Challenges and Solutions to Localized Thinning Management of Secondary Loop Steam & Water Piping in Nuclear Power Plants

Engineering feed-backs and research results show that the secondary loop steam & water piping in light water reactor power plants, with the long-term operation of inner-fluid, may suffer from the following aging and degradation phenomena such as flow accelerated corrosion, liquid droplet impingement, cavitation erosion, etc., which may lead to the localized thinning of base metal or weld joint in the pipeline. Without predictive inspection and proactive aging management, the sensitive pipeline may experience local leakage, fracture or rupture. This paper briefly introduces above mentioned aging mechanism, aging effects, sensitive locations, affecting factors, as well as the management methods and practices at home and abroad. The art of status, application and development trend of pipe wall-thickness thinning inspection methods, inspection location, standardization are discussed in detail.