Safety assessment and natural science research
The long-term safety of the repository is examined and evaluated by means of the safety assessment. At first, the initial state of the repository is described, after which possible long-term changes are explored. Finally, the consequences for man and the environment are described.
The safety assessment utilizes models that are developed in the research work and devises special modelling tools for integrated modelling. The repository's evolution is simulated by system models. Transport of released radionuclides is calculated using both numerical and analytical models.
The research is largely aimed at analyzing the long-term safety of a deep repository with spent fuel in terms of radiation-related, thermal, hydraulic, mechanical and chemical (including microbial) processes as well as radionuclide transport.
Research is also aimed at charting the changes to which the evolution of the biosphere and the climate give rise.
The fuel
The repository is supposed to isolate the spent fule. Research is made into the dissolution of the fuel if groundwater should enter via a breach in the canister. Leaching tests are also planned and calculations of decay heat and criticality.
The buffer
The buffer is supposed to protect the canisters and retard radionuclide transport. The state of the buffer after deposition has to be predicted. A number of processes are involved and the course of events is studied both in the field and with models. Studies are made into gas transport, colloid formation, erosion and interaction between buffer and canister.
The backfill
The backfill is supposed to stabilize the tunnel, keep the buffer in place and prevent water flow through the tunnels. Tests have been made into different concepts for tunnel backfilling and different clay-based materials. Processes that effect the swelling are important and studies will be made on the impact of freezing and erosion.
The geosphere
The geosphere protects the canisters and is a barrier to the escape and transport of radionuclides. Models to describe how the rock around the repository move are developed. Other models developed describe the movements of the groundwater in the rock and the chemistry of the groundwater. Studies of how microbes can affect conditions continue.
The biosphere
The biosphere is where we humans live and where releases from the deep repository would have consequences. Extensive research has been made into defining and describing the most important processes in different ecosystems and to predict changes that may take place in the future. The research has made it possible to device ecosystem-based models of the site in order to follow the path of radionuclides. New ways have been worked out, of calculating the radiation dose to man based on mass flows of water and organic carbon in the ecosystems.
The climate
It is important to determine possible climatic changes and how they may affect the long-term safety of the deep repository. Research has been made into shoreline displacement and development of permafrost and ice sheets and their affects on biosphere and geosphere.
(Sourse: RD&D-programme 2004 and RD&D-programme 2007)
For more information, please contact chief coordinatior Marcus Laaksoharju.
Visit SKB website and search among publications.
www.skb.se