Circumferential Weld Root Flow-accelerated Corrosion and Inspection of Secondary Loop Steam & Water Piping in Nuclear Power Plants

The industry should pay more attention to the secondary loop steam and water pipeline circumferential weld root flow-accelerated corrosion (FAC) in nuclear power plants. Without effective inspection and supervision, it will lead to high energy pipe leakage or rupture. The related field feedbacks, weld root FAC and its affected factors were discussed in detail. The advantages and disadvantages of different wall-thickness inspection methods are introduced and the weld root ultrasonic time of flight diffraction(TOFD) inspection principle and testing results were discussed in detail. It was shown that the difference of contents chromium in weld and adjacent base metals will significantly affect the flow-accelerated corrosion locations in carbon and low-alloy steel water and steam pipelines. Furthermore, TOFD can be applied to inspect local wall-thinning caused by flow-accelerated corrosion at circumferential weld joint roots of secondary loop steam & water piping in nuclear power plants.