抄録
Wall thinning of carbon steel pipe components due to Flow-Accelerated Corrosion (FAC) is one of the most serious problems to the integrity of steam cycle piping system in Nuclear Power Plants (NPP). If the thickness of a pipe component is reduced below the critical level, it cannot sustain pressure and consequently results in leakage or rupture. For this reason, wall thinning by FAC has been inspected in secondary side piping systems in NPPs. The objective of this research is to verify confidence of wall thinning measurement system by conducting Round Robin Test (RRT). 12 inspectors from 3 companies participated and, 23 specimens by size and shape were used according to standard practice in RRT. Generally measurement system errors consist of repeatability and reproducibility. Repeatability is the variability of the measurements obtained by one person while measuring the same part repeatedly. In addition, reproducibility is the variability of the measurement system caused by differences in operator behavior. The gage R&R analysis was introduced for each sigma quality level, so that repeatability and reproducibility can be estimated from RRT results. In addition, bias and linearity are analyzed from RRT results. From this analysis, confidence intervals of thickness measurement system were obtained.
