Fracture analysis of the set-in nozzle of a PWR reactor pressure vessel - Part 1: Determination of critical crack

In this study, fracture mechanics analysis of the set-in nozzle of a reactor pressure vessel (RPV) is being presented. The selected RPV belongs to a 300 MW pressurized water reactor (PWR). For the purpose, a wide range of elliptical surface cracks was analyzed at the nozzle-cylinder intersection under two accidental conditions of the reactor: small-break loss of coolant accident (SB-LOCA), and Rancho-Seco transient (RST). It has been demonstrated that at the location being investigated 'a = 0.05t' is the critical crack depth; where 'a' is the depth/minor axis of the crack and 't' is the thickness of the wall.