Peening narrow nozzles of reactor pressure vessels using ultrasonic cavitation

A peening approach using ultrasonic cavitation was proposed to peen the inner surfaces of narrow nozzles of reactor pressure vessels. The working theory for the present approach was described and numerically demonstrated. A proof-of-concept experiment using a narrow nozzle and ultrasonic loading with a frequency of 20 kHz was conducted, and a noticeable improvement in residual stress was achieved at the inner surface of the nozzle. The successful demonstration in this study indicates that the present technique using ultrasonic cavitation has the potential to effectively peen the inner surfaces of long and narrow nozzles or holes at a low cost using existing conventional peening techniques.