A Phased Array Ultrasonic Testing Technique for the Inspection of Nozzle Welds in the Nuclear Industry

Regular, in-service inspection is important to verify the integrity of welded nozzle sections in the nuclear industry. Nozzle sections are susceptible to crack growth due to thermal fatigue and stress corrosion. Early detection of cracks is therefore essential to ensure the continued safe operation of the facility. The aim of this project is to design an inspection system that is capable of reducing the inspection times, improving defect detectability and sizing and reducing human intervention. This will reduce the risk of exposure of the workforce to harmful radiation, reduce the requirement for robotic manipulation and consequently reduce the size and cost of robotic deployment systems. In order to reduce the time and cost of such inspections, there is a need to develop a system capable of performing a full inspection of nozzles without the need to change probes. This paper will present the initial studies of the inspection technique, concentrating on the ultrasonic simulation using CIVA, carried out to determine the most appropriate phased array probe and its detection capabilities. The work includes the assessment of design parameters including the beam propagation through the material, the beam coverage and the defect response at critical areas of the nozzle.