A 6-step evaluation procedure based on the 3D computational fluid dynamics (CFD) code has been developed to evaluate local wall thinning due to flow-accelerated corrosion (FAC). As a result of verification and validation (V&V) evaluation of the 3D FAC code, it was confirmed that a wall thinning rate could be predicted with an accuracy of a factor of 2. One of the disadvantages of the 3D FAC code was that it required a lot of computational time and memory. In order to minimize computational time, a speedy and easy-to-handle FAC code based on 1D CFD analysis was developed. As a result of a V&V evaluation based on a comparison of calculated and measured wall thinning, it was confirmed that regional maximum wall thinning rates could be predicted with an accuracy within a factor of 2. Then it was applied for FAC risk evaluation for entire plant systems to point out the locations where future problems might occur and to prepare for continuous pipe inspections and early implementation of suitable countermeasures. For this purpose, not only the probability of serious wall thinning occurrence in the future but also a hazard scale of pipe rupture due to the serious wall thinning was analyzed. FAC risk was defined as the mathematical product of the possibility of serious wall thinning occurrence and its hazard scale.
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