Study on effective thermal conductivity of the local buffer material in Taiwan

Abstract

The characterization of thermal conductivity of the buffer/backfill material is of great importance for dissipating the decay heat of the spent nuclear fuel and safety estimates of disposal site. The buffer/backfill material is usually a kind of complex material, which includes multi composition particles and multi-phase systems in which nearly all the constituents are distributed randomly. Its properties are complicated and that is dependent on all the constituents of material. Therefore, this study’s purpose is to assess the effective thermal conductivity of the Zhihsin clay from Taiwan. First, the matrix material property of Zhihsin clay was obtained by heat transfer, statistics and probability methodology in considering constituents and distribution types. Relative to other bentonites, the effective properties of Zhihsin clay have a higher uncertainty due to the fewer smectite and more complicated compositions. Then, this study takes the matrix material result to estimate the effective values. The ETC of solid of the Zhihsin clay was obtained as normal distribution form N(2.33, 0.07). The results show that the effective values have nonlinear changes under various porosities and saturations. Finally, the equation of the effective thermal conductivity was received by the design of experiment and response surface methodology. In the regression analysis, porosity multiply saturation is one of significant model terms. It represents that the effective thermal conductivity was affected by interaction between porosity and saturation.