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A mechanistic computer model is presented which predicts the 3-D cavity growth during the gasification phase of underground coal gasification. Developed for swelling bituminous coals, the model also obtains reasonable cavity width and length values for shrinking sub-bituminous coals. The model predicts cavity shape and burn-through times based on the coal properties, seam thickness, water reacting and the interwell distance. Employing a 2-D boundary layer model to determine the convective diffusion rate of oxygen to the reacting walls, it is found that natural convection diffusion must be included. The model includes flow in the injection region, the swirling, mixing effect in the cavity, and transitions from thick to thin seam geometry. Simulations of the Hanna II, Phase 2 and Pricetown I field tests, as well as a parametric study on Pittsburgh seam coal, are presented.

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A preliminary two-dimensionalmodel for In-situ underground coal gasification is presented for cifscussion. The model describes cavity formation from the injection well end and link zone burn up, where the initial link zone geometry is assumed at this time. Cavity growth is predicted via an integral boundary layer analysis with boundary conditions determined by oxygen mass transfer to the wall for forced and natural convection. Preliminary results are based on carbon oxiciation, the reduction of C029 and the water-gas reaction, but exclude reaction rate effectrs. The effect of water inilux is discussed. A comparison between EasterI (Pricetown)and Western (Hanna) coals is presented, as well as dimensionlessplots which indicate sin+arity solutions for various blast flow ratea.

A final vitrified waste form composition, based upon the chemical compositions of the input waste streams, is recommended for the transuranic-contaminated waste stored at the Transuranic Storage Area of the Radioactive Waste Management Complex at the Idaho National Engineering Laboratory. The quantities of waste are large with a considerable uncertainty in the distribution of various waste materials. It is therefore impractical to mix the input waste streams into an "average" transuranic-contaminated waste. As a result, waste stream input to a melter could vary widely in composition, with the potential of affecting the composition and properties of' the final waste form. This work examines the extent of the variation in the input waste streams, as well as the final waste form under conditions of adding different amounts of soil. Five prominent Rocky Flats Plant 740 waste streams are considered, as well as nonspecial metals and the "average" transuranic-contaminated waste streams. The metals waste stream is the most extreme variation and results indicate that if an average of approximately 60 wt% of the mixture is soil, the final waste form will be predominantly silica, alumina, alkaline earth oxides, and iron oxide. This composition will have consistent properties in the final waste form, including high leach resistance, irrespective of the variation in waste stream. For other waste streams, much less or no soil could be required to yield a leach resistant waste form but with varying properties.

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