INTER-GRANULAR STRESS CORROSION CRACKING IN THE HEAT AFFECTED ZONE OF THE PRESSURIZER SPRAY LINE PIPING OF A PRESSURIZED WATER REACTOR

A circumferential crack was detected during an in-service inspection of the pressurizer spray line piping of a pressurized water reactor (PWR). Destructive investigation revealed an inter-granular crack with a depth of 4.4 mm, which was propagated in the weld heat affected zone (HAZ) of a 316 stainless steel. The line is filled with hydrogenated PWR primary water, assuming oxygen stagnation is not a primary cause. The detailed initiation mechanism is still unclear, and the propagation was considered inter-granular stress corrosion cracking of extremely high hardened HAZ. The potential cause of the high hardness is the superimposition of high heat input and constrain condition of nozzle shape.