performed using as-built geometry and experimental data. The purpose of this study was to improve upon preliminary CFD simulations of the inlet-plenum, which initially were conducted to evaluate the fluid structure characteristics within the plenum, to assist with uncertainty evaluations of velocity transducers in the scaled experiment, and to produce CFD results for a follow-on CFD study. An informal verification and validation (V&V) methodology was followed, which included mesh refinement and iterative convergence studies. Three inlet-plenum simulations were performed as part of the mesh refinement study; the mesh sizes of the simulations ranged from 2.3 million to 9.7 million elements. Computational difficulties related to residual convergence were experienced.