국내 안전등급 배관에 대한 손상사례 분석

The purpose of this paper is to analyze piping failure trend of safety pipings in domestic nuclear power plants. First. database for the piping failure was constructed with 105 data fields. The database includes plant population data. event data. and service history data. 7 kinds of piping failures in domestic NPPs were investigated. Among the 7 cases. detailed root causes were investigated for 3 cases. The first one is pipe wall thinning in main feedwater pipings of Westinghouse 3 loop type plants. The root cause of the wall thinning was flow accelerated corrosion near welding area. The next one is leak event in chemical and volume control system(CVCS) due to vibration. Some cracks occurred in socket welding area. The events showed that the integrity of socket weld is very vulnerable to vibration. The last one is also a leak event in primary sampling line in Korean standard reactor due to thermal fatigue. Although the structural integrity was not maintained by the events. there was no effect on nuclear safety ill the above 3 piping failure eases.