We studied how crushed salt changes over time so it can safely seal a future waste repository. By combining new laboratory tests with improved computer models, we created a clearer picture of how the material compacts and when it becomes tight. Our results reduce uncertainty in long‑term predictions and support safer planning for storing radioactive waste underground.

Knowledge of how gas moves through clay-rich rocks and barrier systems in a radioactive waste disposal facility is important to give confidence to long-term containment of waste. The GT experiment was designed to determine the physics driving gas movement in Opalinus Clay, the candidate host rock in Switzerland. The way gas moved through the rock was seen to change based on the rate of gas pressurisation rate – by analogy, the rate of gas production in a geological disposal facility.