Statistical analysis results of performance demonstration for piping welds

The Institute of Nuclear Energy Research in Taiwan has established an ultrasonic testing (UT) performance demonstration (PD) programme for the non-destructive testing crew in Taiwan's nuclear power plants. This programme is for qualifying personnel's manual detection skills on stainless steel piping and carbon steel piping welds. Artificial flaws embedded in welds comprise two types - circumferential and axial. Examinees are required to detect flaws and size flaw lengths. Statistical analyses, including accuracy rates, detection rates and relative sizing errors, are made over examinees' detection data. Based upon eighteen examinees' output in six PD sessions, the overall accuracy rate is about 90%, with stainless steel and carbon steel piping yielding similar results. The length sizing errors, however, depend on the piping material and flaw orientation. The statistical results can provide both regulatory authorities and utilities with a conservative evaluation of the confidence level of ealistic T esults n nuclear power plants.