High-Fidelity Simulations of an Air-cooled Reactor Cavity Cooling System

Nuclear energy is increasingly being acknowledged as having a pivotal role in the global shift toward cleaner energy solutions. Among the various types of Generation IV reactors, advanced nuclear technologies such as high-temperature gas-cooled reactors (HTGRs) are particularly appealing, thanks to their high-temperature heat output and potential for cogeneration. HTGR designs incorporate passive safety systems (e.g., the Reactor Cavity Cooling System [RCCS]) that utilize natural principles to manage heat dissipation from the reactor pressure vessel (RPV) during accidents or routine shutdowns. Regulatory bodies require thorough validation of such safety systems in order to ensure they meet specified s tandards. Consequently, the industry is experiencing a pressing need for advanced simulation tools that can accurately assess the performance of these types of systems. In the literature, a knowledge gap exists concerning high-fidelity data for the RCCS, and this gap is one of the areas of focus of the present study. This research focuses on a specific RCCS designed for General Atomics’ Modular High-Temperature Gas Reactor (GA-MHTGR). Experimental studies on a scaled version of the air-cooled RCCS used in GA-MHTGR were conducted by the University of Wisconsin-Madison (UW-Madison). This work contributes to a broader initiative aimed at establishing a numerical benchmark based on the UW-Madison experiments. As a first s tep, we p erformed h igh-fidelity si mulations of the experimental facility setup in order to analyze the flow p hysics i n s uch s ystems a nd t o validate NekRS and the Multiphysics Object-Oriented Simulation Environment (MOOSE) heat transfer and radiation modules.