Deep geological repositories (DGR) count amongst the world largest environmental protection projects. They are the internationally advocated reference solution for the long-term management of high-level radioactive waste (HLW) and spent nuclear fuel (SNF). Many countries have engaged in programs to develop their own DGR. In Europe, four countries have passed the important milestone of choosing or announcing the appropriate site for the location of their HLW disposal facilities. Finland has almost finished the commissioning of its DGR and should start industrial disposal operations in 2025. Sweden has authorized the construction of its DGR and is finalizing the licensing document to start construction. France is reviewing the construction license application of its DGR. Switzerland has proposed the location of its DGR and is carrying out the production of the documentation for the license application. These four countries took decades to choose the location for their DGR. The length of this process is explained by 1) the amount of technical investigations and studies that were carried out to first identify, select and then fully characterize the suitable site and 2) the progressive decision-making process defined by their respective legal frameworks, including the participation and engagement of communities and stakeholders.

This article presents the crucial role played by the French underground research laboratory (URL) in initiating the deep geological repository project Cigéo. In January 2023, Andra finalized the license application for the initial construction of Cigéo. Depending on Government’s decision, the construction of Cigéo may be authorized around 2027. Cigéo is the result of a National program, launched in 1991, aiming to safely manage high-level and intermediate level long-lived radioactive wastes. This National program is based on four principles: 1) excellent science and technical knowledge, 2) safety and security as primary goals for waste management, 3) high requirements for environment protection, 4) transparent and openpublic exchanges preceding the democratic decisions and orientations by the Parliament. The research and development (R&D) activities carried out in the URL supported the design and the safety demonstration of the Cigéo project. Moreover, running the URL has provided an opportunity to gain practical experience with regard to the security of underground operations, assessment of environmental impacts, and involvement of the public in the preparation of decisions. The practices implemented have helped gradually build confidence in the Cigéo project.