Abstract
This study investigates the behavior of a High-Temperature Gas-Cooled Reactor (HTGR) during a break of the helium pressure boundary event. Understanding the gas dynamics that occur during a break could help develop safety systems that reduce the probability of air entering the reactor core. To achieve this objective, experimental studies were conducted in a scaled-down HTGR experimental facility to provide information on the air-helium gas mixture within the confinement building and the impact of the ventilation system on the helium/air gas concentration following the depressurization event. The study evaluated different configurations, including active ventilation time scales, break sizes, and locations. The analysis of the active ventilation time revealed that a ventilation time of 22 s produced positive results, and smaller break sizes resulted in longer depressurization times, which improved the ventilation process. The orientation and elevation of the breaks had little effect on the oxygen concentration in the cavity but did impact the gas velocities.
•The research study examines the gas dynamics within the confinement building during an accident scenario, specifically when a break occurs in the helium pressure boundary of an HTGR.•A 1/20th scaled-down experimental facility for a high-temperature gas-cooled reactor has been designed and constructed, modeled after the General Atomics 600 MWth GT-MHR prototype. Its purpose is to characterize the gas dynamics within the confinement building during accident scenarios.•Experimental data, including fluid temperature, flow velocity, pressure, and oxygen concentration, were systematically collected subsequent to the depressurization of the scaled-down reactor pressure vessel. This data offers valuable insights into the concentrations of air and helium gas, contributing to developing safety recommendations for real-world HTGR reactor designs.