Diffusive properties of granitic rock as measured by in-situ electrical methods
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Diffusion into the rock matrix has been identified as one of the most important retention mechanisms for dissolved contaminants in fractured crystalline rock. In this thesis the diffusive properties of granitic rock, described by the formation factor, have been investigated by electrical methods. These methods are based on the Einstein relation between diffusivity and ionic mobility. Formation factors have been obtained both in the laboratory and in deep lying rock in-situ.
At present, two locations in Sweden, Forsmark and Oskarshamn, are undergoing site investigations for the siting of a repository for spent nuclear fuel. As a part of these investigations, the formation factor of the rock surrounding five, 1000 m deep boreholes has been investigated. More than 250 rock samples, taken from the bore cores, have been investigated in the laboratory and around 50 000 formation factors have been obtained in-situ. The results have been treated statistically and it appears that the formation factor is lognormally distributed. The mean and standard deviation of the obtained log-normal distributions vary from site to site, depending on the geology. For intact granitic rock, the obtained formation factors range between 2.2·10-7 and 2.5·10-2.
The results suggest that diffusion into open, but hydraulically non-conductive fractures may have a significant influence on radionuclide retention by way of increasing it. Therefore, the fractured rock formation factor was introduced in addition to the traditional rock matrix formation factor. The retardation capacity of crystalline rock is strongly associated with the pore connectivity. In this thesis, it is shown that the micropore network of granitic rock is connected on, at least, a metre scale in-situ.
Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , x, 85 p.
Trita-KET, ISSN 1104-3466 ; 206
IdentifiersURN: urn:nbn:se:kth:diva-121ISBN: 91-7283-935-XOAI: oai:DiVA.org:kth-121DiVA: diva2:7002
2005-02-11, Sal D3, Lindstedtsvägen 5, Stockholm, 10:00
Vilks, Peter, Dr
QC 201010192005-02-092005-02-092010-10-19Bibliographically approved