https://digital.library.unt.edu/ark:/67531/metadc898741/m2/1/high_res_d/928560.pdf

Performance of a buried radioactive high level waste (HLW) glass after 24 years

Static leach tests have been performed at glass surface area/leachant volume (SA/V) ratios of 10, 340, 2,000, and 20,000 m[sup [minus]1] to assess the effects of the SA/V on the mechanism and rate of the glass reaction. Tests were performed using actinide-doped borosilicate waste glasses [Savannah River Laboratory (SRL) 131 and SRL 202] to monitor the distribution of released radionuclides in tests at different SA/V. Solution results show the major effect of the SA/V to be dilution of reaction of products. Differences in the pH and silicic acid concentrations attained in tests at different SA/V then affect the reaction rate. Tests at low SA/V maintain leachate pH values similar to the initial leachant, while tests at higher SA/V result in higher leachate pH values being attained due to ion-exchange reactions. Transuranics released as the glass corrodes may exist in the leachate in concentrations far above their solubility limits by sorbing onto colloids, although the colloids may eventually settle out of solution. Transuranics also sorb onto the steel reaction vessel. The glass reaction progress can be characterized by three stages: (a) an initial stage where the reaction rate depends on the leachant pH, (b) an intermediate stage where the reaction slowsmore » toward a minimum rate as the leachate solution approaches saturation,'' and (c) a long-term stage where the reaction rate may be affected by the formation of secondary phases that control the solution chemistry. Tests at different SA/V cannot always be compared directly because the dominant reaction step and the observed reaction stage (initial, intermediate, or long-term) may not be the same.« less

A comparison of glass reaction at high and low glass surface/solution volume

The main immobilization technologies that have been demonstrated for radioactive waste disposal are cementation, bituminization, and vitrification. Vitrification is currently the most widely used technology for the treatment of high level radioactive wastes (HLW) throughout the world. Nations that have generated HLW are immobilizing in either alkali borosilicate glass or alkali aluminophosphate glass. The compositions of nuclear waste glasses are tailored for easy preparation and melting, avoidance of glass-in-glass phase separation, avoidance of uncontrolled crystallization, and acceptable chemical durability. Future waste generation is driven by interest in sources of clean energy. The development of advanced waste forms is a necessary component of the new nuclear power plant (NPP) flowsheets. A brief summary is given of existing and advanced waste forms and processing technologies.

Radioactive waste (RAW) conditioning, immobilization, and encapsulation processes and technologies: overview and advances

Vitrification of borate waste from nuclear power plant using coal fly ash. (II) Leaching behavior of the FA30 glass

The meteoric alteration of basaltic glass in hyaloclastite (0.55 to 0.2 Ma) from Jeju Island, Korea, was examined using high-resolution electron microscopy, in situ sample preparation using focused ion beam, and microchemical analysis. The glass particles showed a sequential development of alteration textures toward the glass interior as follows: oscillatory zoning of smectite and amorphous bands/hemispheres, congruent dissolution of glass with smectite infilling in interparticle pore, and the replacement of nanogranular amorphous aggregate (NAA) for porous leached glass (LG) followed by a partial crystallization of smectite. Chemical compositions of LG widely varied from partial to complete leaching of almost all kinds of cations, to a preferred leaching of Na only. The order of leaching in LG followed Na + >Mg 2+ >Ca 2+ = Fe 2+ >Al 3+ >Ti 4+ . Leached cations were removed from the hyaloclastite-water system or incorporated into secondary phases. Sodium was all but removed from the system. Magnesium was largely lost with partial incorporation into smectite. Calcium was significantly retained in NAA, partly incorporated into the smectite interlayer, and partly lost. Iron and Al were partitioned between NAA and smectite. Titanium was mostly retained in NAA and Ti-rich silicates. The molar ratio of major cations to Si was reversed from Ca 2+ >Mg 2+ >Na + in basaltic glass to Na + >Mg 2+ >Ca 2+ in groundwater. The geochemical evolution of pore water was influenced by the microtextural and microchemical evolution of glass particles, and vice versa. Systematic microtextural, microchemical, and mineralogical analyses of natural glass alteration are critical to understanding the long-term behavior of glass alteration.

Microtextures, microchemistry, and mineralogy of basaltic glass alteration, Jeju Island, Korea, with implications for elemental behavior

This report provides an overview of progress during FY 1991 for the Technical Support Program that is part of the ANL Technology Support Activity for DOE, Environmental Restoration and Waste Management (EM). The purpose is to evaluate, before hot start-up of the Defenses Waste Processing Facility (DWPF) and the West Valley Demonstration Project (WVDP), factors that are likely to affect glass reaction in an unsaturated environment typical of what may be expected for the candidate Yucca Mountain repository site. Specific goals for the testing program include the following: (1) to review and evaluate available information on parameters that will be important in establishing the long-term performance of glass in a repository environment; (2) to perform testing to further quantify the effects of important variables where there are deficiencies in the available data; and (3) to initiate long-term testing that will bound glass performance under a range of conditions applicable to repository disposal.

/pdf/anl-technical-support-program-for-doe-environmental-2pf9shh5ot.pdf

ANL Technical Support Program for DOE Environmental Restoration and Waste Management. Annual report, October 1990--September 1991

Basalt glass has been used as a natural analogue of high-level waste glass because both types of glass have similar Si contents. Most important for identifying the dominant long-term corrosion process is the exact chemical nature of the glass-palagonite boundary. In this paper, the authors present the results of a detailed study of alteration interfaces formed in subaerially altered Hawaiian basalt glasses (400 to 700 years old) and analyzed with high resolution transmission electron microscopy (TEM) and nanometer-size energy dispersive x-ray spectrometric (EDS) probe. The study reveals a sharp contact between fresh glass and alteration products at nanometer scale. The alteration products, which were typically several nanometers in size, were found to be iron oxide hydroxide (goethite), aluminum hydroxide hydrate (scarbroite), and an Si-Fe-Al rich amorphous phase. The EDS line profile across the boundary showed a zone of 60--130 nm thickness that is depleted in alkali elements but exhibits no variation for silicon. These results point to a dominant dissolution-precipitation mechanism plus a limited ion-exchange process under subaerial conditions.

An AEM study of glass-palagonite interfaces formed in Hawaiian basalt glasses

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ANL Technical Support Program for DOE Environmental Restoration and Waste Management. Annual report, October 1990--September 1991

An AEM study of glass-palagonite interfaces formed in Hawaiian basalt glasses