Experimental and numerical investigation of flow phenomena in nonisothermal variably saturated bentonite-crushed rock mixtures
article
Mixtures of sodium bentonite and crushed rock are being examined as components of the engineered barrier system in a geologic repository of high-level nuclear waste. Laboratory experiments were performed to determine the thermal and unsaturated hydraulic properties of bentonite-crushed diorite mixtures. Water-retention curves were obtained from conventional pressure cell and evaporation experiments. In addition, transient data from heating and gas injection experiments on laboratory columns were analyzed using inverse modeling techniques. Measured pressures, temperatures, and drained-water volumes were jointly inverted to estimate absolute permeability, thermal conductivity, specific heat, and capillary strength parameters. Simultaneous matching of all available data-specifically the gas breakthrough at the top of the column-proved difficult, pointing toward aspects of the experimental design and the conceptual model that need to be refined. The analysis of sensitivity coefficients and the correlation structure of the parameters revealed the importance of accurately capturing coupled thermal hydrological processes within the column as well as the details of the experimental apparatus, such as heat losses and storage of water and gas in the measuring burette. The parameters estimated using different experimental and analytical procedures were consistent with one another, providing backfill material properties useful for the simulation of gas- and heat-generating nuclear waste repositories.
Topics
BentoniteDigital storageGeological repositoriesInverse problemsMixturesRadioactive wastesSensitivity analysisSpecific heatEngineered barrier sys-temExperimental apparatusHigh level nuclear wastesLaboratory experimentsNuclear waste repositoriesNumerical investigationsSensitivity coefficientUnsaturated hydraulic propertiesThermal conductivity
TNO Identifier
953701
ISSN
15391663
Source
Vadose Zone Journal, 2(2), pp. 239-246.
Pages
239-246
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