Development of an automated scanner and 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 can be 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 facilities. 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. The aim of this project was to design an inspection system that is able to achieve the following: reduce the inspection times, improve defect detectability and sizing, and reduce human intervention, which will reduce workforce radiation uptake. The developed automated system reduces the requirement for complex robotic manipulation and consequently reduces the size and cost of robotic deployment systems. This paper will present the inspection technique development and ultrasonic simulation using CIVA that was carried out to determine the most appropriate phased array probe and its detection capabilities. The parameters that are assessed are the beam propagation through the material, the beam coverage and the focusing characteristics of the beam as well as the defect response at critical areas of the nozzle. Furthermore, the developed automated inspection system and its functionalities will be presented together with experimental results from nozzle mock up samples with simulated defects at the nozzle to vessel weld.