Qualification of Ultrasonic Examination for RPV Nozzle to Shell Welds of EPR Nuclear Power Plant

European Pressurized Reactor (EPR) nuclear power plant is now under construction in China. One of the biggest changes in the EPR reactor pressure vessel (RPV) is the nozzle to shell welds are designed as “set-on” principle instead of “set-in” principle in the CPR1000 units. The nozzle to shell welds of the EPR pressure vessel must be inspected according to the RSE-M code. This is necessary in order to guarantee the integrity of the primary circuit. The In-Service Inspection (ISI) program of EPR nuclear power plant demands the automatic ultrasonic inspection of the nozzle to shell welds from nozzle inner surface. This paper presents the technical characteristics of the EPR reactor vessel, and analyzes the in-service examination requirements of nozzle to shell welds. Technical solutions have been designed to perform the examination of the component. The qualification process of the ultrasonic examination of the nozzle to shell welds is also presented.