Modelling of thermal and flow stratification for reactor pressure vessel pressurised thermal shock

A Pressurised Thermal Shock (PTS) occurs when the hot vessel wall of a pressurised water reactor is exposed to low-temperature, high-pressure fluid during a transient such as Emergency Coolant Injection (ECI) following a Loss of Coolant Accident (LOCA). Overcooling events have the potential to threat safety because the resulting high thermal stress, along with irradiation induced loss of ductility and stress-concentrating faults, or macro-cracks, can result in a through-the-wall crack propagation and reactor pressure vessel failure. The problem of PTS therefore has been studied extensively. This paper presents the development and application of an analytical thermal hydraulic model for predicting the growth of PTS in the downcomer in case of ECI. A preliminary assessment of pressure vessel integrity is also presented and discussed