Geoscientific R&D for high level radioactive waste disposal in Sweden—current status and future plans

摘要

SKB (Svensk Karnbranslehantering AB) isresponsible for all handling, transport and storage of the nuclearwastes outside the Swedish nuclear power stations. A cording toSwedish law, SKB is responsible for a R&D-programme neededto take care of the radwastes. The programme comprises, amongothers, a general supportive geo-scientific R&D and the AspoHard Rock Laboratory (HRL) for more in-situ specific tasks.Sweden is geologically located in the Fennoscandian shieldwhich is dominated by genisses and granitoids of Precambrianage. The Swedish reference repository concept thus considers anexcavated vault at ca. 500m depth in crystalline rocks. In thisconcept (KBS-3), copper canisters with high level waste will highlevel waste will be emplaced in deposition holes from a system oftunnels. Blocks of highly compacted swelling bentonite clay areplaced in the holes leaving ample space for the canisters. At thefinal closure of the repository, the galleries are backfilled with amixture of sand and bentonite. This repository design aims tomake the disposal system as redundant as possible. Although theKBS-3 concept is the reference concept, alternative conceptsand/or repository lay-outs are also studied. The main alternative,currently under development at SKB, is disposal in boreholeswith depths of 4-5km. The geoscientific research will to a greatextent be guided by the demands posed by the performance andsafety assessments, as well as the constuctability issues. Somemain functions of the geological barrier are fundamental for thelong-term safety of a repository. These are : bedrock mechanicalstability, a chemically stable environment as well as a slow andstable groundwater flux. The main time-table for the finaldisposal of long-lived radioactive waste in Sweden foresees thefinal selection of the disposal system and site during thebeginning of next decade.