A mock-up experiment was also installed at GTS in June 2010 as part of the FORGE project. Its purpose is to simulate the cavern seal of a L/ILW cavern (i.e. with a cement backfill of the emplacement cavern and a sand-bentonite seal) on an intermediate scale and under well controlled boundary conditions.

A steel cylinder (Fig. 1) is filled with a compacted sand/bentonite (S/B) seal (brown/yellow area in Fig. 1) and two porous mortar disks at both sides (grey areas). To prevent preferential water and gas flow along the interface between the S/B body and the steel cylinder the outer ring space was sealed with pure bentonite powder (yellow area).

As shown in the experiment schedule, the S/B mixture will first be saturated with water, followed by gas injection tests to assess gas migration behaviour at a decimetre scale. At the end of the testing, the experiment will be dismantled in order to analyse in detail the cement-clay interfaces.

Figure 1: Drawing of the mock-up experiment with the steel cylinder confining the experiment, mortar discs at moth ends (grey/brown), the S/B seal (brown/yellow), the pure bentonite (yellow) and the ring-TDRs (black). Instruments are schematically indicated to show the locations of the monitoring levels.

Experiment Schedule

Impressions from Emplacement:

Laboratory Column Experiments (FORGE)