HR: 1340h
AN: H43F-0417    [Abstracts]
TI: Investigations of the Effective Diffusivity in the Oskarshamn Site Investigation Area
AU: * Lofgren, M
EM: martinl@ket.kth.se
AF: Department of Chemcial Engineering and Technology, Royal Institute of Technology, Stockholm, SE-10044 Sweden
AU: Neretnieks, I
EM: niquel@ket.kth.se
AF: Department of Chemcial Engineering and Technology, Royal Institute of Technology, Stockholm, SE-10044 Sweden
AB: At present two sites in Sweden undergo site investigations for a deep geological repository for spent nuclear fuel. This paper present results concerning the effective diffusivity of the rock at repository depth in the Oskarshamn site investigation area. The geology of this site is dominated by granite, granodiorite and diorite. In a campaign, the effective diffusivity of the rock surrounding the 1000-meter deep boreholes KSH01A and KSH02 was investigated. The effective diffusivity is one of the most important parameters for radionuclide retention and strongly affects the performance of the geosphere as a natural barrier. The effective diffusivity was investigated in the laboratory on 83 samples, taken from the bore core of KSH01A and KSH02, by an electrical resistivity method. Formation factors ranging from $2.2 \times 10^{-7}$ to $9.0 \times 10^{-4}$ were obtained. The effective diffusivity was also investigated in-situ by formation factor logging using the electrical resistivity method. A total of 1867 in-situ formation factors were obtained that corresponded well with the formation factors obtained in the laboratory with a few exceptions. As such a great number of formation factors was obtained, formation factor distributions for specific rock types can be presented. The results suggest that the formation factor may be distributed according to the log-normal distribution. The results of this campaign show that the porosities and effective diffusivities used in the Swedish SR-97 safety assessment may have to be somewhat reassessed. The used of a single effective diffusivity value in a safety assessment could be questioned, as the obtained formation factors ranged over at least 3 orders of magnitude. In fact, at this site the traditional concept of the formation factor could be questioned, as the rock is very fractured and groundwater in fractions may greatly alter the storage capacity of the rock.
DE: 5104 Fracture and flow
DE: 5114 Permeability and porosity
DE: 5120 Plasticity, diffusion, and creep
DE: 5139 Transport properties
DE: 0925 Magnetic and electrical methods
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting