Structural Safety Assessment of Solution Reactor under Hydrogen Explosion Accident

The risk of hydrogen explosion accident in solution reactor system is high, because both hydrogen and oxygen are released simultaneously from the solution reactor vessel during normal operation. Once hydrogen explosion accident occurs, the overpressure and temperature loads induced by explosion could threaten the integrity and security of radioactive containment boundary. Thus, the structural safety assessment in the event of a hydrogen explosion accident is a key question, which is highly concerned by both designers and nuclear safety reviewers. In this paper, a multi-subject coupling analytical process of structural safety assessment under hydrogen explosive load was presented, which considered chemistry, thermodynamics and mechanics, and this multi-subject coupling analytical process was applied to the structural safety assessment of solution reactor system successfully. Firstly, the governing equation numerical simulation was built up based on computational fluid dynamics (CFD) method and combustion model to simulate hydrogen explosion behaviors. Considering the solution reactor system consisted of vessel and pipelines, the hydrogen explosion behavior in a narrow channel experiment and in a large-scaled vessel experiment was simulated respectively, and the numerical simulation results, such as overpressure and flame front speed, were compared with experimental data to verify the reasonableness and accuracy of numerical simulation method. Then, the authors established the full-scaled numerical model of solution reactor system and simulated the overpressure and temperature rise in the event of a hydrogen explosion accident, using the numerical method above. The initial hydrogen volume concentration, pressure and temperature derived from accident analysis, two ignition positions (the outlet of reactor vessel and the end of pipeline) were taken into account. Furtherly, the overpressure and temperature induced by hydrogen explosion were applied to the radioactive containment boundary, and the structural dynamic response of solution reactor under hydrogen explosive load was obtained. The results show that the validation of the simulation of hydrogen explosion in narrow channel experiment and large-scaled vessel experiment is verified, and the calculated result can fit well with experimental data. It proves that the numerical method above is accurate and is applicable to solution reactor system. The simulation of hydrogen explosion in solution reactor system presents that a significant overpressure and temperature rise occurs within the radioactive containment boundary. The explosive hazard is greater when the ignition position is located at the end of pipeline. However, even the worse explosive load is unable to undermine the integrity of radioactive containment boundary, the solution reactor system can maintain safety in the event of hydrogen explosion accident.