This study investigates the use of ‘simple’ glasses, comprising six components, to represent the structure of complex LAW glasses proposed for Immobilized Low Activity Wastes from the Hanford site in the USA. The 18 elements present in ILAW glasses LAW A44, ORP LB2, and LAW A23 were represented by Al2O3, B2O3, CaO, Na2O, SiO2, and ZrO2 according to their coordination chemistry and their roles as network formers and modifiers. The dissolution behavior of each ‘simple’ glass was compared to its corresponding candidate “complex” LAW glass through PCT-B tests. Significant differences were observed; the durability of complex glasses was concluded to be LAW A44 > ORP LB2 ≥ LAW A23 whereas in their simplified versions the order was LAW A44 > LAW A23 > ORP LB2. These results are discussed in relation to compositional differences and highlight the importance of minor glass components in controlling glass durability. The implications of these results for the use of simplified glass compositions are discussed.

Types of melter feed materials affect glass production rates. This study focuses on the effects of alumina sources on melting behavior of high-alumina high-level-waste melter feeds containing different alumina sources, namely, gibbsite, boehmite, and corundum. The heat flow from the glass melt to the cold cap, a floating layer of the reacting feed, is partially hindered by a foam layer at the bottom of the cold cap. Volume expansion tests and thermoanalytical methods revealed that a slow-melting feed with corundum foamed extensively, whereas a fast-melting feed with boehmite had a low reaction heat and produced less stable foam. The foam thickness, a critical factor for the rate of melting, estimated using the relationship between the heat conductivity and foam porosity was in reasonable agreement with experimental observation.

This work is based upon the notion that a grid of electrodes will be incorporated in the slurry of radioactive waste and grout-forming solids. These electrodes will remain in the hardened grout, and will serve to monitor the ionic concentration of the liquids contained within the matrix, the structural integrity of the matrix, and the rates of out-diffusion of the electrolytes. Ultimately, we will investigate four techniques: (1) ionic conductivity, (2) electrochemical potential, (3) cyclic voltammetry, and (4) impedance measurements. Eventually, the results will be correlated with present quality verification methods, which include recovering samples and following the Toxicity Characteristic Leach Procedure (or other such accepted standard tests). This paper presents the preliminary results of a recently initiated effort.

The widely held explanation for mechanical failure of silicate and silica glasses rests upon the existence of Griffith-flaw and associated free ion diffusion concepts used to model crack growth. However, this theory has consistently failed to provide complete agreement with the experimental results. This dilemma coupled with the reports of single-valued strengths in fibers cannot be rationalized by the modification of the intrinsic Griffith-flaw distribution to essentially a delta function.

It is for these reasons that the field-enhanced ion diffusion model has been introduced. The inclusion of a term for the electrostatic potential in the thin-film solution of Fick's second law has been shown to be consistent with the experimental results. Therefore, the effects on alkali ion migration as a consequence of the local variations in charge density that occur on the solution side of the glass/water interface play a direct role on the chemical corrosion mechanism. Thus chemistry which can modify the surface potential can alter the rate of aging of glass.

It has been found that the chemistry which has been used to modify the corrosion behavior of glass fibers can also alter composite properties. These modifications no doubt arise from changes in the interphase region.

We report on the effects of treatments on initial fiber strengths, aging resistance, and preliminary results of composite properties (made from our treated fibers).