レーザピーニング施工による微小き裂進展の抑制

概要

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The Stress Corrosion Cracking (SCC) has been observed in a component of low carbon austenitic stainless steel and in a weld of Ni based alloy in the domestic Boiling Water Reactors (BWRs) and in a weld of Ni based alloy in the Pressurized Water Reactors (PWRs). It is important for stable operation with a high level of safety to adequately perform preventive maintenance. Since the laser peening improves residual stress near the surface region by irradiating laser pulses in water, it has been applied for operating BWR and PWR plants as a preventive maintenance against the SCC. The residual stress in the weld region of core shroud support of BWR before and after the laser peening were examined by a finite element analysis. The magnitude of stress intensity factor (K) for a crack with an arbitrary depth is calculated by using the stress distribution. The results show that the K after the laser peening is not larger than that before (as-welded condition) and there is no ill effect on the crack propagation. It is also predicted that the laser peening effectively prevents the propagation of a small crack.
2008-08-25