89 research outputs found
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Elemental Composition of a Composite of Samples HTF-E-03-162 to 164 From Tank 51H to Evaluate Acceptability of the Sludge for Transfer to Tank 40H and Processing in the DWPF
Three dip samples of suspended sludge slurry were obtained from Tank 51H and sent to the Savannah River Technology Center for analysis. The composite of these samples is intended as a confirmatory sample to evaluate the acceptability of the Tank 51H sludge slurry for transfer to Tank 40H and for eventual processing in the Defense Waste Processing Facility. This report presents results of analyses requested by the Defense Waste Processing Facility for this evaluation. These analyses included the measurement of the concentrations of twenty two elements in the sludge slurry and the determination of the weight percent calcined solids of the slurry
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Leaching Tc-99 from SRP glass in simulated tuff and salt groundwaters
Results of leach tests with Tc-99 doped SRP borosilicate waste glass are presented. The glass was prepared by melting a mixture of SRP 165 powdered frit doped with a carrier free solution of Tc-99 at 1150{sup 0}C. Dissolution of portions of the resulting glass indicated that the Tc-99 was distributed homogeneously throughout the glass. Static leach tests up to 90 days were performed at 90{sup 0}C in J-13 tuff groundwater or WIPP brine A at a SA/V of 100m{sup -1}. Normalized mass losses were calculated for Tc-99 as well as all the major elements in the glass. Results indicated that under ambient oxidizing conditions Tc-99 leached no faster than the glass-forming elements of the glass. In J-13 water, Tc-99 leached congruently with B. In WIPP brine A, it leached congruently with Si. Leach rates for Li were higher in both groundwaters, probably due to a contribution from an ion exchange mechanism. Leach tests were performed under reducing conditions in J-13 water by adding Zn/Hg amalgam to the leachate. In these tests the pH increased significantly, probably because of the reaction of the amalgam with the water. In a 21-day test, the pH increased to 13 and leach rates for the glass were very high. Even though there was signifcant dissolution of the glass, the normalized mass loss based on Tc-99 was only 0.02g/m{sup 2}. This result and the fact that reducing conditions at normal pH values do not significantly affect the dissolution of the glass, indicate that the low concentrations for Tc-99 obtained under reducing conditions are due to is solubility and not due to an increased durability of the glass. 14 refs., 2 figs., 5 tabs
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Compositions and Durabilities of Glasses for Immobilization of Plutonium and Uranium
As the nuclear weapon arsenals of the United States and the Former Soviet Union are reduced, metric tonnage quantities of fissile material must be dispositioned. One of the potential disposition options for fissile weapons material is vitrification into a stable form -- essentially a plutonium or uranium single phase glass product. Savannah River Technology Center (SRTC) at Savannah River Site (SRS) is actively developing suitable glass formulations for the long term safe storage of plutonium and uranium. These investigations are also being extended to develop glasses for the stabilization and storage of kilogram amounts of neptunium, americium, and curium that are currently stored as solutions in the process canyons at SRS -- thus the glasses are called actinide glasses. SRTC is also in the process of developing a remote process demonstration which can produce metric tonnage quantities of the glasses. This paper discusses the chemical compositions and durabilities of two types of actinide glasses under development. One of the glasses is a borosilicate, and the other an iron phosphate. In this initial study thorium and uranium were used as the actinides. Because of the low radioactivity of these elements, the glasses could be prepared and tested on the bench top. In studies beginning in FY `95, glasses containing neptunium, plutonium, americium and curium will be produced. These glasses will be prepared and tested remotely in the shielded cells and glovebox facilities at Savannah River Technology Center. In the initial study, a considerable number (>20) of thorium and uranium bearing glasses have been prepared. An equivalent number of rare earth surrogate (non-radioactive) glasses have also been prepared and tested. The glasses were prepared by mixing dry chemicals and melting them at 1425C for the borosilicate glasses and at 1100C for the iron phosphate glasses. (Abstract Truncated
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Analyses of high-level radioactive glasses and sludges at the Savannah River Site
Reliable analyses of high level radioactive glass and sludge are necessary for successful operation of the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS). This facility will convert the radioactive waste sludges at SRS into durable borosilicate glasses for final disposal in a geologic repository. Analyses that are crucial to DWPF operation and repository acceptance of the glass are measurement of the radioactive and nonradioactive composition of the waste sludges and final glasses and measurement of the Fe(II)/Fe(III) ratio in a vitrified sample of melter feed. These measurements are based on the remote dissolutions of the glass and sludge followed by appropriate chemical analyses. Glasses are dissolved by a peroxide fusion method and a method using HF, HNO{sub 3}, H{sub 3}BO{sub 3}, and HCl acids where the solutions are heated in a microwave oven. The resulting solutions are analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and atomic absorption spectroscopy (AAS) for nonradioactive elements and appropriate counting techniques for radioactive elements. Results for two radioactive glasses containing actual radioactive waste are also presented. Sludges are dissolved by the Na{sub 2}O{sub 2} fusion method and an aqua regia method. 8 refs., 4 tabs
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The effect of gamma irradiation of the volatility and redox state of simulated DWPF high-level nuclear waste glasses
Gamma-induced volatility of simulated DWPF high-level nuclear waste glasses is highly dependent upon the redox state of the glass. For oxidized glasses with an Fe[sup 2+]/(Fe[sup 2+] + Fe[sup 3+]) ratio < 0.1, no volatility was detected after gamma irradiation. Since the projected DWPF high-level radioactive waste glasses will be oxidized, no significant gamma-induced volatility is expected for these glasses upto the glass transition temperature. For larger pieces of highly-reduced DWPF simulated waste glass, no volatility was observed (using [approximately]100 mg pieces in the TGA) after gamma irradiation. However, for powdered samples of this reduced glass, volatility changes upon gamma radiation were detected at 350 and 475[degree]C. The volatility at 350[degree]C was due to changes at the glass surface whereas the change in volatility at 475[degree]C were due to interactions of gamma irradiation within the bulk of the glass. The glass transition temperatures of both oxidized and reduced glasses were unaffected by gamma irradiation but did increase upon a second heat cycle. Results are also presented which reveal that no significant change in redox level within the glass occurred as a result of gamma irradiation
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Investigation of Sludge Batch 3 (Macrobatch 4) Glass Sample Anomalous Behavior
Two Defense Waste Processing Facility (DWPF) glass samples from Sludge Batch 3 (SB3) (Macrobatch 4) were received by the Savannah River National Laboratory (SRNL) on February 23, 2005. One sample, S02244, was designated for the Product Consistency Test (PCT) and elemental and radionuclide analyses. The second sample, S02247, was designated for archival storage. The samples were pulled from the melter pour stream during the feeding of Melter Feed Tank (MFT) Batch 308 and therefore roughly correspond to feed from Slurry Mix Evaporator (SME) Batches 306-308. During the course of preparing sample S02244 for PCT and other analyses two observations were made which were characterized as ''unusual'' or anomalous behavior relative to historical observations of glasses prepared for the PCT. These observations ultimately led to a series of scoping tests in order to determine more about the nature of the behavior and possible mechanisms. The first observation was the behavior of the ground glass fraction (-100 +200 mesh) for PCT analysis when contacted with deionized water during the washing phase of the PCT procedure. The behavior was analogous to that of an organic compound in the presence of water: clumping, floating on the water surface, and crawling up the beaker walls. In other words, the glass sample did not ''wet'' normally, displaying a hydrophobic behavior in water. This had never been seen before in 18 years SRNL PCT tests on either radioactive or non-radioactive glasses. Typical glass behavior is largely to settle to the bottom of the water filled beaker, though there may be suspended fines which result in some cloudiness to the wash water. The typical appearance is analogous to wetting sand. The second observation was the presence of faint black rings at the initial and final solution levels in the Teflon vessels used for the mixed acid digestion of S02244 glass conducted for compositional analysis. The digestion is composed of two stages, and at both the intermediate and the final content levels in the digestion vessel the rings were present. The rings had not been seen previously during glass digestions and were not present in the Analytical Reference Glass (ARG) standard samples digested, in separate vessels, along with the DWPF glass. What follows in this report are the results and analyses from various scoping experiments done in order to explain the anomalous behavior observed with DWPF glass S02244, along with a comparison with tests on sample S02247 where the anomalous wetting behavior was not observed
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Development of Alternative Glass Formulations for Vitrification of Excess Plutonium - SEM/XRD Analyses
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Determination of noble metals in Savannah River Site high-level radioactive sludge
High-level radioactive sludge at the Savannah River Site (SRS) will be processed at the Defense Waste Processing Facility (DWPF) into durable borosilicate glass wasteforms. The sludges are analyzed for elemental content before processing to ensure compatibility with the glass-making processes. Noble metal fission products in sludge, can under certain conditions, cause problems in the glass melter. Therefore, reliable noble metal determinations are important. The scheme used to measure noble metals in SRS sludges consists of dissolving sludge with hot aqua regia followed by determinations with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and ICP-Mass Spectroscopy (ICP-MS) techniques. ICP-MS is the preferred method for measuring trace levels of noble metals in SRS radioactive waste because of superior sensitivity. Analytical results are presented for the two major types of SRS sludge
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EVALUATION OF IMPURITY EXTREMES IN A PLUTONIUM-LOADED BOROSILICATE GLASS
A vitrification technology utilizing a lanthanide borosilicate (LaBS) glass appears to be a viable option for the disposition of excess weapons-useable plutonium that is not suitable for processing into mixed oxide (MOX) fuel. A significant effort to develop a glass formulation and vitrification process to immobilize plutonium was completed in the mid-1990s. The LaBS glass formulation was found to be capable of immobilizing in excess of 10 wt % Pu and to be tolerant of a range of impurities. To confirm the results of previous testing with surrogate Pu feeds containing impurities, four glass compositions were selected for fabrication with actual plutonium oxide and impurities. The four compositions represented extremes in impurity type and concentration. The homogeneity and durability of these four compositions were measured. The homogeneity of the glasses was evaluated using x-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). The XRD results indicated that the glasses were amorphous with no evidence of crystalline species in the glass. The SEM/EDS analyses did show the presence of some undissolved PuO{sub 2} material. The EDS spectra indicated that some of the PuO{sub 2} crystals also contained hafnium oxide. The SEM/EDS analyses showed that there were no heterogeneities in the glass due to the feed impurities. The durability of the glasses was measured using the Product Consistency Test (PCT). The PCT results indicated that the durability of Pu impurity glasses was comparable with Pu glasses without impurities and significantly more durable than the Environmental Assessment (EA) glass used as the benchmark for repository disposition of high-level waste (HLW) glasses
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Hydrogen generation rates in Savannah River Site high-level nuclear waste
High-level nuclear waste (HLW) is stored at the Savannah River Site (SRS) as alkaline, high-nitrate slurries in underground carbon steel tanks. Hydrogen is continuously generated in the waste tanks as a result of the radiolysis of water. Hydrogen generation rates have recently been measured in several waste tanks containing different types of waste. The measured rates ranged from 1.1 to 6.7 cubic feet per million Btu of decay heat. The measured rates are consistent with laboratory data which show that the hydrogen generation rate depends on the nitrate concentration and the decay heat content of the waste. Sampling at different locations indicated that the hydrogen is uniformly distributed radially within the tank
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