Experimental and numerical investigation of leakage and diffusion accidents based on nuclear energy hydrogen production system

Abstract

The high-temperature gas-cooled reactor, as a fourth-generation nuclear power system, possesses a distinct advantage of high core outlet temperature, making it a viable option for large-scale, low-carbon hydrogen production. However, before this technology can be widely adopted, it is crucial to conduct a safety assessment of the nuclear hydrogen production system, considering the unique physical and chemical properties of hydrogen. This study aimed to address this requirement by implementing two experimental setups, utilizing helium as a substitute for hydrogen. Concentration distribution measurements were performed in both open spaces and inside a wind tunnel. The concentration decay rates were found to be 0.177 under windless conditions and 0.313 in windy conditions. Subsequently, numerical models were employed to validate the feasibility of leakage and diffusion calculations for subsonic leakage jets and high-pressure underexpanded leakage jets, respectively. Moreover, multiple simulation calculations were conducted to design leakage accident scenarios based on the nuclear hydrogen production system. The corresponding concentration decay patterns were summarized, and evaluation relational expressions were proposed to determine diffusion distance and explosion distance for the nuclear energy hydrogen production system, accounting for the influence of buoyancy effects and incorporating the average concentration of combustible hydrogen clouds. Lastly, considering the worst-case accident conditions of the current system, a fan reverse blowing scheme was suggested to mitigate safety risks. The findings indicated that this scheme could potentially reduce the separation distance from 479 m to 183 m. Overall, this research contributes valuable insights into the safety assessment and design of nuclear hydrogen production systems.