Results of the Pilot Study on the Quantitative Modelling of the ENIQ Methodology for NDT Qualification

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 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 the results of a pilot study which included a Bayesian model that combines and quantifies the "soft" evidence from a technical justification with the "hard" evidence obtained from practical trials. It was applied to a realistic Qualification Dossier by experienced NDT qualification specialists. The Bayesian approach offers a structured and improved transparency in the qualification process, by giving explicit "scores" to the subjective judgements made during the qualification exercise. Further, a quantitative assessment of the capabilities of a NDT system can be very useful for risk-informed in-service inspection applications, which are becoming ever more widely applied within the nuclear industry in Europe.