Considerations in Repairing the Thinned Piping in Nuclear Power Plants

Thinning due to flow assisted corrosion has been occurred in the carbon steel piping in the nuclear plants. The thinning should be systematically managed against the failure of the piping. The management includes the inspection, analysis and repair/replacement. Each of the activities has its own criteria for the safety class piping. But as for the non-safety class piping, there is no clear code requirement for the management for the thinning. The thinning management for the non-safety class piping depends on the plant owner's policy. This paper has investigated the current procedures, requirements and repair methods related with the thinned piping. Based on the investigation, the optimized repair methodology and its basis which can be applied to the non-class piping is proposed