Publications

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This new program at Sandia is focused on Iodine waste form development for GNEP cycle needs. Our research has a general theme of 'Waste Forms by Design' in which we are focused on silver loaded zeolite waste forms and related metal loaded zeolites that can be validated for chosen GNEP cycle designs. With that theme, we are interested in materials flexibility for iodine feed stream and sequestration material (in a sense, the ability to develop a universal material independent on the waste stream composition). We also are designing the flexibility to work in a variety of repository or storage scenarios. This is possible by studying the structure/property relationship of existing waste forms and optimizing them to our current needs. Furthermore, by understanding the properties of the waste and the storage forms we may be able to predict their long-term behavior and stability. Finally, we are working collaboratively with the Waste Form Development Campaign to ensure materials durability and stability testing.

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With the lowering of the EPA maximum contaminant level of arsenic from 50 parts per billion (ppb) to 10 ppb, many public water systems in the country and in New Mexico in particular, are faced with making decisions about how to bring their system into compliance. This document provides detail on the options available to the water systems and the steps they need to take to achieve compliance with this regulation. Additionally, this document provides extensive resources and reference information for additional outreach support, financing options, vendors for treatment systems, and media pilot project results.

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This document defines a standardized screening protocol for use in developing iodine ''getters'' for placement in the proposed YMP-repository invert. The work was funded by the US Department of Energy (DOE), Office of Civilian Radioactive Waste Management (OCRWM), Office of Science and Technology International (S&T) during 2004-2005. First, the likely environmental conditions in the invert are reviewed as a basis for defining the thermal and geochemical regimes in which a getter must function. These considerations, then, served as the basis for laying out a hierarchy of materials screening tests (Table 1). An experimental design for carrying out these screening tests follows next. Finally, the latter half of the document develops methods for preparing test solutions with chemistries that relate to various aspects of the YMP-repository environment (or, at least to such representations as were available from program documents late in 2004). Throughout the document priority was given to defining procedures that would quickly screen out unpromising candidate materials with a minimum amount of labor. Hence, the proposed protocol relies on batch tests over relatively short times, and on a hierarchy of short pre-test conditioning steps. So as not to repeat the mistakes (and frustrations) encountered in the past (notably in preparing WIPP test brines) particular care was also given to developing standardized test solution recipes that could be prepared easily and reproducibly. This document is principally intended for use as a decision-making tool in evaluating and planning research activities. It is explicitly NOT a roadmap for qualifying getters for actual placement in the repository. That would require a comprehensive test plan and a substantial consensus building effort. This document is also not intended to provide a complete list of all the tests that individuals may wish to carry out. Various materials will have their own peculiar concerns that will call for additional specialized tests. In many cases additional research will also be needed to verify the exact nature of the chemical process responsible for scavenging the iodine from the test solutions.

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This report documents a field trial program carried out at Well No.15 located at Kirtland Air Force Base, Albuquerque, New Mexico, to evaluate the performance of two relatively new arsenic removal media, ALCAN-AASF50 (ferric coated activated alumina) and granular ferric hydroxide (US Filter-GFH). The field trial program showed that both media were able to remove arsenate and meet the new total arsenic maximum contaminant level (MCL) in drinking water of 10 {micro}g/L. The arsenate removal capacity was defined at a breakthrough effluent concentration of 5 {micro}g/L arsenic (50% of the arsenic MCL of 10 {micro}g/L). At an influent pH of 8.1 {+-} 0.4, the arsenate removal capacity of AASF50 was 33.5 mg As(V)/L of dry media (29.9 {micro}g As(V)/g of media on a dry basis). At an influent pH of 7.2 {+-} 0.3, the arsenate removal capacity of GFH was 155 mg As(V)/L of wet media (286 {micro}g As(V)/g of media on a dry basis). Silicate, fluoride, and bicarbonate ions are removed by ALCAN AASF50. Chloride, nitrate, and sulfate ions were not removed by AASF50. The GFH media also removed silicate and bicarbonate ions; however, it did not remove fluoride, chloride, nitrate, and sulfate ions. Differences in the media performance partly reflect the variations in the feed-water pH between the 2 tests. Both the exhausted AASF50 and GFH media passed the Toxicity Characteristic Leaching Procedure (TCLP) test with respect to arsenic and therefore could be disposed as nonhazardous waste.

Techniques for mitigating the adsorption of {sup 137}Cs and {sup 60}Co on metal surfaces (e.g. RAM packages) exposed to contaminated water (e.g. spent-fuel pools) have been developed and experimentally verified. The techniques are also effective in removing some of the {sup 60}Co and {sup 137}Cs that may have been adsorbed on the surfaces after removal from the contaminated water. The principle for the {sup 137}Cs mitigation technique is based upon ion-exchange processes. In contrast, {sup 60}Co contamination primarily resides in minute particles of crud that become lodged on cask surfaces. Crud is an insoluble Fe-Ni-Cr oxide that forms colloidal-sized particles as reactor cooling systems corrode. Because of the similarity between Ni{sup 2+} and Co{sup 2+}, crud is able to scavenge and retain traces of cobalt as it forms. A number of organic compounds have a great specificity for combining with nickel and cobalt. Ongoing research is investigating the effectiveness of chemical complexing agent EDTA with regard to its ability to dissolve the host phase (crud) thereby liberating the entrained {sup 60}Co into a solution where it can be rinsed away.

An environmentally friendly method and materials study for desalinating inland brackish waters (i.e., coal bed methane produced waters) using a set of ion-exchange materials is presented. This desalination process effectively removes anions and cations in separate steps with minimal caustic waste generation. The anion-exchange material, hydrotalcite (HTC), exhibits an ion-exchange capacity (IEC) of {approx} 3 mequiv g{sup -1}. The cation-exchange material, an amorphous aluminosilicate permutite-like material, (Na{sub x+2y}Al{sub x}Si{sub 1-x}O{sub 2+y}), has an IEC of {approx}2.5 mequiv g{sup -1}. These ion-exchange materials were studied and optimized because of their specific ion-exchange capacity for the ions of interest and their ability to function in the temperature and pH regions necessary for cost and energy effectiveness. Room temperature, minimum pressure column studies (once-pass through) on simulant brackish water (total dissolved solids (TDS) = 2222 ppm) resulted in water containing TDS = 25 ppm. A second once-pass through column study on actual produced water (TDS = {approx}11,000) with a high carbonate concentration used an additional lime softening step and resulted in a decreased TDS of 600 ppm.

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Techniques for mitigating the adsorption of {sup 137}Cs and {sup 60}Co on metal surfaces (e.g. RAM packages) exposed to contaminated water (e.g. spent-fuel pools) have been developed and experimentally verified. The techniques are also effective in removing some of the {sup 60}Co and {sup 137}Cs that may have been adsorbed on the surfaces after removal from the contaminated water. The principle for the {sup 137}Cs mitigation technique is based upon ion-exchange processes. In contrast, {sup 60}Co contamination primarily resides in minute particles of crud that become lodged on cask surfaces. Crud is an insoluble Fe-Ni-Cr oxide that forms colloidal-sized particles as reactor cooling systems corrode. Because of the similarity between Ni{sup 2+} and Co{sup 2+}, crud is able to scavenge and retain traces of cobalt as it forms. A number of organic compounds have a great specificity for combining with nickel and cobalt. Ongoing research is investigating the effectiveness of chemical complexing agent EDTA with regard to its ability to dissolve the host phase (crud) thereby liberating the entrained {sup 60}Co into a solution where it can be rinsed away.

The need for fresh water has increased exponentially during the last several decades due to the continuous growth of human population and industrial and agricultural activities. Yet existing resources are limited often because of their high salinity. This unfavorable situation requires the development of new, long-term strategies and alternative technologies for desalination of saline waters presently not being used to supply the population growth occurring in arid regions. We have developed a novel environmentally friendly method for desalinating inland brackish waters. This process can be applied to either brackish ground water or produced waters (i.e., coal-bed methane or oil and gas produced waters). Using a set of ion exchange and sorption materials, our process effectively removes anions and cations in separate steps. The ion exchange materials were chosen because of their specific selectivity for ions of interest, and for their ability to work in the temperature and pH regions necessary for cost and energy effectiveness. For anion exchange, we have focused on hydrotalcite (HTC), a layered hydroxide similar to clay in structure. For cation exchange, we have developed an amorphous silica material that has enhanced cation (in particular Na{sup +}) selectivity. In the case of produced waters with high concentrations of Ca{sup 2+}, a lime softening step is included.

The long-range objective of this study was to develop chemically assisted technologies for removing heels from tanks. In FY 01, the first two steps toward this objective were taken: (1) catalogue the occurrence and nature of tank heels and assess which materials are available for study and (2) develop methods for synthesizing non-radioactive surrogate heel materials for use in testing potential removal technologies. The chief finding of Task 1 was the existence of ''heels'', depending on the definition used. Hard materials that would be almost impossible to remove by sluicing are all but absent from the records of both Savannah River and Hanford. Historical usage suggests that the term ''heel'' may also apply to chunky, granular, or semi-solid pasty accumulations. These materials are documented and may also be difficult to remove by conventional sluicing technologies. Such heels may be comprised of normal sludge components, dominantly iron and aluminum hydroxides, or they may result from added materials which were not part of the normal fuel reprocessing operations: Portland cement, diatomaceous earth, sand and soil and spent zeolite ion exchange ''resins''. The occurrence and chemistry of the most notable ''heel'', that of the zeolite mass in Tank 19F at Savannah River, is reviewed in some detail. Secondly, no clear correlation was found between high tank temperatures and difficulties encountered in removing materials from a tank at a later date; nor did the sludges from these tanks give any indication of being particularly solid. Experimental studies to develop synthetic heel materials were caned out using a number of different approaches. For normal sludge materials settling, even when assisted by a centrifuge, it proved ineffective. The same result was obtained from drying sludge samples. Even exposing sludges to a molten salt melt at 233 C, only produced a fine powder, rather than a resilient ceramic which resisted disaggregation. A cohesive material, however, was produced by wicking the pore fluid out of a sludge gel (into packed diatomaceous earth), while simultaneously applying pressure to compact the sludge as it dehydrated. Osmotic gradients could provide the same function as the capillary forces provided by the diatomaceous earth sorbant placed in contact with the sludge. Tests on the anomalous materials added to the tanks all indicated potential problems. Hard granules, and maybe chunks, may be encountered where Portland cement was added to a tank. Sand, spent zeolite resin, and diatomaceous earth, will all react with the tank fluids to produce a sodalite/cancrinite material. The degree of reaction determines whether the grains become cemented together. SRS activities showed that heels formed when spent zeolites were added to tanks can be readily dislodged and it is expected that heels from sand would possess equal or less cohesion. Diatomaceous earth may form more resilient crusts or masses. To summarize, the existence of ''hard'' heels has yet to be documented. A broader definition suggests inclusion of poorly cohesive cancrinite-cemented masses and dense past-like accumulations of abnormally compacted ''normal'' sludges. Chemical treatments to remove these materials must focus on agents that are active against aluminosilicates and hydrous oxides of iron and aluminum. Exploiting the high pore-water content of these materials may provide a second avenue for dislodging such accumulations. Techniques were developed to produce synthetic sludges on which various removal technologies could be tried.

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Contaminant release scenarios proposed for the Waste Isolation Pilot Plant (WIPP) repository suggest that the Culebra Dolomite member of the Rustler Formation could be an important radionuclide release path. This thin, vuggy, highly fractured unit is the most transmissive geologic unit overlying the WIPP. Many of the samples obtained from drill cores in the Culebra exhibit fractures that are lined with iron-oxyhydroxide-rich and clay-rich mineral coatings. The coatings are mineralogically distinct from the rock matrix, and may have sorptive characteristics that are different from a clay-poor dolomite matrix. Where locally abundant, such coatings could affect advective/diffusive exchange between matrix blocks and fractures and the accessible mineral surface area available for radionuclide adsorption. Clay minerals are present in the matrix and as fracture coatings in the samples from all the drill core locations examined in this study. Visual examination of rock sample surfaces in the H -19b7 core suggests that at least 7% of the total fracture surface area is coated with iron oxhydroxides or clays. In the samples from H-19b7, the amount of clay disseminated in the matrix varies from <1% to {approx}12 % by weight, and generally increases with stratigraphic height within the unit. In a suite of samples obtained from 12 other locations in the vicinity of the WIPP site, matrix samples from the Culebra contain 0.6--7% clay. These samples were taken from the more transmissive lower two-thirds of the unit (Culebra Units 2-4) which was considered to be the accessible portion of the unit in the WIPP Compliance Certification Application (CCA). Clay minerals also occur as clay-rich laminae and partings with the geometries of primary sedimentary structures and dissolution residues. Such partings are the loci of bedding plane fractures, and have the heaviest clay coatings found in the unit. Crosscutting fractures also commonly exhibit clay mineral coatings, but these are generally discontinuous and much thinner.

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