Application for authorization to build the Cigeo project 'GP2' - Operational safety. Report prepared in support of IRSN/2024-00167 notice of November 29, 2024

The French Nuclear Safety Authority (ASN) has asked the French Institute for Radiation Protection and Nuclear Safety (IRSN) for its opinion on the creation authorization application file (DDAC) for the Cigeo deep geological disposal project for high-level (HL) and long-lived intermediate-level (ILW) radioactive waste, submitted by the French National Agency for Radioactive Waste Management (Andra). This review follows on from several expert assessments carried out by IRSN since the 2005 Dossier, and in particular the review of the Safety options file (DOS) submitted by Andra in 2016. It is structured according to three thematic groupings: (i) the basic data retained for the safety assessment of Cigeo (GP1), (ii) the safety assessment in the operating phase of surface and underground facilities (GP2) and (iii) the safety assessment in the post-closure phase (GP3). This report concerns the GP2 group of topics, and follows on from the report on GP1, submitted in April 2024. IRSN underlines the significant progress made in demonstrating the safety of Cigeo in the operating phase, which has reached the level of maturity required at the DDAC stage for most of its components. However, this has not yet been demonstrated for the storage of bitumen-coated waste packages with regard to the risks associated with fire, or in terms of the control of the internal atmosphere in the HL cells, and to a lesser extent in the ILW cells during the closure phase, with regard to the risks of explosion. It is therefore important to consolidate and complete the assessment of Cigeo's safety in the operating phase, with a view to its commissioning, based in particular on demonstrators carried out in situ under industrial environmental and operating conditions. The industrial pilot phase, for which the work program has yet to be defined on the basis of consolidated objectives and success criteria, should enable the necessary elements to be gathered over the thirty years currently envisaged by Andra for this phase