The objectives and scope of the technical and safety options report for assessing the feasibility of shallow disposal on the Communauté of Communes of Vendeuvre-Soulaines (CCVS) site (France, dep. 10)

Background to the studies carried out to prepare the report

France currently has solutions for the disposal of VLL and LIL-SL radioactive waste, with surface disposal in operation, and a deep geological disposal solution (Cigéo facility project) is currently under study for IL-LL and HL waste. For LL-LL waste, which represents volumes of over 200,000 m³, Andra has been studying a shallow depth disposal solution in a clay formation for several years.

In France, shallow depth disposal is considered to be the most appropriate solution for the disposal of LL-LL wastes, proportionate to their hazardous nature. In 2013, Andra identified a site with geological characteristics suitable for hosting such a repository (outcropping clay formation), on which geological investigations were carried out. The site is located to the north of the Vendeuvre-Soulaines community of communes (CCVS) in the Aube department (10).

Since, Andra has been conducting studies to design a shallow-depth disposal on this site, which would constitute one of the solutions to manage a part of LL-LL waste. Andra has constituted a report submitted to the French government in March 2024, presenting the studies carried out, the results obtained and the lessons learned regarding the technical feasibility and post-closure safety of a shallow depth disposal in clay formation for waste candidates.

Objectives and scope of the studies

At this early stage of the project's development, Andra has focused its safety studies on the post-closure period including large time scales (over 50 000 years), taking also into account the current environmental issues, constructional and geological aspects of the CCVS site.

To this end, Andra has established a post-closure safety approach for a shallow depth disposal beyond 50,000 years, and applied it to the CCVS site for LLW-LL, in order to assess the radiological impact of the repository on large time scales using a conservative approach. The effects of erosion on the study area over these long time scales were also studied to assess the loss of cover thickness that could occur, with the aim of justifying the 30 m depth at the top of the storage cells to isolate the waste from man and the environment on long enough time scales. To do this, Andra has taken into account the climatic changes that may occur in the very long term, in order to provide a framework for the site's geodynamic evolution. These assessments led to evaluate the waste’s compatibility with a shallow depth disposal and the site's capacity

The Andra’s studies have established the feasibility of shallow depth disposal on this site, for some of the waste studied. In particular, the assessments carried out had clarified the main phenomenological and design determinants driving post-closure performance and safety indicators. These studies have also shed light on the characteristics of a site suitable for the disposal of LL-LL wastes that are not eligible to be disposed of on the CCVS site.