A Bayesian Framework for the Quantitative Modelling of the ENIQ Methodology for NDT Qualification

Abstract

NDT inspection qualification according to the ENIQ methodology is a well established approach adopted by nuclear utilities in many European countries. According to the methodology, the inspection qualification is based on a combination of technical justification and practical trials, and it is thus qualitative in nature. For instance, the methodology does not give explicit guidance on how the evidence from the technical justification and results from trials should be weighted.

This paper describes how a quantification of the ENIQ qualification methodology can be achieved by means of Bayesian statistics. Such an approach offers, at least in principle, a structured method able to combine and quantify the “soft” evidence from a technical justification with the “hard” evidence obtained from practical trials. At the same time, our model offers an improved transparency in the qualification process, by giving explicit (and therefore auditable) “scores” to the subjective judgements made during the qualification exercise. A quantitative assessment of an NDT system capabilities would also be very useful for risk-informed in-service inspection applications, which are becoming more widely applied within the nuclear industry in Europe.