Sensitivity of SC-HTGR Conduction Cooldown to Reactor Cavity Cooling System Failure

The inherent passive heat removal characteristics of modular High Temperature Gas-Cooled Reactors (HTGRs) are well known. Modular HTGRs use a combination coated-particle fuel, ceramic core materials, geometry, and power level to maintain acceptable fuel temperatures for all credible operating accident conditions. Heat from the reactor vessel is radiated cavity cooling system (RCCS), which removes excess cavity. RCCS Framatome’s Steam Cycle–High Reactor (SC-HTGR) highly reliable, redundant system. Similar most other HTGR concepts, failure not considered any scenario. Nonetheless, module performance with compromised still interest. Evaluation such beyond-design-basis scenarios supports safety assessment extremely low probability events (BDBEs) as development design requirements plant emergency procedures. This study evaluates SC-HTGR during long-term depressurized loss forced circulation event without operation. Boundary conditions varied determine their effect on temperatures. Safety investment risk considerations addressed. results this indicate that impact modest since remain within limits. However, more significant could significantly exceed limits these hypothetical BDBEs.