Laboratory Column Experiments (FORGE) - Introduction
The Swiss Low-Intermediate Level Waste (L/ILW) repository concept foresees cavern plugs and a repository seal to prevent excess gas pressures in the repository. The main aim of the plugs and the seal is to increase the gas transport capacity of the backfilled underground structures without compromising the radionuclide retention capacity of the engineered barrier system (NTB08-07). The design option is called "engineered gas transport system (EGTS)" (Fig. 1). It involves specially designed backfill and sealing materials such as high porosity mortars as backfill materials for the emplacement caverns and sand/bentonite (S/B) mixtures with a bentonite content of 20 – 30 % for backfilling other underground structures and for the seals.
Schematic display of the Swiss Low-Intermediate Level Waste (L/ILW) Repository concept with potential gas release pathways indicated with red arrows
As seen in Figure 1, there are different potential gas pathways that may or may not develop due to gas production in the repository after closure, namely:
- Gas flow along the EDZ
- Gas flow through the plugs and the seal
- Gas flow into the host rock
Laboratory Column Experiments (FORGE)