Method for determining the realistic size of a crack in a containment in the case of a severe accident

Abstract

Calculations of severe accidents performed for level 2 probabilistic risk analysis (PRA-2) require the relevant leakage parameters such as location, area, flow rate, etc. Since the pressure of the medium at which the leakage occurs is probabilistic, a series of variant calculations of a severe accident is performed for the PRA‑2. However, when postulating the occurrence of a leakage, determining its size and location remains problematic. In this regard, an approach is proposed for reducing the number of variant calculations of severe accidents for the PRA‑2 to obtain its realistic results. According to conservative assumptions, a single through crack in the most stressed area of the lining is postulated, whose behavior will determine the ultimate state of the containment. The initial crack size corresponds to the leakage of the medium during the commissioning tests of the containment. Leakage parameters can thus be determined based on the assessment of the stress-strain state of the containment lining, while the ultimate state is established on the basis of the linear fracture mechanics.