Safety of the final disposal solution is based on the so-called multi-barrier principle, where several redundant engineered barriers ensure long-term safety.
The engineered barriers include the fuel state, final disposal canister, buffer bentonite and tunnel backfill. Bedrock serves as a natural barrier. Posiva has investigated and modelled all the details related to the engineered barriers.
The principle of nuclear waste management is to isolate radioactive waste from nature for so long as its radioactivity has fallen to an insignificant level.