Approach to Uncertainty Estimation in Ultrasonic Testing Results in the Field of Nuclear Energy

Abstract Ultrasonic testing (UT) is a fundamental nondestructive method used for defect detection and sizing in safety-critical components, particularly in the nuclear energy sector. Despite significant advancements in the accuracy of UT result evaluation across various techniques, the results remain strongly influenced by measurement conditions, human factors, and the applied evaluation methodology. To increase the credibility and interpretability of the ultrasonic data, one of the options is to report the measurement uncertainty associated with values determined by defect sizing. This paper presents the outcomes of the research project TAČR TK04010018, conducted by CVŘ and ÚJV between 2022 and 2025, focused on developing a methodology for determining and expressing the uncertainty of ultrasonic testing results. The evaluation concentrated on the accuracy of defect sizing using pulse-echo and phased array techniques. A comprehensive experimental program generated tens of thousands of values, which were statistically analyzed to determine type A uncertainties based on testing parameters. The results showed that uncertainty can be meaningfully quantified only for specific defects with defined parameters, and that a tiered approach is essential for determining and expressing uncertainty of UT results, enabling practical application depending on the required level of testing accuracy. A significant influence on the accuracy of ultrasonic testing results is exerted by type B uncertainties, which are affected by individual judgment and method-specific assumptions. The findings improve UT accuracy and reliability and indicate the need for further research.