Thermal Properties of Clay-Based Buffer Materials for a Nuclear Fuel Waste Disposal Vault

摘要

The thermal properties of three types of bentonite clay, one illite-rich shale and one kaolin mixed with crushed granite were investigated. Thermal conductivity measurements were made over a range of mix proportions, moisture content, density and ambient temperature using the transient heat-probe method. The effects of thermal drying in the buffer zone prior to water uptake were investigted by means of laboratory-scale heater experiments. Illite-rich shale (Sealbond) and kaolin exhibited better compactability and thermal conductivity than the bentonite clays. The thermal conductivity of all types of clay buffers showed a high degree of moisture dependency and relatively no effect due to elevated temperature under high fluid pressure conditions. Bentonite buffers compacted to a dry density of 1200 to 1400 kg/m sup 3 showed extensive cracking due to differential shrinkage. Addition of crushed granite, and/or compaction to a higher density, reduced the thermal cracking of the buffer material. 11 refs., 31 figs., 9 tabs. (ERA citation 11:030147)