In situ radionuclide retardation in groundwater conducting systems; Overview of the research carried out at Nagra's Grimsel Test site, central Switzerland

Biggin, C.*; Mri, A.*; Alexander, W. R.*; Ota, Kunio; Frieg, B.*; Kickmaier, W.*; Mckinley, I. G.*

Environmental Radiochemical Analysis II, p.207 - 228, 2003/00

With increasing experience in the implementation of in-situ experiments, improved process understanding and more mature repository concepts, the experimental programmes at the Grimsel Test Site in Switzerland have gradually become more complex and more directly related to open questions defined by repository implementation organisations and regulatory bodies. To date, in situ radionuclide transport/retardation in fractured crystalline rocks have been studied, increasing in complexity from simple, non-sorbing to more chemically complex, strongly sorbing radionuclides. Currently, two ongoing in situ experiments at the GTS are investigating the in situ behaviour of radionuclides in the presence of clay colloids and the retardation of radionuclides under hyperalkaline conditions.