ULTRASONIC FLAW DETECTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detection method that can improve position precision of a defect detected at a nozzle corner part without being influenced by the curvature of a nozzle external surface.

SOLUTION: A linear array probe 2 is placed on an external surface of a cylindrical part 36 of a nozzle 35 joined to a reactor pressure vessel 34, and scanned in a peripheral direction of the nozzle 35. On the basis of information on a plurality of delay time patterns, ultrasonic waves transmitted from respective vibrators of the linear array probe 2 into the nozzle 35 are scanned in an axial direction of the nozzle 35 such that focus positions of the respective ultrasonic waves are changed by changing incidence directions. Consequently, the ultrasonic waves entering the nozzle 35 are propagated in a sectorial ultrasonic wave incidence area 45 to reach the nozzle corner part. A display part 26 displays display information of a reflection echo part 50 based on a reflected wave from an internal surface of the nozzle corner part and the other reflection echo part 51 based on a reflected wave from the defect respectively.

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