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Environmental Fatigue Evaluation for Thermal Stratification Piping of Nuclear Power Plants

열성층을 포함하는 원자력발전소 배관의 환경피로평가

  • Received : 2018.09.05
  • Accepted : 2018.10.12
  • Published : 2018.10.31

Abstract

A detailed fatigue evaluation procedure was developed to mitigate the excessive conservativeness of the conventional environmental fatigue evaluation method for the pressurizer spray line elbow of domestic new nuclear power plants. The pressurizer spray line is made of austenitic stainless steel, which is relatively sensitive to the environmentally assisted fatigue, and has a low degree of design margin in terms of environmentally assisted fatigue due to the thermal stratification phenomenon on the pipe cross section as a whole or locally. In this study, to meet the environmental fatigue design requirements of the pressurizer spray line elbow, the new environmental fatigue evaluation has been performed, which used the ASME Code NB-3200-based detailed fatigue analysis and the environmental fatigue correction factor instead of the existing NB-3600 evaluation method. As a result, the design requirements for environmentally assisted fatigue were met in all parts of the pressurizer spray line elbow including the fatigue weakened zones by thermal stratification.

Keywords

environmental assisted fatigue;cumulative fatigue usage factor;spray line;fatigue evaluation;nuclear power plant