Ruthenium-106 has been observed to migrate in ground water at about the same velocity as tritium from the site of an underground nuclear explosion to a pumped satellite well 91 meters distant. This finding contradicts the prediction, based on laboratory batch sorption measurements, that ruthenium-106 should migrate at a much lower rate than tritium. To predict migration of radionuclides in ground water, more relevant laboratory measurements are required.
For a nuclear waste repository in the unsaturated zone at Yucca Mountain, there are two thermal loading approaches to using decay heat constructively-that is, to substantially reduce relative humidity and liquid flow near waste packages for a considerable time, and thereby limit waste package degradation and radionuclide dissolution and release. “Extended dryout” achieves these effects with a thermal load high enough to generate large-scale (coalesced) rock dryout. “Localized dryout”(which uses wide drift spacing and a thermal load too low for coalesced dryout) achieves them by maintaining a large temperature difference between the waste package and drift wail; this is done with close waste package spacing (generating a high line-heat load) and/or low-thermal-conductivity backfill in the drift. Backfill can greatly reduce relative humidity on the waste package in both the localized and extended dryout approaches. Besides using decay heat constructively, localized dryout reduces the possibility that far-field temperature rise and condensate buildup above the drifts might adversely affect waste isolation.
Data have gradually been accumu lated on the physical properties of nuclear test sites at the U.S. Energy Research and Development Administration (USERDA) Navada Test Site (NTS) since underground testing began there in 1957. These data have been stored in the Lawrence Livermore Laboratory (LLL) K-Division Test Effects Data P=mk. This report briefly describes the principal test areas (Yucca Flat, Fahute Mesa, and Rainier Mesa) and media (alluvium, tuff, Climax Stock (granite) and Paleozoic rocks) at NTS. Background information is given on the data base and the various Nuclear explosives have been tested underground at the USERDA (formerly USAEC) NTS since 1957. Since 1963, when the Limited Test Ban Treaty went into effect, all U.S. testing has been underground. During this time, data have gradually been collected on the physical properties of the test media at NTS test areas. Much of the data has been collected methods used to measure geophysical parameters at NTS are described. The mean, standard deviation, and range of values for each test area and medium are given. However, specific properties for individual sites are not contained in this report. Properties for which averages are given include overburden and working-point density; seismic velocity both near the working point and from the working point to the surface; and water content, porosity, and water saturation of the rocks in the working point vicinity. to evaluate specific locations for proposed nuclear tests with respect to containment of radioactivity. However, some of the data is also of interest to workers in the seismic-coupling field. In particular, there is much interest in the low-coupling "dry" alluvium in the Yucca Flat test area.
Tlweedimensional calculations that explicitly represent a realistic mixture of waste packages (W%) are used to analyze decay-heat-driven thermal-hydrological behavior around emplacement drifts in a potential high-level waste facility at Yucca Mountain. Calculations, using the Nt.JIT code, compare two fundamentally different ways that WPs can be arranged in the repository, with a focus on temperature, relative humidity, and liquid-phase flux on WPs. These quantities strongly affect WP integrity and the mobilization and release of radionuclides from WPS. Point-load spacing, which places the WPs roughl y equidistant from each other, thermally isolates WPS from each other, causing large variability in temperature, relative humidity, and liquid-phase flux along the drifts. Line-load spaang, which places WPS nearly end to end in widely spaced drifts, results in more locally intensive and uniform heating along the drifts, causing hotter, drier, and more uniform conditions. A larger and more persistent reduction in relative humidity on WPS occurs if the drifts are backfilled with a low-thermal-conductivity granular material with hydrologic properties that minimize moisture wicking.
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