Predicting time-correlated leakage rates of double-sealed hatch under accident conditions in a nuclear power plant

Abstract

A gaseous circuit model is proposed for predicting the time-correlated leakage rate of double-sealed structures used in the large diameter hatches, which are considered to be the most vulnerable parts of the containment systems. The core task of the model is the determination of the instantaneous dual O-ring flow resistance, deduced from existing interfacial leakage mechanisms and combined with the effect of large flange deflection. After validation by comparison with experimental measurements, the model is used to quantitatively investigate the leakage behavior of a double-sealed hatch under various air source excitations. It is found that, the leakage related parameters all vary exponentially with time under constant pressure excitation, with higher pressures corresponding to faster system stabilization rates. However, under a dynamic accident scenario, the leakage related parameters follow the internal pressure, and a significant lag in parasitic pressure and outer leakage can be observed during the pressure decay phase.