Pulsed eddy currents in ferromagnetic pipes with cladding in nuclear power plants

Abstract

The steam and water piping in a nuclear power plant is generally covered with cladding on the outer wall of the pipes, thereby improving heat transfer efficiency. The current means of detection for ferromagnetic pipes mainly involve conventional ultrasound and ultrasonic guided waves. Prior to the detection, outer wall insulation of the pipes needs to be removed, resulting in an extended detection period and increased labor costs, which fails to meet the requirements of high-quality development of the nuclear power plant. The application of pulsed-eddy current technology in the nuclear power plant removes insulation and enables online screening without shutdown. The ability to identify defects under large lift-off is an important indicator for pulsed eddy current technology, which is of great significance for implementing pulsed eddy current in the nuclear power sector. In this paper, the Maxwell module in ANSYS is used for pipe modeling and simulation. A vertical detection coil is designed to simulate the detection capability of pulsed eddy current for flat bottom defects under large lift-off. Sample pipes from the nuclear power plant are selected for vertical pulsed eddy current testing (PECT). The PECT results are rechecked against ultrasonic thickness measurement to verify the PECT performance under the lift-off scenario and propose future development trends.