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Vol.11 No.2previousAA157- SP20 (AA158-159-160-161-162) NT94

Academic Articles
Regular Paper Vol.11 No.2 (2019) p.65 - p.78
 

Evaluation of Capabilities on Ultrasonic Testing Examiners Using Probability of Defect Detection and Cumulative Failure Probability

 

Masayoshi KOJIMA1,*, Hideharu TAKAHASHI1 and Hiroshige KIKURA1

 
1 Tokyo Institute of Technology, 2-12-1-N1-7 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
 
Abstract
Ultrasonic testing (UT) is one of the non-destructive testing for pressure-retaining weld lines in class 1 piping of nuclear power plants. Since capabilities of UT examiners may affect failure risks of class 1 piping, UT is performed by certified examiners. In this paper, capabilities of uncertified and certified examiners were evaluated using probability of detection (POD) models and cumulative failure probabilities. The POD models is one of the input data of probabilistic fracture mechanics (PFM) analysis. Experimental data of blind testing for detecting stress corrosion cracking conducted by the uncertified and certified examiners were used for regression analysis of POD model. Two types of equation were selected for the POD model. Cumulative failure probabilities considering several inspection intervals were calculated in the PFM analysis. Then, the authors evaluated the failure risks of piping performed by the uncertified and certified examiners using the POD models and the cumulative failure probabilities. As a result, one equation of POD model with low residual sum of squares made it easier to evaluate the capabilities of UT examiners than the other POD model. Additionally, the equation with low residual sum of squares had less uncertainty on the failure risks of piping. Furthermore, it was shown that UT results performed by certified examiners might have equivalent failure risks of piping as UT results performed by uncertified examiners if an inspection interval gets longer.
 
Keywords
Failure Risk of Piping, Probability of Detection, Probabilistic Fracture Mechanics, Cumulative Failure Probability, Capabilities of Examiners, Ultrasonic Testing, Stress Corrosion Cracking, 95% Confidence Intervals
 
Full Paper: PDF EJAM Vol. 11 No. 2 pp.65-78 "Evaluation of Capabilities on Ultrasonic Testing Examiners Using Probability of Defect Detection and Cumulative Failure Probability"
Article Information
Article history:
Received 7 May 2019
Accepted 30 August 2019