Abstract
Surface finishing methods, such as Water Jet Peening (WJP), have been applied to welds in some major components of nuclear power plants as a countermeasure against Primary Water Stress Corrosion Cracking (PWSCC). In addition, buffering, one of the methods of surface finishing, is being standardized, and thus the buffing has been also recognized as the well-established method of improving stress. On the other hand, the long-term reliability of peening techniques has been confirmed by accelerated test. However, the effectiveness of stress improvement by surface finishing is limited to thin layers and the effect of complicated residual stress distribution in the weld metal beneath the surface is not strictly taken into account for long-term reliability. This paper, therefore, describes the accelerated tests, which confirmed that the long-term reliability of the layer subjected to buffing was equal to that subjected to WJP. The long-term reliability of very thin stress improved layer was also confirmed through a trial evaluation by thermal elastic-plastic creep analysis, even if the effect of complicated residual stress distribution in the weld metal was excessively taken into account. Considering the above findings, an approach is proposed for constructing the prediction method of the long-term reliability of stress improvement by surface finishing.
