Temperature and geometry impact on defect detection and sizing

Abstract

Increasing requirements to minimize the frequency and duration of shutdowns of nuclear power plants have led to the need to address the implementation of ultrasonic testing of welded pipe connections at operating temperature. In practice, the pipes are made of carbon and stainless steel. Laboratory ultrasound tests were performed on two types of test pieces with different geometry and with homogeneous and heterogenous welds. The measurement was done within a temperature range of 50°C to 200°C in increment of 50°C. The aim of the performed measurements was to verify the detection of artificial defects created by electric discharge machining (EDM) in the root area of the weld on the carbon steel side by a selected test system and an impact of the change in focal laws (FLs) due to temperature on sizing. Together with this was evaluated the influence of elevated temperature on the determination of defect dimensions and impact of the test system, including ultrasonic, cooling, and handling subsystems for detection, sizing and using in the limited space of nuclear power plants. An inspection procedure and a safe workflow were created ss part of the testing. Both procedures were necessary for testing at elevated temperatures from the point of view of occupational safety and for carrying out individual test steps to maintain the repeatability of testing. The inspection procedure was subsequently qualified.