Numerical analysis of alternative operating temperatures on a modular helium reactor under accident conditions

An MHR (Modular Helium Reactor) can cool down by itself under any accident conditions even if active shutdown cooling systems are inoperative. The purpose of the study is to develop a numerical model to analyze the decay heat removal capabilities of an MHR. This study presents a comparison of coolant inlet/outlet operating temperatures (degrees C) for an MHR; (1)350/1000, (2)490/1000, (3)590/1000, (4)350/950, (5)490/950, and (6)590/ 950. The first objective is to predict the peak fuel temperature for different inlet/outlet temperatures under a depressurized cooldown accident. The second objective is to determine the effect of flow bypass gap size for all cases. To investigate the performance of different operating conditions and the sensitivity to gap size between graphite blocks, thermal-hydraulic transient simulations are performed using a commercial CFD code, Ansys Fluent. Passive cooldown under a depressurized accident is solved numerically for 100 h. The results indicate that all peak fuel temperatures are below the TRISO design limits of 1600 degrees C.

Automated summary

The study aims to predict the peak fuel temperature under different temperature conditions in a depressurized cooldown accident, and determine the impact of flow bypass gap size. The results show that all peak fuel temperatures remain below the TRISO design limits of 1600 degrees C.