ENIQ technical report: Link between risk-informed in-service inspection and inspection qualification

The report is the outcome of a project to investigate approaches to quantifying the confidence associated with inspection qualification. Two methods for quantifying the outcome from inspection qualification are described. The first method is a relatively simple process based on direct expert judgement. The second method is based on a more rigorous structured process employing Bayesian statistics, in which the subjective degree of belief in inspection capability derived from a Technical Justification (TJ) is expressed in probabilistic terms, and combined with data from practical trials results. Two pilot studies are described which involved a qualification body applying the quantification methods in practice. Guidelines were developed on how to relate inspection qualification results, risk reduction and inspection interval. Recommendations for further work to make the approaches developed more robust are provided.