Organization of the Independent Safety Review Done by Electrabel for the Safety Assessment of Doel 3 and Tihange 2 RPVs
The paper will deal with the way Electrabel carried out an independent control of the safety case studies of Doel 3 and Tihange 2 Reactor Pressure Vessels assessments after the discovery of indications of hydrogen induced flakes. Electrabel’s Physical Control Service (Service de Contrôle Physique: SCP), acting as an internal independent body, has been involved since the very beginning of the development of the Safety Case. Its objective has been to perform an independent review of the project deliverables issued by the Project Team. Several independent evaluations were carried out. Some were externalised: for instance Sandia National Laboratories performed calculations with an independent methodology to challenge the project grouping methodology; they also assessed the UT technique used for the non-destructive tests. Others were done internally: for instance, statistical calculations were performed during the UT qualification process, leading to a recommendation to increase the detection level. SCP also provided its recommendations when determining the fluence level for the irradiation campaigns done in the BR-2 reactor. This helped to challenge the correlations established for the Safety Case by the Project Team. The paper will detail the way the SCP was organised, the scope of its activities and reviews. It will detail the legal process of independent review as requested by the Belgian legal framework. It will also detail some specific actions carried out as the Sandia counter-study and some external expertise performed. During the whole assessment process, SCP produced several reports, synthetized in the final advise: ‘Report on independent analysis and advice regarding the Safety Case’ and its addendum, published on the website of the FANC. This late one covered the full project scope (Safety Case 2015 Version1), ranging from the preliminary studies, proceedings of mechanical tests, and draft documents up to the final justification file that was delivered to the Safety Authorities on 28 October 2015. An overview of those reports, the concerns and the solution found and finally the approbation of the action plan will be described. Nevertheless, the paper will not address the part of the review done by the Regulatory Body and its Technical Support Organization as it is out of the scope of the SCP activities.