Hazard and operability study of cryogenic hydrogen circulation systems in China Spallation Neutron Source Phase <scp>II</scp> project

Abstract To enhance the safety of the cryogenic hydrogen circulation system at the Target Station of the China Spallation Neutron Source Phase II (CSNS‐II), a HAZOP (Hazard and Operability) analysis was conducted in accordance with IEC 61882 (Hazard and operability studies (HAZOP studies)—Application guide). Five key nodes—helium storage, liquid nitrogen storage, hydrogen storage, helium refrigerator, and hydrogen circulation—were systematically assessed. Potential deviations, causes, and consequences were identified, and risks were evaluated using a matrix‐based approach. Key hazards include overpressure, leakage, purity loss, and utility failures. With layered safety measures such as relief valves, interlocks, and alarms, all deviations are controlled within acceptable risk levels. This study supports the safer design and operation of large‐scale cryogenic hydrogen systems in spallation neutron facilities.