The Waste Advisory Committee’s recommendations on the long-term safety of Cigéo

  • Environment

  • Information bulletin

28/08/2025

The Advisory Committee for Waste issues its recommendations on the long-term safety of Cigéo in the post-closure phase and formulates its general conclusion

At the end of the technical review phase of the Cigéo project construction licence application, ASNR presented its 3rd expert report to the Advisory Committee for Waste, which issued its recommendations on the long-term safety of Cigéo in the post-closure phase and its general conclusions on the application file.

  • The third and final phase of the technical review of the Cigéo project construction licence application was concluded with the meeting of the Advisory Committee for Waste (GPD) on 25 and 26 June 2025. This third phase focused on the safety of Cigéo in the post-closure phase. The discussions of the GPD were based on the expert review conducted by ASNR's Division of Environment.
  • The GPD considered that the demonstration of post-closure safety presented by Andra was satisfactory for this stage in the project development, taking into account the commitments made by Andra and subject to the observations it made at the end of its review being taken into account. It considers that the disposal system, in the chosen architecture, has a good overall containment capacity and is robust with regard to all of the post-closure risks and uncertainties studied.
  • Having examined the entire application file submitted by Andra, the Advisory Committee for Waste considers that the safety demonstration for Cigéo is based on a solid knowledge base and has reached the level of maturity required at this stage. Nevertheless, it raised some important issues that require further consideration and will need to be evaluated at future milestones in the project development.
  • ASNR will issue its opinion on the Cigéo project construction licence application in accordance with Article L. 542-10-1 of the Environment Code with a view to informing the public about this application in advance of the public inquiry. In this opinion, which is due to be issued in mid-November 2025, ASNR will present, on the basis of its own expert review and the recommendations of the GPD, the elements it deems necessary to complete the safety demonstration with a view to updating the file in advance of the public inquiry, as well as those elements required for the later stages of development of the Cigéo project.
  • The stakeholders involved in the various dialogue processes run by ASNR during the technical expert review and instruction phase will be consulted in the autumn as part of the preparation of this opinion in order to ensure the continued participation of civil society in ASNR's referral, review and instruction phases and to enable them to play their full role with a view to future regulatory consultations, in particular the public inquiry scheduled for 2026.

Specific consultation of stakeholders on ASNR's draft opinion: ASNR will present its draft opinion to the stakeholders involved in the technical instruction at a meeting in early October. Following a comments and questions phase, ASNR will organise a workshop in November to share the contributions received, which it will take into account when finalising its opinion.

On 16 January 2023, Andra submitted to the Ministry of Ecological Transition its construction licence application (DAC) to build a deep geological radioactive waste disposal facility, known as Cigéo. ASN received a referral request from the Ministry of Ecological Transition in March 2023 to lead the technical instruction of this application.

ASN requested that the technical review of the application file be divided into three thematic groups: the basic data used for the safety assessment of Cigéo; safety during the operational phase of the surface and underground facilities; and post-closure safety. Cross-cutting themes are also being studied, such as reversibility (including the principle of disposal adaptability, radioactive waste package recoverability and verification of the absence of negative impacts on post-closure safety), the pilot industrial phase and the consequences of climate change. The first phase ended with a meeting of the Advisory Committee for Waste (GPD) on 24 and 25 April 2024 and the second phase with a meeting on 10 and 11 December 2024.

The Division of Environment of ASNR presented its technical review and the Advisory Committee for Waste (GPD), meeting on 25 and 26 June 2025, examined the third thematic group with the support of members of the Advisory Expert Committee for Laboratories and Plants (GPU) and for Radiation Protection for workers, the general public, patients and the environment (GPRP), and then issued its general conclusions after examining the full file submitted by Andra.

A technical dialogue was organised by the National Association of Local Information Committees and Commissions (ANCCLI), the Local Committee for Information and Follow-up of the Bure Laboratory (CLIS de Bure) and ASNR during the technical review of the Cigéo project construction licence application file (DDAC). This dialogue started in early 2023 and will finish in early October 2025. The objectives are to take account of the concerns and questions of civil society in order to make ASNR's technical review more robust and to enable civil society to form its own opinion on nuclear safety and radiation protection issues and therefore participate in the process leading up to the public decision.

At the same time, ASNR conducted a consultation on the draft global referral to IRSN and on the draft referrals to the Advisory Committee for Waste in order to gather the opinions of stakeholders who are members of the working group on the French National Radioactive Material and Waste Management Plan (PNGMDR working group).

With regard to the examination of the third thematic group on the post-closure safety of Cigéo, the following conclusions were highlighted by the technical review conducted by ASNR's Division of Environment.

The demonstration of the post-closure safety of Cigéo has reached the level of maturity required at the current stage of the disposal facility construction licence application (DAC). The relevance of the approach adopted by Andra to assess the post-closure safety of Cigéo was emphasised. This approach is based on the examination of its containment performance via disposal evolution scenarios that have been deduced from an overall satisfactory analysis of the long-term risks and uncertainties associated with the performance of its components.

The assessment of the normal evolution scenario (NES), which corresponds to the foreseeable evolution of the facility and the geological environment, points to the good containment capacity of the disposal system. However, further efforts to consolidate knowledge, particularly knowledge of the solubility of selenium and the hydraulic properties of the Callovo-Oxfordian (COx) geological formation, are still needed to establish margins in relation to the radiation protection objectives.

The scenarios covering the malfunction of seals or HLW disposal containers and the collapse of a cell during the operational phase, which lead to degraded containment performance, result in health impacts at the same level as for the NES. These impacts may nevertheless be greater for the scenarios involving an undetected fault in the ILW-LL disposal zone or inadvertent human intrusion, without them being unacceptable in view of the very low probability of the scenarios used and the severity of their underlying assumptions. It was noted that, in response to societal demand, Andra had agreed to take into consideration a scenario under which the disposal facility was abandoned before closure, with the aim of identifying, where appropriate, arrangements for early closure of the disposal facility designed to limit the consequences for long-term safety; this was considered satisfactory in view of the planned centuries-long operation of the facility.

Taking all these factors into account, the disposal system, in the chosen architecture, appears to be robust in respect of the risks and uncertainties linked to its evolution. The assessments of the radiological and chemical impacts on the environment and the chemical impacts on health point to very low impacts.

However, in the absence of a substantiated comparison of several architecture options with regard to safety-related criteria during the operational phase and after closure of the facility (as already highlighted by ASN at the end of the DOS expert assessment), ASNR’s Division of Environment was not in a position to comment on whether the disposal architecture chosen at the DDAC stage had been optimised, without prejudging however that it is not the case. From the point of view of post-closure safety, this architecture places an additional burden on the drift seals by not taking advantage of the proven gain linked to the positioning of the ILW-LL disposal zone hydraulically downstream of the surface-to-underground links. In this regard, the number, location and performance of the drift seals in the chosen architecture still require justification.

Regarding memory management, the preparatory work undertaken by Andra is considered satisfactory at the current stage of the development of the project and should be continued.

Lastly, while no prohibitive factor relating to safety following the closure of the disposal facility housing waste from the reserve inventory have been identified at this stage of the adaptability studies, substantial efforts are still required to demonstrate that the disposal of spent fuel (SF) does not pose a long-term criticality risk once maintaining their shape can no longer be guaranteed.

At its meeting on 25 and 26 June 2025, the Advisory Committee for Waste (GPD) confirmed the main conclusions of the technical review conducted by ASNR's Division of Environment, particularly the good overall containment capacity and robustness of the disposal system in the chosen architecture. However, the GPD did emphasise the need to assess the level of conservatism of the safety assessment in relation to the radiological protection objectives in the envelope situation entailing an abandoned borehole in the area of the disposal facility. With regard to management of the criticality risk associated with disposal of the reference inventory, the GPD also considers that the information presented by Andra suggests that there is no post-closure criticality risk for the reference inventory. However, the GPD points out that while exclusion of the criticality risk is satisfactory in principle, it could be difficult to demonstrate given the time scales involved. Lastly, with regard to optimising the operational and post-closure safety of the currently chosen architecture, the GPD notes that Andra has studied the impact of the length of the drifts on possible containment performance gains, but has not responded to all aspects of the request made by ASN in this regard at the end of the DOS review. The GPD therefore considers that Andra should complete its application file with a justification of the positioning of the ILW-LL disposal zone in relation to the surface-to-underground links and of the number and location of the drift seals in the chosen architecture.

As a general conclusion, ASNR's Division of Environment and the Advisory Committee for Waste (GPD) emphasised the significant progress made in the Cigéo safety demonstration since the DOS (safety options dossier) stage, both in terms of consolidating the underlying knowledge base and assessing the operational and post-closure phases. Overall, this demonstration has reached the level of maturity required at this stage for the chosen architecture and now needs to be completed and consolidated. In this respect, it is worthwhile recalling the specific time frame for the Cigéo project, which includes a pilot industrial phase lasting an estimated thirty years from the date of issue of the construction licence decree. During this phase, which is intended to establish the safety demonstration for the disposal facility on the basis of studies and tests carried out in its geological environment and under conditions representative of its industrial operation, the complements and consolidations identified as necessary following the expert assessment of the DDAC should be discussed at assessment appointments prior to the commissioning of the facility, which is currently planned by Andra for 2050, e.g., upon reaching key technical milestones such as the start of excavation works or the start of construction of the first cell, etc.

In particular, any complements likely to lead to design changes, such as consolidating knowledge of the properties of the host rock above the deep structures detected below the northern part of the HLW disposal zone; changes to compartmentalisation and emergency response measures in the event of fire; demonstration of the safe operation of the HLW cells and closure of the ILW-LL cells; and monitoring measures, will have to be assessed prior to excavation of the concerned structures. Additional information about the sealing structures is needed in advance of assessment appointments to be held during the pilot industrial phase. The conditions for the disposal of bituminous waste require further examination. These complements will have to be taken into account when drawing up the programme for the industrial pilot phase, the objectives and success criteria of which are still provisional at this stage.

Finally, the flexibility of the facility is fundamental to guaranteeing the safe management of all the waste in the reference inventory, including in the event of changes to the architecture or design of the facility considered at the DAC stage. With regard to the adaptability of Cigéo in respect of waste from the reserve inventory, no prohibitive issue linked to the safety of disposal of SF and LLW-LL waste has been identified at this stage of the studies. In the event of plans to dispose of waste other than waste from the reference inventory, an additional safety demonstration would be required.

The various assessment appointments called for in the expert assessment of the application file are to be governed by technical requirements that ASNR may issue for the purpose of implementation of the construction licence decree. Where necessary, these appointments will give rise to dialogue with stakeholders and the public in order to strengthen public participation throughout the life cycle of the facility, as required by law.

Read more

Safety of Cigéo in the operational phase (December 2024)

Evaluation of the basic data adopted for the Safety Assessment (April 2024)