METHOD FOR WATER JET PEENING OF INTERNAL STRUCTURAL MEMBER IN REACTOR PRESSURE VESSEL AND WATER JET PEENING DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent such damage as stress corrosion cracking by providing a structure where the jet containing cavitation bubbles from a nozzle is collided against a flat collision surface of a baffle body to change the direction of the jet and hit it with the surface of an internal structural member. SOLUTION: A nozzle 4 of an ascending and descending axis 6 is inserted parallel to an outer face of a shroud 23 by using an auxiliary hoist of a refueling machine. A jet 3 containing cavitation bubbles 2a from the nozzle 4 is injected downward and is collided against a flat surface of a baffle 5a near a vertical weld 17. The jet 3 collides with the vertical weld 17 as a collision jet 9a. On this occasion, it is preferable that the distance L between the tip of the nozzle 4 and the collision surface of the baffle 5a is 50 or less times as long as the injection aperture of the nozzle. Minute cavitation bubbles 2a that did not collapse when they collided with the baffle body 5a grow in a collision jet 9a and collapse by high pressure in the vertical weld 17, whereby tensile residual stress of the vertical weld 17 can be reduced effectively. It is preferable that the angle between the central axis 3a of the injection aperture of the nozzle 4 and the collision surface 50 of the baffle body 5a is 60 deg. or more.