Spent fuel elements in a deep geological repository radiate heat. The aim of the HotBENT experiment in the Grimsel rock laboratory is to investigate the temperature increase in a repository tunnel which is possible without damaging the artificial barrier system. In the repository concept, bentonite rings around waste containers are used as such safety barriers. The heat is simulated in the in-situ experiment with heating elements. Bentonite, a clay-like material intended for sealing the galleries, is investigated in this experiment.
If the temperature in the bentonite is too high, its function of safely isolating the waste might be reduced with a risk for the environment. The experiment demonstrates the temperatures, the bentonite can withstand, and shows the effects of a further temperature increase.
Contributions from Solexperts
- Instrumentation of the near-field with Solexperts multi-packer systems
- Hydrogeological exploration of the near field
- Hydration system of the bentonite
- Gas measurements
- Instrumentation of the experimental tunnel with oxygen electrodes and gas sampler for saturated and unsaturated conditions
- Gas circulation module with mass spectrometer to measure the gas composition both in the gas phase and in the liquid phase (i.e. the dissolved gases in the pore water) in the test gallery
- Instrumentation of the test gallery and the boreholes in the near field with partly heatable fibre optic cables for distributedsensing of temperature and thermal conductivity of the bentonite during the saturation phase