Abstract
A three dimensional computation fluid dynamics (CFD) code, GASFLOW, is applied to analyze the hydrogen risk for Qinshan-II nuclear power plant (NPP). In this paper, the effect of spray modes on hydrogen risk in the containment during a large break loss of coolant accident (LBLOCA) is analyzed by selecting three different spray strategies, that is, without spray, with direct spray and with both direct and recirculation spray. A strong effect of spray modes on hydrogen distribution is observed. However, the efficiency of the passive auto-catalytic recombiners (PAR) is not substantially affected by spray modes. The hydrogen risk is significantly increased by the direct spray, while the recirculation spray has minor effect on it. In order to simulate more precisely the processes involved in the PAR operation, a new PAR model is developed using CFD approach. The validation shows that the results obtained by the model agree well with the experimental results.
Highlights
During severe accidents, hydrogen can be generated in watercooled reactors by metal-steam reaction
In most studies presented in open literatures, including lumped parameter code analysis and computation fluid dynamics (CFD) code analysis, the passive auto-catalytic recombiners (PAR) is simulated by introducing energy and mass source terms obtained from empirical correlations
According to the state-of-art report on PAR proposed by the PARSOAR project [2], a theoretical PAR model is recommended for the CFD analysis codes, such as GASFLOW, TONUS
Summary
Hydrogen can be generated in watercooled reactors by metal-steam reaction. The condensation introduced by the operation of the containment spray reduces the steam concentration, which leads to an increase of the hydrogen concentration and adds to the hydrogen combustion or detonation risk. A threedimensional CFD code GASFLOW [1] is utilized to simulate the gas mixing and distribution in the LBLOCA and to evaluate the effect of the containment spray on the hydrogen risk. Two other cases assuming different containment spray operation strategies are involved in this paper. In most studies presented in open literatures, including lumped parameter code analysis and CFD code analysis, the PAR is simulated by introducing energy and mass source terms obtained from empirical correlations. A PAR model is developed based on the CFD approach, in order to provide more insight into the processes inside a PAR
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