No abstract

Portions of this document may be illegible in eledronic image products. Smages are produced from the best avaihble original dOCUIIlC!llL ABSTRACTExperimental and theoretical studies have been conducted to develop a quantitative understandig of the thennohydrologic phenomena induced by emplacement of high-level radioactive waste (HLW) in an unsaturated fractured porous media. A series of laboratory experiments was conducted in a variety of media to study the physics of thermally driven moisture redistribution. Principles of similarity theory were applied to develop dimensionless parameters to be used to predict thennohydrologic behavior at the field and repository scales from that observed at the laboratory scale. Numerical modeling of two-phase flow phenomena was used to evaluate the scaling theories and interpret the experimental results.Eleven laboratory-scale experiments were conducted which are categorized according to: (i) the fluid phase that is the focus of study, (ii) temperature regime, (iii) geometry, and (iv) test medium. These experiments centered on nonisothermal liquid flow and considered sub-boiling and boiling regimes in both unconsolidated and consolidated porous media A conceptual model was identified based on experimental results in which the thermal regime was characterized as having three distinct periods: (i) an initial heating period in which moisture is transported mostly as vapor, (ii) a transitional period when water moves as both liquid and vapor, and (iii) a cooling period during which water moves mostly as liquid only.Specific heat and mass transfer mechanisms and phenomena were identified using experimental results. Three different expressions of dryoutkondensation proximal to the heat source were observed in the experiments: (i) media with low permeability and a low air-entry value experienced a relatively narrow zone of moisture buildup immediately outside of the dryout zone, (ii) media with a relatively low permeability but with a large air-entry valuer experienced condensation over a broad area beyond the dryout zone. and (iii) media with a sufficiently high permeability did not experience a complete dryout zone nor an area of condensate buildup, even for heater temperatures as high as 170 "C. Resaturation rates measured in consolidated media during the cooling period were at least 10 times slower than drying rates measured during the heating period. Gas pressure buildup was observed in heated porous media, supporting the premise of the conceptual model that gas advection, and not buoyancy, will be the prominent water transport mechanism in media with sufficiently low permeability and with sufficiently high heat source tempemtures.The V-TOUGH computer code was used to simulate the heating, transitional, and cooling periods for three spatial scales: (i) laboratory (-cm); (ii) field (-m); and (iii) repository (-km). Calculations of the temperature, pressure, and saturation fields were used to evaluate the proposed scaling theories. The model simulations indicated that fluid...