A deterministic fracture-mechanics parametric-type analysis of a generic pressurized-water reactor pressure vessel has been conducted for loading conditions imposed by a specific category of hypothetical pressurized-thermal-shock transients. The time in the life of the vessel for which the calculations were made corresponds to attainment of the limiting nil-ductility transition reference temperature specified by the U. S. Nuclear Regulatory Commission's pressurized thermal-shock-issue-related screening criteria.
The transients considered were characterized by a constant pressure and an exponential decay of the downcomer coolant temperature. The decay constant, the final temperature of the coolant, and the fluid-film heat-transfer coefficient were the variable parameters. A search was performed to determine the critical pressure corresponding to incipient crack initiation for a range of crack depths up to 20% of the wall thickness. Results indicate that the critical pressure is greater than the normal operating pressure, if the coolant final temperature is greater than 150°C.
The fracture mechanics model used in the study tends to be conservative in the sense that it ignores possible beneficial effects of warm prestressing and cladding.