Thermal-hydrological analysis of large-scale thermal tests in the exploratory studies facility at Yucca Mountain

In situ thermal tests, which are to be conducted in the Exploratory Studies Facility (ESF) at Yucca Mountain, will provide a major portion of the experimental basis supporting the validation of coupled thermal-hydrological-geomechanical-geochemicaI (T-H-M-C) process models required to assess the total system performance at the site. With respect to advective rock dryout, we have identified three major T-H flow regimes: (1) throttled, nonbuoyant, advective rock dryout; (2) unthrottled, nonbuoyant, advective rock dryout; and (3) unthrottled, buoyant, advective rock dryout. With the V-TOUGH code, we modeled a range of heater test sizes, heating rates, and heating durations under a range of plausible hydrological conditions to help optimize an in situ thermal test design that provides sufficient information for determining (a) the dominant mode(s) of heat flow, (b) the major T-H regime(s) and processes (such as vapor diffusion) that govern the magnitude and direction of vapor and condensate flow, and (c) the influence of heterogeneous properties and conditions on the flow of heat, vapor, and condensate. For the plate thermal test, which uniformly heats a disk-shaped area, we evaluated a wide range of test areas, ranging from 50 to 5077 m{sup 2}. We evaluated the single-drift thermal test, which consists of a row of large-waste-package-sized heaters sitting on the floor of the heater drift, and then developed an optimized thermal test configuration, called the single-drift, winged thermal test, in which the heater drift is flanked by wing heater arrays. For this configuration, we considered three heating schedules (with 1-, 2-, and 4-yr full-power heating periods) and three heating rates (122, 177, and 236 W/m{sup 2}). For determining the dominant T-H regime(s) and dominant heat-flow mode(s), the most important diagnostic measurements are vertical temperature and gas-phase pressure profiles and gas-phase pressure and relative humidity RH histories in the drift