Uranium-Series Disequilibrium Studies in Bedrock for the Safety Case of Deep Geological Disposal of Spent Fuel

摘要

The possibility of glacial meltwaters disturbing the stable conditions around a nuclear waste repository can be studied by the USD method. The method is based on the perception of uranium isotope mobilisation relative to~ 230Th occurring due to past meltwater intrusions. Uranium mobilisation occurs when redox potential increases. In shallow bedrock redox-potential may change under normal recharge. Similar changes probably occur when meltwater penetrates a deeper reducing aquifer. The role of redox conditions in U mobilisation appears dominant, as direct a recoil induced signals seem too weak to be observed for rock and water samples. The USD method can be used to provide support to the Finnish safety case in the area of complementary safety arguments and scenario formulations for transport calculations.