Aespoe Hard Rock Laboratory. Annual Report 2008

The Aespoe Hard Rock Laboratory (HRL) is an important part of SKB's work with the design and construction of a deep geological repository for the final disposal of spent nuclear fuel. The main activities in the geoscientific fields have been: (1) Geology - completion of the feasibility study concerning geological mapping techniques and mapping of rock surfaces in the new tunnel, (2) Hydrogeology - monitoring and storage of data in the computerised Hydro Monitoring System, (3) Geochemistry - sampling of groundwater in the yearly campaign and for specific experiments and (4) Rock Mechanics - field tests to evaluate the counterforce needed to prevent thermally-induced spalling in deposition holes. At Aespoe HRL, experiments are performed under the conditions that are expected to prevail at repository depth. The aim is to provide information about the long-term function of natural and repository barriers. Experiments are performed to develop and test methods and models for the description of groundwater flow, radionuclide migration, and chemical conditions at repository depth. The programme includes projects which aim to determine parameter values that are required as input to the conceptual and numerical models. A number of large-scale field experiments and supporting activities concerning Engineered barriers are carried out at Aespoe HRL. The experiments focus on different aspects of engineering technology and performance testing: The Prototype Repository is a demonstration of the integrated function of the repository and provides a full-scale reference for tests of predictive models concerning individual components as well as the complete repository system; The Long Term Test of Buffer Material (Lot-experiment) aims at validating models and hypotheses concerning physical properties in a bentonite buffer material and of related processes regarding microbiology, radionuclide transport, copper corrosion and gas transport; The objective of the project Alternative Buffer Materials is to study clay materials that in laboratory tests have shown to be conceivable buffer materials. Three test parcels with different combinations of clay materials are installed in boreholes at Aespoe HRL; The Backfill and Plug Test is a test of the hydraulic and mechanical function of different backfill materials, emplacement methods and a full-scale plug; The aim of the Canister Retrieval Test was to demonstrate readiness for recovering emplaced canisters even after the time when the surrounding bentonite buffer is fully saturated; The Temperature Buffer Test aims at improving our current understanding of the thermo-hydromechanical behaviour of buffers with a temperature around and above 100 deg C during the water saturation transient. The main goal of the project Sealing of Tunnel at Great Depth is to confirm that silica sol is a useful grout at the water pressures prevailing at repository level. To achieve this, the Tass-tunnel has been constructed at the -450 m level at Aespoe HRL. The objective of the project In situ Corrosion Testing of Miniature Canisters is to obtain a better understanding of the corrosion processes inside a failed canister. In Aespoe HRL in situ experiments are performed with miniature copper canisters with cast iron inserts. The Task Force on Engineered Barrier Systems addresses, in the first phase, two tasks: (1) THM processes and (2) gas migration in buffer material. However, at the end of 2006 it was decided to start a parallel Task Force that deals with geochemical processes in engineered barriers. During 2008, two Task Force meetings have been held. In Benchmark 1 (laboratory tests) the modelling of THM processes and gas breakthrough is finalised. In Benchmark 2 (large scale field tests) the main work has been within modelling of the Canister retrieval test at Aespoe HRL and the finalising of the modelling of the URL tests. Laboratory experiments and results from the experiment Long term test of buffer materials have been used as benchmarks for the performed geochemical modelling. In addition to SKB, eight organisations from seven countries participated in the international co-operation at Aespoe HRL during 2008. Six of them: Andra, BMWi, CRIEPI, JAEA, NWMO and Posiva together with SKB form the Aespoe International Joint Committee which is responsible for the co-ordination of the experimental work arising from the international participation. The international organisations are participating in the experimental work at Aespoe HRL as well as in the two Aespoe Task Forces: (1) Task Force on Modelling of Groundwater Flow and Transport of Solutes and (2) Task Force on Engineered Barrier Systems.