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概要

Recently, it is reported that the primary water stress corrosion cracking (PWSCC) has been occurred at the nickel based alloy weld components such as stea m generator safe end weld, reactor vessel safe end weld, and so on, in PWR. Defect detection and sizing is important in order to ensure the reliable operat ion and life extension of nuclear power plants. In the reactor vessel safe end weld, it was impossible to measure crack depth of PWSCC. The crack was dete cted in the axial direction of the safe end weld. Furthermore, the crack had some features such as shallow, large aspect ratio (ratio of crack depth and le ngth), sharp geometry of crack tip, and so on. Therefore, development and improvement of defect detection and sizing capabilities for ultrasonic inspection technique have been required. Phased array UT technique was applied to nickel based alloy weld specimen with EDM notches and standard block with SDHs. Fro m the experimental results, performance of phased array linear array probe and dual matrix array probe was investigated. In the basis of the results, UT p rocedure for crack depth sizing was manufactured. Furthermore, good accuracy of defect depth sizing by phased array UT for the inside inspection was shown.

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