Determination of Vulnerable areas to Flow-Accelerated Corrosion Utilizing Risk Based Inspection Concepts

Accelerated flow (Flow Accelerated Corrosion), with the destruction of the protective layer of oxide on the surface of the tube and carbon steel tanks, causes corrosion in the plant piping system. Unlike many of corrosion leading to failure, no break until complete rupture of the pipe and corresponding tank, in pipeline does not appear. Therefore, the occurrence of this phenomenon, if not detected on time and does not prevent its progression, lead to the failure of main feedwater pipeline to steam generator in nuclear power plant. Since the failure of the main feedwater pipeline is among the events that could cause damage to the reactor core, detecting and correcting supervisory activities to prevent the FAC phenomena is inevitable and vital. On the other hand, the nature of the break before leakage of exposed pipeline to FAC, and technical barriers and cost issues in the context of the implementation of inspections, has led to the complexity and the diversity in their implementation. In this study, we present a method to determine the candidate points to carry out Risk-Based Inspection (RBI) and a brief description of the different methods of inspection. Furthermore, performance and benefits of pulsed eddy current method (Pulsed Eddy Current),to detect corrosion caused by FAC in main feedwater pipeline to steam generator, has been explained. This technique measure the corrosion caused by the FAC based on measuring the wall thickness of the pipes. The effective implementation of this method, in addition to increase efficiency and reduce the cost of doing RBI, reduce the frequency of failure of the pipeline in vulnerable areas to FAC and core damage frequency of nuclear power plants.

Keywords:

Flow Accelerated Corrosion , Risk Based Inspection , Feedwater System , Risk Matrix