Numerical Simulation of the Effect of Mixed Gas Temperature and Steam Injection Rate on Hydrogen Distribution at Steady State in Small Volumes

Abstract

Hydrogen may be released into the containment atmosphere of a nuclear power plant during a severe accident. Locally, high hydrogen volume fraction can be reached that can possibly cause fast deflagration or even detonation and put the integrity of the containment at risk. The measurement accuracy of hydrogen volume fraction in containment is important to judge the flammability of hydrogen in the containment during a severe accident. The experimental device for hydrogen distribution and hydrogen volume fraction measurement at steady state in small volumes will be set up in the future, it is necessary to study on the effect of mixed gas temperature and steam injection rate on hydrogen distribution at steady state in small volumes. Computational fluid dynamics (CFD) codes can be applied to predict hydrogen distribution in compartments at steady state in the containment during a severe accident. The pressure vessel is used to provide the same mixed gas as in the containment during a severe accident, and the numerical simulation is carried out for different work conditions with hydrogen-nitrogen mixture of 20% hydrogen volume fraction in the pressure vessel, investigating the effect of mixed gas temperature and steam injection rate on hydrogen distribution at steady state in small volumes. The numerical simulation results are qualitatively analyzed in the paper, the following conclusions indicate that it is no obvious stratification of hydrogen at steady state in small volumes at the work conditions (0–100, 0–120, 0–140, 0–160) with different mixed gas temperatures and it is no obvious stratification of hydrogen at steady state in small volumes at the work conditions (0.1–160, 1–160) with different steam injection rates. Therefore, mixed gas temperature and steam injection rate have almost no effect on hydrogen distribution at steady state in small volumes. The numerical simulation results can provide some data basis for the experimental device for hydrogen distribution and hydrogen volume fraction measurement at steady state in small volumes in the future, and the outcomes of the qualitatively analysis can be used for design and optimization of the experimental device, in order to develop a hydrogen volume fraction measurement system for the containment during a severe accident.