Sealing of a geological repository for IL-LL and HL waste
The sealing of a geological repository for radioactive waste must ensure a major containment function over a very long period. To enable its experts to assess the safety files drawn up by Andra (1) as part of the CIGÉO project (2) IRSN is conducting active research on this topic, as shown by the VSEAL project, carried out in its underground research laboratory in Tournemire (Aveyron).
IRSN's research, in support of its expertise in the safety of geological disposal of Intermediate Level Long lived and high Level waste (IL-LL and HL waste), has four main objectives: -to characterize the level of containment of radioactive material by the geological medium (clay in the case of the CIGÉO project), -to understand the physicochemical interactions between the materials (concrete, steel, clay) and their effects on their properties, - to evaluate the hydromechanical behaviour of the seals (cell, shafts and ramps) and -to assess the monitoring strategy, which is a major issue including from a societal point of view.
This research mobilizes several approaches: numerical simulations, experiments in so-called surface laboratories and larger scale in situ tests in the heart of the clayey rock accessible in the IRSN underground research laboratory located in Tournemire (Aveyron).
It is within the framework of this last type of activity that the VSEAL research project on vertical seals is carried out. This one, by means of a 1 m diameter and 10 m deep drilling (3) equipped with about sixty sensors, aims to observe over a period of fifteen years the effects of incoming water and hydrogen that would be produced by the waste on the watertightness over time of a bentonite (4) seal, the material chosen to seal the CIGÉO facility, at the end of its operating period.
In addition to its engineering know-how, VSEAL illustrates IRSN's ability to translate scientific and technical questions, based on its expertise, into a research program that includes technological tests.
(1) National Agency for Radioactive Waste Management
(2) Deep geological disposal project for Intermediate Level Long-Lived and High Level Waste located in Bure (Meuse/Haute-Marne, France)
(3) A scale of 1/10 compared to that of the shafts planned for the CIGEO facility
(4) Variety of clay with significant swelling properties