Ductile crack initiation under mechanical and thermal loads

The emergency core cooling system (ECCS) operates when a hypothetical severe thermal transient occurs in a nuclear reactor pressure vessel and the hot wall of pressure vessel is cooled by cold ECCS water. At this time, the vicinity of the inner surface is subjected to high thermal stresses owing to constraint of components and temperature gradients. Especially, under the pressurized thermal shock (PTS) condition, the membrane stress induced by pressure is added. PTS problem is one of the most important issues for integrity of the nuclear reactor pressure vessel.