A Conversion of the Measured Anisotropic Thermal Properties by Transient Plane Heat Source to the Isotropic Thermal Properties

摘要

The Swedish Nuclear Fuel and Waste Management Company has undertaken site characterization with the objective of locate a geological repository for spent nuclear fuel. This includes determination of the thermal properties of the rock at potential sites in different scales and the in-situ temperature, both of which are design parameters for canister spacing. Consequently, the thermal characteristics of the site influence the size and capacity of the repository. Anisotropic thermal properties of six specimens from drill hole KFM90B, Forsmark, Sweden, have been measured previously in the laboratory (small scale). The determination of the thermal properties was based on a direct measurement method, the so called "Transient Plane Source" (TPS) Method. In this paper, the measured anisotropic thermal properties are theoretically analysed by assuming that the specimens are isotropic. While this assumption is not correct for these specimens, the results of such an analysis give valuable information concerning other measurements that have been performed using the isotropic assumption. The results of the analysis show that choosing the isotropic assumption for anisotropic specimens leads to conspicuous differences in small scale measurements. The differences become more critical when there is a strong anisotropy between different directions in the specimen.