Initial Results of Scaled MHTGR Lower Plenum CFD Analysis

Abstract

The High Temperature Test Facility (HTTF) at Oregon State University (OSU) is a 1:64 volume, 1:1 temperature scaled experimental facility used to model the General Atomics Modular High Temperature Gas Reactor (GA-MHTGR) design during steady state and accident transient scenarios. One item of particular concern during steady state operation for this design is the potential existence of “hot-spots” in the lower plenum which could, over long-term operation, pose a risk to the integrity of the lower plenum support posts. Using Star-CCM+ for CFD modeling, this paper will investigate the velocity and temperature profiles within the lower plenum of the HTTF facility using fixed boundary conditions based on full power steady state test conditions. The objective of this modeling is to identify potential areas of hot-spot formation. This is part of the ongoing Thermal hydraulic code validation benchmark for high temperature gas-cooled reactors using HTTF data, a Nuclear Energy Agency (NEA) Verification and Validation (V&V) Benchmark project using high quality experimental data from the HTTF experiments at OSU to quantify accuracy and uncertainty in thermal hydraulics calculations using CFD and systems codes; later references to “The Benchmark” in this paper shall refer to this project.