The aim of Lasgit is to perform a large scale gas injection test in a full-scale KBS-3 deposition hole.
The bentonite buffer is an important barrier in the KBS-3 system. The key purpose of the buffer is to serve as a diffusional barrier between the canister and the groundwater in the rock.
An important performance requirement on the buffer material is to not cause any harm to the other barriers.
Gas build up from corrosion of the iron insert could potentially affect the buffer performance in three ways:
- Permanent pathways in the buffer could form at gas break through. This could potentially lead to a loss of the diffusional barrier.
- If the buffer does not let the gas through, the pressure could lead to mechanical damage of the other barriers.
- The gas could de-hydrate the buffer.
The small scale experiments that have been performed over the last ten years demonstrate that effects according to items 1 and 3 above do not occur.
The current understanding of the gas transport process through compacted bentonite, also indicate that the buffer would open for gas passage before any harmful pressures are reached. However, there are still large uncertainties around the gas migration process and all these findings have to be verified in a large scale experiment.
Aspo Hard Rock Laboratory