HotBENT Experiment

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



Jocelyn Gisiger

Geologist ETHZ

Hydrogeological instrumentation and tests

T 0041 44 806 29 89

Karam Kontar

Engineering Geologist
Hydrogeologist CHYN

Member of the extended executive board
Division Manager Hydrogeology / Hydrogeological instrumentation and tests / Hydro-tests in shallow and deep boreholes

T 0041 44 806 29 85

Axel Fabritius


Member of the extended executive board
Branch manager Solexperts GmbH Karlsruhe
Thermal leak detection / Temperature measurements

T 0049 721 600 20