Gas and water transport from the WP-Cave repository

Gas and water transport from the WP-Cave repository has been calculated. The gas production has been estimated to be in the interval 3500 to 74000 Nm3/y. The water flow during the initial period will occur with a maximum overpressure in the interior of the repository of 0.75 MPa. The gas flow requires an initial high overpressure. The gas flow through the bentonite-sand barrier starts only if the overpressure is greater than the critical pressure. The critical pressure for a mixture bentonite-sand 50/50 is about 0.5-1.5 MPa. An alternative design is discussed, the use of a mixture bentonite-sand with a lower content of bentonite (e.g. 10/90). In this case the critical pressure is lower and the pressure needed to maintain a given flow is lower as well. (authors)