Two key experiments in the “hot phase”

HotBENT – or why are we operating a heating system inside a mountain?

In our underground rock laboratory, the Grimsel Test Site, research is conducted under realistic conditions in the rock. The multinational HotBENT* Experiment helps to optimise deep geological repositories for radioactive waste.

We are investigating the impact of high temperatures on engineered barriers consisting of bentonite that will be used to backfill the drifts in which the disposal canisters will be emplaced. Four heaters are used to simulate the heat generated by the radioactive waste. The current temperature is 150 °C.

*High Temperature Effects on Bentonite Buffers (HotBENT)

Gas-Permeable Seal Test (GAST) – entering the main phase of the experiment

Due to the corrosion and degradation of radioactive waste (and construction materials), gas can form in the emplacement caverns of a deep geological repository for low- and intermediate-level waste.

Nagra has developed a system to increase the gas transport capacity of the underground structures without negatively impacting the ability to retain radioactive substances. The primary goal of the GAST project at the Grimsel Test Site is to test the functionality of this special sealing concept on a large scale and under realistic conditions.

To this end, the GAST project was installed at the Grimsel Test Site in 2011. After preparations were completed, the final phase of the experiment, the gas migration test, was started on 2nd May 2022. This phase will last around one and a half years.

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