SIMULATION OF RADIONUCLIDE RELEASE FROM A REPOSITORY TO THE BIOSPHERE- USING A MODEL-COUPLING CONCEPT

The release from initially damaged canisters for spent fuel located in crystalline rock is calculated. The radionuclide transport through th e nearfield is calculated using the compartment model (NUCTRAN), and t hen the channel network concept (CHAN3D) is used for the transport in the farfield. The flow rates at certain canister locations from the fl ow field generated by CHAN3D are used as input data to NUCTRAN, and th en the near-field release is used as input to the far-field transport simulations. The models are applied to a hypothetical repository layou t located at the Swedish Aspo Hard Rock Laboratory site. The hydraulic data and the flow-wetted surface area used in the model are estimated from hydraulic measurements. Release rate calculations for several ra dionuclides are performed to illustrate the model-coupling concept. Th e coupled models can be used as an efficient tool to simulate release from a repository and the transport to a recipient.