Research on Ultrasonic Inspection of the Narrow gap welds of the Main Coolant Line (MCL) in Chinese Evolutionary Pressurized Reactor (CEPR) Nuclear Power Plant

摘要

The Main Coolant Line (MCL) is the pressure boundary of the reactor coolant loop in the pressurized reactor nuclear power plant, and the weld quality determines the integrity of the pressure boundary. Nowadays, the narrow gap gas tungsten arc welding (GTAW) technology has taken place of the shield metal arc welding (SMAW) technology in the installation of the main pipeline. The Ultrasonic testing is one of the main methods to test the quality of the narrow gap welds. Due to the space and location limit, the specific manipulator is designed to perform ultrasonic inspections from the external surface of the Main Coolant Line welds. Techniques have been developed using conventional ultrasonic duel element focusing techniques for the inspection of thick section austenitic stainless steel. In this paper, the validation of this technique on mock-up has been performed. The qualification result shows that the selected ultrasonic technology and specific designed scanner demonstrate excellently in the mock-up and block with artificial flaws.