Development of New Methodology for Distinguishing Local Pipe Wall Thinning in Nuclear Power Plants
ABSTRACT
To manage the wall thinning of carbon steel piping in nuclear power plants, the utility of Korea has performed thickness inspection for some quantity of pipe components during every refueling outage and determined whether repair or replacement after evaluating UT data. Generally used UT thickness data evaluation methods are Band, Blanket, and PTP (Point to Point) methods. Those may not desirable to identify wall thinning on local area caused by erosion. This is because the space between inspecting points of those methods are wide for covering full surface being inspected components. When the evaluation methods are applied to a certain pipe component, unnecessary re-inspection may also be generated even though wall thinning of components does not progress. In those cases, economical loss caused by repeated inspection and problems of maintaining the pipe integrity followed by decreasing the number of newly inspected components may be generated. EPRI (Electric Power Research Institute in USA) has suggested several statistical methods such as FRIEDMAN test method, ANOVA (Analysis of Variance) method, Monte Carlo method, and TPM (Total Point Method) to distinguish whether multiple inspecting components have been thinned or not. This paper presents the NAM (Near Area of Minimum) method developed by KEPCO-E & C for distinguishing whether multiple inspecting components have been thinned or not. In addition, this paper presents the analysis results for multiple inspecting ones over three times based on the NAM method compared with the other methods suggested by EPRI.
To manage the wall thinning of carbon steel piping in nuclear power plants, the utility of Korea has performed thickness inspection for some quantity of pipe components during every refueling outage and determined whether repair or replacement after evaluating UT data. Generally used UT thickness data evaluation methods are Band, Blanket, and PTP (Point to Point) methods. Those may not desirable to identify wall thinning on local area caused by erosion. This is because the space between inspecting points of those methods are wide for covering full surface being inspected components. When the evaluation methods are applied to a certain pipe component, unnecessary re-inspection may also be generated even though wall thinning of components does not progress. In those cases, economical loss caused by repeated inspection and problems of maintaining the pipe integrity followed by decreasing the number of newly inspected components may be generated. EPRI (Electric Power Research Institute in USA) has suggested several statistical methods such as FRIEDMAN test method, ANOVA (Analysis of Variance) method, Monte Carlo method, and TPM (Total Point Method) to distinguish whether multiple inspecting components have been thinned or not. This paper presents the NAM (Near Area of Minimum) method developed by KEPCO-E & C for distinguishing whether multiple inspecting components have been thinned or not. In addition, this paper presents the analysis results for multiple inspecting ones over three times based on the NAM method compared with the other methods suggested by EPRI.
Cite this paper
K. Hwang, H. Yun and C. Lee, "Development of New Methodology for Distinguishing Local Pipe Wall Thinning in Nuclear Power Plants," World Journal of Nuclear Science and Technology, Vol. 2 No. 4, 2012, pp. 192-199. doi: 10.4236/wjnst.2012.24030.
K. Hwang, H. Yun and C. Lee, "Development of New Methodology for Distinguishing Local Pipe Wall Thinning in Nuclear Power Plants," World Journal of Nuclear Science and Technology, Vol. 2 No. 4, 2012, pp. 192-199. doi: 10.4236/wjnst.2012.24030.
References
[1] J. Horowitz, “Recommendations for Controlling Cavitation, Flashing, Liquid Droplet Impingement Erosion, and Solid Particle Erosion in Nuclear Power Plant Piping Systems,” Electric Power Research Institute 1011231, Final Report, 2004. [2] N. A. Barton, “Erosion in elbows in hydrocarbon production systems: Review document,” Health & Safety Executive, TUV NEL Limited, Glasgow, 2003. [3] A. Machiels and D. Munson, “CHECWORKSTM Steam/Feedwater Application, Guidelines for Plant Modeling and Evaluation of Component Inspection Data,” Electric Power Research Institute 1009599, Final Report, 2004. [4] J. Horowitz, “Statistical Methods for the Analysis of Multiple-Inspection Flow-Accelerated Corrosion Data,” Electric Power Research Institute 1019175, Final Report, 2009. [5] D. G. Gusso, “Implementation Test Project on the Total Points Method,” Electric Power Research Institute 1022575, Technical Update, 2011. [6] J. Horowitz, “Least Squares Methods for Evaluation Inspection Data,” Electric Power Research Institute 1018456, Technical Update, 2008.
[1] J. Horowitz, “Recommendations for Controlling Cavitation, Flashing, Liquid Droplet Impingement Erosion, and Solid Particle Erosion in Nuclear Power Plant Piping Systems,” Electric Power Research Institute 1011231, Final Report, 2004. [2] N. A. Barton, “Erosion in elbows in hydrocarbon production systems: Review document,” Health & Safety Executive, TUV NEL Limited, Glasgow, 2003. [3] A. Machiels and D. Munson, “CHECWORKSTM Steam/Feedwater Application, Guidelines for Plant Modeling and Evaluation of Component Inspection Data,” Electric Power Research Institute 1009599, Final Report, 2004. [4] J. Horowitz, “Statistical Methods for the Analysis of Multiple-Inspection Flow-Accelerated Corrosion Data,” Electric Power Research Institute 1019175, Final Report, 2009. [5] D. G. Gusso, “Implementation Test Project on the Total Points Method,” Electric Power Research Institute 1022575, Technical Update, 2011. [6] J. Horowitz, “Least Squares Methods for Evaluation Inspection Data,” Electric Power Research Institute 1018456, Technical Update, 2008.