Nuclear Waste: The Second Phase of Technical Review for Cigéo is Complete

The second phase of the technical review of the creation authorization application (DAC) for Cigéo was completed at the end of 2024. On this occasion, the French Nuclear Society (Sfen) spoke with Marine Levieux, DAC review lead at the French National Agency for Radioactive Waste Management (Andra), to assess the progress of this second milestone.

The creation authorization application for Cigéo, the future deep storage site for France’s most radioactive nuclear waste, was submitted to the Nuclear Safety and Radiation Protection Authority (ASNR) in January 2023. After validating the first instruction phase in June 2024, the French National Agency for Radioactive Waste Management (Andra) has now completed the second phase, which focused on “safety during the operational phase of surface and underground facilities.” As was the case for the previous phase, the Permanent Group of Experts for Waste (GPD) issued an opinion based on the assessment conducted by the Institute for Radiation Protection and Nuclear Safety (IRSN) on this second stage of the dossier. It was therefore demonstrated that “the operational safety of the surface facilities and the underground infrastructure presented by Andra is generally satisfactory at this stage of the project.” The third and final phase is already under review and is expected to be completed by June 2025.

What additional studies are expected regarding the risk of explosion?

Explosion risks exist on two distinct levels: one concerns MA-VL waste (medium-level, long-lived waste) [1], while the other pertains to HA waste (high-level waste) [2]. Regarding MA-VL waste, at this stage of the review process within the framework of operational safety, the IRSN considers that the risk is being managed satisfactorily. Studies are already planned in the coming years to improve the management of explosion risk during the closure phase. Concerning HA waste, the current safety demonstration is based on achieving an environment with 1% oxygen, thereby preventing explosion risks. At this stage, the IRSN does not challenge this approach but expects a more in-depth demonstration of its feasibility. A test program, closely resembling a realistic configuration, is therefore planned and will help validate the elements provided for the DAC.

And what about the risk of fires?

First and foremost, the IRSN has determined that fire risk management, in terms of prevention measures, consequence mitigation, and monitoring, is satisfactory. Our approach is primarily focused on prevention, particularly on limiting heat loads to ensure that all possible measures are taken to prevent a fire. However, there are several requirements that will necessitate additional evidence at a later stage. One key aspect relates to fire compartmentalization. Andra has, for example, chosen not to compartmentalize the access ramps, which are very long, to manage a fire. The IRSN does not challenge this decision but requests further justification to confirm that it is the appropriate choice. Additionally, further studies are expected regarding the intervention times required for specialized teams to extinguish a fire at great depths.

Conceptual 3D rendering of the Cigéo storage site

What does Cigéo’s adaptability to the reserve inventory entail?

The safety demonstration of Cigéo is based both on a reference inventory and on adaptability to a reserve inventory. The reference inventory includes all waste from nuclear facilities that have already received authorization. The reserve inventory, on the other hand, accounts for uncertainties, particularly those related to the implementation of new waste management sectors (FA-VL) or changes in energy policies, such as the storage of spent fuel in the event of a halt to reprocessing. In this context, Andra has also incorporated into the DAC review process the waste resulting from the extension of nuclear facility lifetimes as well as waste from the six future EPR2 reactors.

What are your expectations for the final phase?

So far, we are satisfied with the progress of the review process. Initially, the results of GP1 (the first group of topics evaluated in the DAC review process) were deemed mature and robust, allowing the review to continue with the evaluation of operational safety. This second phase was also deemed satisfactory at the expected level for a DAC. However, certain additional aspects still need to be refined. These have been formalized as commitments integrated into various milestones within the Cigéo project timeline. Regarding the final phase on post-closure safety evaluation, we also expect a demonstration that is sufficient at the DAC stage and that provides the final elements proving that the Cigéo geological storage project meets its primary objective: to store the most radioactive waste with the expected level of safety over the long term. ■