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RD&D-Programme 2004 - SKB

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Conclusions in RD&D 2001 and its review<br />

SKI points out that an essential issue that must be resolved before an application can be<br />

submitted for a permit to build the final repository is the ultimate choice of a suitable backfill<br />

material, particularly the clay component.<br />

Kasam points out that materials with different properties may be needed in different chambers.<br />

Newfound knowledge since RD&D 2001<br />

See section 18.2.2.<br />

<strong>Programme</strong><br />

See section 18.2.2.<br />

18.1.7 Water content<br />

The initial water content in the backfill follows trivially from its material specifications. It is a<br />

parameter that can be checked when the material is mixed.<br />

18.1.8 Gas contents<br />

The initial gas content in the backfill follows trivially from its specifications.<br />

18.1.9 Hydrovariables<br />

The hydrovariables are water flow, water pressure, gas flow and gas pressure. Initially it is<br />

relevant to describe gas and water pressure. Flows do not occur initially in the backfill. At<br />

emplacement, the repository will be open to atmospheric pressure. This gives a gas pressure<br />

(air) of 1 atm (approx. 0.1 MPa) and a water pressure of 0–0.1 MPa in the surrounding host<br />

rock. On the other hand, as in the buffer there will be an initial negative pore water pressure<br />

in the unsaturated backfill, which drives the inward transport of water along with the positive<br />

pressure from the water in the rock. This negative pore pressure is dependent on which concept<br />

is chosen.<br />

18.1.10 Swelling pressure<br />

The swelling pressure begins to build up when buffer and backfill come into contact with<br />

external water. Initially there is no swelling pressure.<br />

18.1.11 Smectite composition<br />

At present there are several alternative backfill concepts and backfill materials, see section<br />

18.1.6. In some of the concepts the clay portion consists of the same material as the buffer,<br />

see section 17.1.2, and in other concepts of a completely different material, for example<br />

Friedland clay.<br />

Conclusions in RD&D 2001 and its review<br />

See section 18.1.6.<br />

Newfound knowledge since RD&D 2001<br />

See section 18.2.2.<br />

RD&D-<strong>Programme</strong> <strong>2004</strong> 229

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