Probabilistic Pressurized Thermal Shock Analysis for a Reactor Pressure Vessel Considering Plume Cooling Effect

The inner surface of a reactor pressure vessel (RPV) is assumed to be subjected to pressurized thermal shocks (PTSs) caused by the injection of emergency cooling water. The downstream is not homogeneous but typically in a plume shape coming from the inlet nozzles. In this paper, both deterministic and probabilistic methods are used to assess the integrity of a model RPV subjected to PTS. The favor code is used to calculate the probabilities for crack initiation and failure of the RPV considering crack distributions based on cracks observed in the Shoreham and PVRUF RPVs. The study shows that peak K_I of the cracks inside the plume increases about 33% compared with that outside. The conditional probability inside the plume is more than eight orders of magnitude higher than outside the plume. In order to be conservative, it is necessary to consider the plume effect in the integrity assessment.