Hygrothermal performance of an engineered clay barrier during sustained heating

Bentonitic clay buffers, with a potential for swelling, form an integral part of the natural (geological formation)/engineered multi-barrier concepts being proposed for the disposal of heat-generating radioactive nuclear fuel wastes. The integrity of such barriers during thermal loadings is of primary interest to the assessment of their reliability. This paper discusses the results of a series of experiments performed to assess the performance of buffer material under sustained heating. These experiments were conducted in a large-scale granite block facility. The laboratory modeling approximately simulates the local environment that can be encountered in a disposal vault in a granitic rock mass. Experiments in which the power supply to an embedded heater was held constant are described. The temperature distributions within the buffer and the granite block together with the residual moisture content distributions are documented. Also discussed is the application of a computational model of coupled heat and moisture flows. Moisture and heat transfer in the buffer under coupled gradients is described by the Philip-de Vries-type model in which the hygrothermal parameters are determined separately