No description available.

The groundwater travel time along the fastest path of likely radionuclide transport is a regulatory criterion used to assess the hydrogeologic quality of a high - level radioactive waste repository. Hydrologists and engineers are limited in their ability to define with confidence the fastest path, owing to the heterogeneous nature of geologic materials. Field measurements of hydraulic properties such as in test or observation wells, are inherently averages of properties at scales smaller than the scale of the field measurement. As a result of averaging, subscale information is lost and there is uncertainty in defining the fastest trajectory of groundwater. This scale problem is explained through a review of the continuum and REV concepts in groundwater hydrology. The application of hydrodynamic dispersion concepts is recommended as a means of incorporating the effect of subscale heterogeneity on the fastest groundwater travel time. Sources of uncertainties in predicting groundwater travel time are discussed in the report. The uncertainties are mainly attributed to the heterogeneous nature of geologic formations. The heterogeneity of geologic materials can, however, be characterized quantitatively using geostatistical methods. Important statistical parameters include mean and variance. as well as the spatial correlation structures of the hydrologic properties within the hydrogeologic system. These parameters may he obtained from limited data base. Stochastic methods, reviewed and explained in this report, can take advantage of the geostatistical characterization to predict large -scale groundwater flow and solute transport. Several examples from recent scientific literature are provided to illustrate the application of stochastic methods to the groundwater travel time analysis. Stochastic methods in subsurface hydrology have only recently been evaluated under field conditions for a few locations, and validation of the theories is incomplete, especially in unsaturated fractured rocks. Nevertheless, research efforts should continue to improve the state -of -the art. Geostatistics and stochastic methods will be valuable tools in addressing the groundwater travel time objective

The microwave induced plasma was used to sinter synthetic Idaho Chemical Processing Plant (ICPP) alumina and zirconia based high level nuclear waste calcines in a nitrogen atmosphere. The sintering behavior of these nuclear waste calcines was observed with identification of the phases formed. A sintered density of higher than 3.20 g/cm3 was obtained within 10 minutes of plasma sintering of pure calcines. The addition of frit in pure calcines to form glass-ceramics resulted in a decrease of density to less than 2.0 g/cm3. This was attributed to the reaction between frit and volatile substances in both zirconia based and alumina based calcines. The removal of volatile substances before sintering increased the sintered density of calcines. The lower sintered density was obtained for the more volatile samples. The phases formed in the plasma sintering of calcines were identified as a function of temperature and amount of frit.

No description available.

Thesis (M.S.)--University of Michigan, 1958. / Project completed 1957. Degree awarded Feb. 1958.

Thesis (M.S.)--University of Michigan, 1976.

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In the 1960's the Department of Energy at Oak Ridge National Laboratory designed eight 50,000 gallon storage tanks for the liquid nuclear waste. Each tank was designed with its own ventilation system to purge radiolytic hydrogen and oxygen from the tank. This design induced water removal and necessitated the additional requirement of entraining radioactivity from the exiting system by the use of demisters and HEPA filters. Up until the 1980's this was a sufficient method, via the hydrofracture process, of disposing the liquid nuclear waste. However since then, this method has been terminated and the tanks are nearing capacity. In the transfer of the liquid waste to the holding tanks, large amounts of water are used to prevent line clogging and solid build up in the pipes. Utilizing the existing system, this thesis proposes the idea of sparging air into the liquid waste and increasing the tank temperature in order to eliminate excess water. Parameters such as increasing the sparging air temperature, and dehumidifying and eliminating carbon dioxide from the sparging air, are investigated theoretically and experimentally in small scale experiments. In addition, the effects of vapor pressure lowering and its simultaneous effect on the evaporation rate are investigated through the activity coefficient of sodium nitrate, the major component of the liquid waste. Precipitate blockage formations in the sparging tube have also been addressed.

The application of multi-concentration group mathematical modelling to the leaching of radionuclide waste-forms which have continuous porous matrix such as cemented waste form is described. The modelling is illustrated analysing a hypothetical of some transport mechanisms such as molecular diffusion, ionic migration and convective flow for release of interest radionuclide from a solidified waste form which contains discrete particles of radioactive Sr-85 nuclides into the aqueous environment. The group parameters are derived from the classical electrochemistry concept of ion transport in dilute electrolytic solution. The numerical analysis is based on the Crank-Nicolson Implicit Methods which assures the stability of the solution at a practical time step. The results show that, for a short-time period of leaching in demineralized water the leaching behavior follows the predominating diffusion mechanism. After this point, the role of other processes apparent and continue until all radionuclides in the cement waste are leached out when compared to the Semi-Infinite Diffusion model which is based on pure diffusion mechanism. The multi-concentration group model can also be applied to long-term prediction of complicated release mechanisms of the radionuclides in the waste form of a particular disposal environment, unless the variables of interest such as the corrosion rate, the chemical reaction, erosion rate and etc. are determined by experiment or theoretical hypothesis. The appropriate differential equation then can be solved by the same general numerical approach. Also, the results of the modelling indicate which parameters should be measured experimentally in order to provide a quantitative test of the hypothetical release mechanism.