3 research outputs found
Recommended from our members
Colloid facilitated transport in fractured rocks : parameter estimation and comparison with experimental data.
Colloid-facilitated migration of plutonium in fractured rock has been implicated in both field and laboratory studies . Other reactive radionuclides may also experience enhanced mobility due to groundwater colloids. Model prediction of this process is necessary for assessment of contaminant boundaries in systems for which radionuclides are already in the groundwater and for performance assessment of potential repositories for radioactive waste. Therefore, a reactive transport model is developed and parameterized using results from controlled laboratory fracture column experiments. Silica, montmorillonite and clinoptilolite colloids are used in the experiments along with plutonium and Tritium . . The goal of the numerical model is to identify and parameterize the physical and chemical processes that affect the colloid-facilitated transport of plutonium in the fractures. The parameters used in this model are similar in form to those that might be used in a field-scale transport model
Recommended from our members
A refined approach to estimating effective flow porosity from cross-hole tracer tests in fractured media.
Simulations of flow and transport in two-dimensional representations of heterogeneous fractured media are used to investigate the errors and biases associated with effective flow porosity estimates derived from cross-hole tracer tests. A method is presented for constructing probability distributions of 'correction factors' that can be used to correct apparent flow porosities obtained from tracer tests to obtain 'true' flow porosities in fracture systems. Although only a limited number of the many possible variations in fracture flow system properties is investigated, it is concluded that effective flow porosities derived from cross-hole tracer tests have a strong tendency to overpredict true flow porosities in fracture flow systems. This tendency toward overprediction decreases as the fracture conductivity relative to the background conductivity field decreases and as the orientation of the most conductive fractures becomes better aligned with the two wells. Tracer tests with small amounts of recirculation of water from the production well to the injection well are predicted to result in much better estimates of true flow porosity (on average), and with much less variability in the estimates, than tests with no reclrculation. However, the advantage offered by recirculation decreases as the fracture conductivity relative to the background conductivity decreases
Recommended from our members
Estimates of ambient groundwater velocity in the alluvium south of Yucca Mountain from single-well tracer tests.
The saturated alluvium located south of Yucca Mountain, Nevada is expected to serve as the final barrier to radionuclide transport from the proposed high-level nuclear waste repository at Yucca Mountain. The alluvium will act as a barrier if radionuclides breach the engineered barriers in the repository, move through the unsaturated zone beneath the repository to the water table, and then migrate through saturated volcanic tuffs to the alluvium. Three single-well injection-withdrawal tracer tests were conducted between December 2000 and April 2001 in the saturated alluviuni at NC-EWDP-19D1, a Nye County-Early Warning Drilling Program well located about 18 km south of Yucca Mountain. The tests had the objectives of (1) distinguishing between a single- and a dual-porosity conceptual radionuclide transport model for the alluvium, and (2) obtaining estimates of ambient groundwater velocity in the alluvium