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Results of drip tests on sludge-based and actinide-doped glasses

Description: The reaction of three differs simulated nuclear waste glasses is being evaluated using a test method that slowly drips water onto a glass/metal assembly. The tests have been in progress for up to eight years and are being performed with as-cast and glass aged by reaction with water vapor. Results are presented for the cumulative release of Np, Pu, and Am as a function of time; also reported are the particulate species that have been detected suspended in solution. A significant difference is noted in the suspended species depending on the glass composition, and on whether the glass is aged. With as-cast glass, the radioactivity is associated with the suspended particles, while with the aged glass, the solution has a high initial anion content, and the transuranic elements appear to be dissolved in solution, since they pass through filters with small pore sizes. Examples are given of possible tests to evaluate the interaction between these test solutions and potential engineered barrier components.
Date: April 1, 1994
Creator: Bates, J.K. & Buck, E.C.
Partner: UNT Libraries Government Documents Department

Waste glass weathering

Description: The weathering of glass is reviewed by examining processes that affect the reaction of commercial, historical, natural, and nuclear waste glass under conditions of contact with humid air and slowly dripping water, which may lead to immersion in nearly static solution. Radionuclide release data from weathered glass under conditions that may exist in an unsaturated environment are presented and compared to release under standard leaching conditions. While the comparison between the release under weathering and leaching conditions is not exact, due to variability of reaction in humid air, evidence is presented of radionuclide release under a variety of conditions. These results suggest that both the amount and form of radionuclide release can be affected by the weathering of glass.
Date: December 31, 1993
Creator: Bates, J. K. & Buck, E. C.
Partner: UNT Libraries Government Documents Department

Corroded spent nuclear fuel examined with EELS

Description: Samples, exposed to dripping simulated groundwater, were prepared by ultramicrotomy for TEM. The alteration phase was identified as a layered Cs Mo uranyl oxide hydrate, structurally related to phases of the becquerelite group uranium minerals. Second-difference EELS of rare earth elements within the corroded particle detected low levels of TRUs.
Date: July 1, 1996
Creator: Buck, E.C.; Dietz, N.L. & Bates, J.K.
Partner: UNT Libraries Government Documents Department

Colloid formation during waste glass corrosion

Description: The long-term behavior of nuclear waste glass in a geologic repository may require a technical consideration of the role of colloids in the release and transport of radionuclides. The neglect of colloidal properties in assessing the near- and far-field migration behavior of actinides may lead to significant underestimates and poor predictions of biosphere exposure from high-level waste (HLW) disposal. Existing data on colloid-facilitated transport suggests that radionuclide migration may be enhanced, but the importance of colloids is not adequately assessed. Indeed, the occurrence of radionuclide transport, attributed to colloidal species, has been reported at Mortandad Canyon, Los Alamos and at the Nevada Test Site; both unsaturated regions are similar to the proposed HLW repository at Yucca Mountain. Although some developments have been made on understanding the transport characteristics of colloids, the characterization of colloids generated from the corrosion of the waste form has been limited. Colloids are known to incorporate radionuclides either from hydrolysis of dissolved species (real colloids) or from adsorption of dissolved species onto existing groundwater colloids (pseudocolloids); however, these colloids may be considered secondary and solubility limited when compared to the colloids generated during glass alteration.
Date: May 1, 1996
Creator: Mertz, C.J.; Buck, E.C.; Fortner, J.A. & Bates, J.K.
Partner: UNT Libraries Government Documents Department

Microscopic analysis of Pu-contaminated incinerator ash: Implications for immobilization

Description: In this paper, a nanometer-scale mineralogical study with analytical transmission electron microscopy (AEM) of plutonium-bearing incinerator ash from the Rocky Flats Environmental Technology Site (RFETS) in Colorado is described. The findings from this work may have implications for the present effort to immobilize plutonium waste. Around 70% of the plutonium ash in the DOE weapons complex is stored at RFETS. The ash was formed from the combustion of contaminated wastes generated from plutonium processing. The RFETS incinerator ash composition has been determined by Blum et al. The ash was formed at temperatures estimated to be between 200 C and 900 C and contains up to 14 wt% Pu. Ash is a generic term used to describe the by-product of combustion and owing to the variability in the inorganic components.
Date: October 1, 1997
Creator: Buck, E.C.
Partner: UNT Libraries Government Documents Department

The behavior of silicon and boron in the surface of corroded nuclear waste glasses : an EFTEM study.

Description: Using electron energy-loss filtered transmission electron microscopy (EFTEM), we have observed the formation of silicon-rich zones on the corroded surface of a West Valley (WV6) glass. This layer is approximately 100-200 nm thick and is directly underneath a precipitated smectite clay layer. Under conventional (C)TEM illumination, this layer is invisible; indeed, more commonly used analytical techniques, such as x-ray energy dispersive spectroscopy (EDS), have failed to describe fully the localized changes in the boron and silicon contents across this region. Similar silicon-rich and boron-depleted zones were not found on corroded Savannah River Laboratory (SRL) borosilicate glasses, including SRL-EA and SRL-51, although they possessed similar-looking clay layers. This study demonstrates a new tool for examining the corroded surfaces of materials.
Date: November 23, 1999
Creator: Buck, E. C.; Smith, K. L. & Blackford, M. G.
Partner: UNT Libraries Government Documents Department

Retention of neptunium in uranyl alteration phases formed during spent fuel corrosion

Description: Uranyl oxide hydrate phases are known to form during contact of oxide spent nuclear fuel with water under oxidizing conditions; however, less is known about the fate of fission and neutron capture products during this alteration. We describe, for the first time, evidence that neptunium can become incorporated into the uranyl secondary phase, dehydrated schoepite (UO{sub 3}.8H{sub 2}O). Based on the long term durability of natural schoepite, the retention of neptunium in this alteration phase may be significant during spent fuel corrosion in an unsaturated geologic repository.
Date: September 1, 1997
Creator: Buck, E.C.; Finch, R.J.; Finn, P.A. & Bates, J.K.
Partner: UNT Libraries Government Documents Department

Potential incorporation of transuranics into uranium phases

Description: The UO{sub 2} in spent nuclear fuel is unstable under moist oxidizing conditions and will be altered to uranyl oxide hydrate phases. The transuranics released during the corrosion of spent fuel may also be incorporated into the structures of secondary U{sup 6+} phases. The incorporation of radionuclides into alteration products will affect their mobility. A series of precipitation tests were conducted at either 150 or 90 C for seven days to determine the potential incorporation of Ce{sup 4+} and Nd{sup 3+} (surrogates for Pu{sup 4+} and Am{sup 3+}, respectively) into uranium phases. Ianthinite ([U{sub 2}{sup 4+}(UO{sub 2}){sub 4}O{sub 6}(OH){sub 4}(H{sub 2}O){sub 4}](H{sub 2}O){sub 5}) was produced by dissolving uranium oxyacetate in a solution containing copper acetate monohydrate as a reductant. The leachant used in these tests were doped with either 2.1 ppm cerium or 399 ppm neodymium. Inductively coupled plasma-mass spectrometer (ICP-MS) analysis of the solid phase reaction products which were dissolved in a HNO{sub 3} solution indicates that about 306 ppm Ce (K{sub d} = 146) was incorporated into ianthinite, while neodymium contents were much higher, being approximately 24,800 ppm (K{sub d} = 62). Solid phase examinations using an analytical transmission electron microscope/electron energy-loss spectrometer (AEM/EELS) indicate a uniform distribution of Nd, while Ce contents were below detection. Becquerelite (Ca[(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}]{center_dot}8H{sub 2}O) was produced by dissolving uranium oxyacetate in a solution containing calcium acetate. The leachant in these tests was doped with either 2.1 ppm cerium or 277 ppm neodymium. ICP-MS results indicate that about 33 ppm Ce (K{sub d}=16) was incorporated into becquerelite, while neodymium contents were higher, being approximately 1,300 ppm (K{sub d}=5). Homogeneous distribution of Nd in the solid phase was noted during AEM/EELS examination, and Ce contents were also below detection.
Date: December 7, 1999
Creator: Kim, C. W.; Wronkiewicz, D. J. & Buck, E. C.
Partner: UNT Libraries Government Documents Department

Analytical electron microscopy characterization of Fernald soils. Annual report, October 1993--September 1994

Description: A combination of backscattered electron imaging and analytical electron microscopy (AEM) with electron diffraction have been used to determine the physical and chemical properties of uranium contamination in soils from the Fernald Environmental Management Project in Ohio. The information gained from these studies has been used in the development and testing of remediation technologies. Most chemical washing techniques have been reasonably effective with uranyl [U(VI)] phases, but U(IV) phases have proven difficult to remove from the soils. Carbonate leaching in an oxygen environment (heap leaching) has removed some of the U(IV) phases, and it appears to be the most effective technique developed in the program. The uranium metaphosphate, which was found exclusively at an incinerator site, has not been removed by any of the chemical methods. We suggest that a physical extraction procedure (either a magnetic separation or aqueous biphasic process) be used to remove this phase. Analytical electron microscopy has also been used to determine the effect of the chemical agents on the uranium phases. It has also been used to examine soils from the Portsmouth site in Ohio. The contamination there took the form of uranium oxide and uranium calcium oxide phases. Technology transfer efforts over FY 1994 have led to industry-sponsored projects involving soil characterization.
Date: March 1, 1995
Creator: Buck, E.C.; Brown, N.R. & Dietz, N.L.
Partner: UNT Libraries Government Documents Department

Nuclear Waste Programs semiannual progress report, April--September 1992

Description: This document reports on the work done by the Nuclear Waste Programs of the Chemical Technology Division (CMT), Argonne National Laboratory, in the period April--September 1992. In these programs, studies are underway on the performance of waste glass and spent fuel in projected nuclear repository conditions to provide input to the licensing of the nation`s high-level waste repositories.
Date: May 1, 1994
Creator: Bates, J.K.; Bradley, C.R. & Buck, E.C.
Partner: UNT Libraries Government Documents Department

Incorporation of radionuclides in the alteration phases of spent nuclear fuel.

Description: Alteration may be expected for spent nuclear fuel exposed to groundwater under oxidizing conditions such as that which exist at the proposed nuclear waste repository at Yucca Mountain, Nevada. The actinide elements released during the corrosion of spent fuel may be incorporated into the structures of secondary U{sup 6+} phases. The incorporation of transuranics into the crystal structures of the alteration products may significantly decrease their mobility. A series of precipitation tests were conducted at 90 C to determine the potential incorporation of Ce{sup 4+} and Nd{sup 3+} (surrogates for Pu{sup 4+} and Am{sup 3+}, respectively) into uranyl phase. Dehydrated schoepite (UO{sub 3}{center_dot}0.8-1.0HP{sub 2}O) was produced by hydrolysis of a uranium oxyacetate solution containing either cerium or neodymium. ICP-MS analysis of the leachant, leachate, and solid phase reaction products which were dissolved in a HNO{sub 3} solution indicates that 26 ppm of Ce was incorporated into dehydrated schoepite. ICP-MS results from the Nd-doped tests indicate significant neodymium incorporation as well, however, the heterogeneous distribution of Nd in the solid phase noted during the AEM/EELS examination implies that neodymium may not incorporate into the structure of dehydrated schoepite.
Date: August 25, 1999
Creator: Buck, E. C.; Kim, C.-W. & Wronkiewicz, D. J.
Partner: UNT Libraries Government Documents Department

The reaction of SRL 202 glass in J-13 and DIW

Description: Static leach tests were performed in both 304L stainless steel and Teflon vessels using a synthetic high-level waste glass with either deionized water (DIW) or a tuff groundwater solution as the leachant to assess the effects of the vessel and the initial leachant composition on the extent and nature of the glass reaction. The tests were performed using monolith samples at 340 m{sup {minus}1} and crushed samplesat 2000 m{sup {minus}1} for times up to 1 year. The results show less silicon is released from the glass into the groundwater solution than into DIW at both high and low glass surface area/leachant volume ratios (SAN), but the alkali metal and boron releases are not affected by the leachant used. Tests performed in a stainless steel vessel resulted in slightly lower leachate pH values, but similar reaction rates to those performed in a Teflon vessel, as measured by the boron release. Blank tests with DIW or EJ-13 in the vessels showed the Teflon vessels to release small amounts of fluoride (1 to 2 ppm) and to acidify the DIW slightly (4.0 < pH < 5.6). The pH values of blank tests with EJ- 1 3 increased from 8.2 to about 8.6 in steel and to about 9.2 in Teflon vessels. The slightly higher pH values attained in Teflon vessels are attributed to outgassing of CO{sub 2} during the test.
Date: December 31, 1992
Creator: Ebert, W.L.; Bates, J.K. & Buck, E.C.
Partner: UNT Libraries Government Documents Department

ANL technical support program for DOE environmental restoration and waste management. Annual report, October 1993--September 1994

Description: A program was established for DOE Environmental Restoration and Waste Management (EM) to evaluate factors that are anticipated to affect waste glass reaction during repository disposal, especially in an unsaturated environment typical of what may be expected for the proposed Yucca Mountain repository site. This report covers progress in FY 1994 on the following tasks: (1) Critical Reviews of important parameters that affect the reactivity of glass in an unsaturated environment are being prepared. (2) A series of tests is ongoing to evaluate the reactivity of fully radioactive glasses in a high-level waste repository environment and compare it to the reactivity of synthetic, nonradioactive glasses of similar composition. (3) The effect of radiation upon the durability of waste glasses at a high SA/V ratio and a high gas-to-liquid volume ratio has been assessed. (4) A series of tests is being performed to compare the extent of reaction of nuclear waste glasses at various SA/V ratios. Such differences in the SA/V ratio may significantly affect glass durability. At long-term periods and high SA/V ratios, acceleration in glass reaction has been observed. (5) Tests were initiated on West Valley Reference 6 (WV6) glass and on the Environmental Assessment (EA) glass. (6) Tests with the actinide-doped West Valley glass ATM-10 have been in progress for over seven years as a part of work for the Yucca Mountain Site Characterization Project (YMP). (7) Analytical electron microscopy (AEM) is being used to assess the glass/water reaction pathway by identifying intermediate phases that appear on the reacting glass. Also, colloids from the leach solutions are being studied using AEM.
Date: June 1, 1995
Creator: Bates, J.K.; Brown, N.R. & Buck, E.C.
Partner: UNT Libraries Government Documents Department

Analytical Electron Microscopy Characterization of Fernald soils. Annual Report, October 1993 - September 1994

Description: A combination of backscattered electron imaging and analytical electron microscopy (AEM) with electron diffraction have been used to determine the physical and chemical properties of uranium contamination in soils from the Fernald Environmental Management Project in Ohio. The information gained from these studies has been used in the development and testing of remediation technologies.
Date: March 1995
Creator: Buck, E. C.; Brown, N. R. & Dietz, N. L.
Partner: UNT Libraries Government Documents Department

Spent fuel`s behavior under dynamic drip tests

Description: In the potential repository at Yucca Mountain, failure of the waste package container and the cladding of the spent nuclear fuel would expose the fuel to water under oxidizing conditions. To simulate the release behavior of radionuclides from spent fuel, dynamic drip and vapor tests with spent nuclear fuel have been ongoing for 2.5 years. Rapid alteration of the spent fuel has been noted with concurrent release of radionuclides. Colloidal species containing americium and plutonium have been found in the leachate. This observation suggests that colloidal transport of radionuclides should be included in the performance assessment of a potential repository.
Date: December 1, 1995
Creator: Finn, P.A.; Buck, E.C.; Hoh, J.C. & Bates, J.K.
Partner: UNT Libraries Government Documents Department

Initial comparison of leach behavior between fully radioactive and simulated nuclear waste glass through long-term testing: Part 2, Reacted layer analysis

Description: An initial comparison of glass behavior of simulated nuclear waste glasses has been made through long-term testing of general glass types SRL165, SRL131 and SRL200. The data demonstrate that up to 560 days at S/V of 2000/m, the reacted layers consist of one outer clay layer, which is undetermined by discontinuous etch pits. The regions between the etch pits are alkali depleted. The surface layer becomes thicker as test duration progresses and the reacted layer after the same test time is thinner at higher S/V than at lower S/V. The relative glass durability measured by the thickness of the reacted layer is 165/42S > 131/11S > 200S, which is consistent with solution analyses. In general, the reacted layers on all glass compositions are poorly crystallized which makes the clay identification difficult. The diffraction spacings and EDS compositions for 131/11S and 200S, although not unique to, are consistent with Na (or Ca-) montmorillonite or nontronite. Both of these are dioctahedral smectite.
Date: January 1, 1992
Creator: Bates, J.K.; Feng, X.; Bradley, C.R. & Buck, E.C.
Partner: UNT Libraries Government Documents Department

Uranium-contaminated soils: Ultramicrotomy and electron beam analysis

Description: Uranium-contaminated soils from the U.S. Department of Energy (DOE) Fernald Site, Ohio, have been examined by a combination of scanning electron microscopy with backscattered electron imaging (SEM/BSE) and analytical electron microscopy (AEM). The inhomogeneous distribution of particulate uranium phases in the soil required the development of a method for using ultramicrotomy to prepare transmission electron microscopy (TEM) thin sections of the SEM mounts. A water-miscible resin was selected that allowed comparison between SEM and TEM images, permitting representative sampling of the soil. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite (UO{sub 2}). No uranium was detected in association with phyllosilicates in the soil.
Date: February 1, 1994
Creator: Buck, E. C.; Dietz, N. L.; Bates, J. K. & Cunnane, J. C.
Partner: UNT Libraries Government Documents Department

Accelerated glass reaction under PCT conditions

Description: Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.
Date: January 1, 1992
Creator: Ebert, W.L.; Bates, J.K.; Buck, E.C. & Bradley, C.R.
Partner: UNT Libraries Government Documents Department

Analytical Electron Microscopy examination of uranium contamination at the DOE Fernald operation site

Description: Analytical Electron Microscopy (AEM) has been used to identify uranium-bearing phases present in contaminated soils from the DOE Fernald operation site. A combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and AEM was used in isolating and characterizing uranium-rich regions of the contaminated soils. Soil samples were prepared for transmission electron microscopy (TEM) by ultramicrotomy using an embedding resin previously employed for aquatic colloids and biological samples. This preparation method allowed direct comparison between SEM and TEM images. At the macroscopic level much of the uranium appears to be associated with clays in the soils; however, electron beam analysis revealed that the uranium is present as discrete phases, including iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Only low levels of uranium were actually within the clay minerals. The distribution of uranium phases was inhomogeneous at the submicron level.
Date: February 1, 1993
Creator: Buck, E.C.; Dietz, N.L.; Bates, J.K. & Cunnane, J.C.
Partner: UNT Libraries Government Documents Department

Does fully radioactive glass behave differently than simulated waste glass?

Description: There has been interest in the comparison of the leach behavior between fully radioactive and simulated nuclear waste glasses, to assess the differences in reaction mechanism, type, and sequence of secondary phases, and the relative durability among the two types of glasses. The results from these comparisons will provide confidence in the use of the large amount of the data generated in the studies of simulated nuclear waste glass for the modeling of performance of radioactive glasses. Most of the previous comparison studies have been performed at a low to intermediate ratio of glass surface area to solution volume and for time periods of less than one year. These studies have generally concluded there is a little difference in leach behavior between the two glass types. This study reinvestigates that conclusion by utilizing an extensive test matrix, with SA/V ranging between 340 to 20,000 m{sup 1} on three waste glass compositions, for time periods planned up to eight years. The early results are consistent with other studies, in that the leach behavior of simulated waste glasses is similar to that of fully radioactive glasses. However, the longer-term tests at higher SA/V suggest that the leach behavior of the two types of glass diverges, under certain conditions. The longer-term comparison of the leach behavior is discussed.
Date: December 31, 1992
Creator: Feng, X.; Bates, J. K.; Bradley, C. R. & Buck, E. C.
Partner: UNT Libraries Government Documents Department

Distribution of uranium-bearing phases in soils from Fernald

Description: Electron beam techniques have been used to characterize uranium-contaminated soils and the Fernald Site, Ohio. Uranium particulates have been deposited on the soil through chemical spills and from the operation of an incinerator plant on the site. The major uranium phases have been identified by electron microscopy as uraninite, autunite, and uranium phosphite [U(PO{sub 3}){sub 4}]. Some of the uranium has undergone weathering resulting in the redistribution of uranium within the soil.
Date: December 31, 1993
Creator: Buck, E. C.; Brown, N. R. & Dietz, N. L.
Partner: UNT Libraries Government Documents Department

Does fully radioactive glass behave differently than simulated waste glass

Description: There has been interest in the comparison of the leach behavior between fully radioactive and simulated nuclear waste glasses, to assess the differences in reaction mechanism, type, and sequence of secondary phases, and the relative durability among the two types of glasses. The results from these comparisons will provide confidence in the use of the large amount of the data generated in the studies of simulated nuclear waste glass for the modeling of performance of radioactive glasses. Most of the previous comparison studies have been performed at a low to intermediate ratio of glass surface area to solution volume and for time periods of less than one year. These studies have generally concluded there is a little difference in leach behavior between the two glass types. This study reinvestigates that conclusion by utilizing an extensive test matrix, with SA/V ranging between 340 to 20,000 m[sup 1] on three waste glass compositions, for time periods planned up to eight years. The early results are consistent with other studies, in that the leach behavior of simulated waste glasses is similar to that of fully radioactive glasses. However, the longer-term tests at higher SA/V suggest that the leach behavior of the two types of glass diverges, under certain conditions. The longer-term comparison of the leach behavior is discussed.
Date: January 1, 1992
Creator: Feng, X.; Bates, J.K.; Bradley, C.R. & Buck, E.C.
Partner: UNT Libraries Government Documents Department

Uranium-contaminated soils: Ultramicrotomy and electron beam analysis

Description: Uranium contaminated soils from the Fernald Operation Site, Ohio, have been examined by a combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM). A method is described for preparing of transmission electron microscopy (TEM) thin sections by ultramicrotomy. By using these thin sections, SEM and TEM images can be compared directly. Uranium was found in iron oxides, silicates (soddyite), phosphates (autunites), and fluorite. Little uranium was associated with clays. The distribution of uranium phases was found to be inhomogeneous at the microscopic level.
Date: April 1, 1994
Creator: Buck, E. C.; Dietz, N. L.; Bates, J. K. & Cunnane, J. C.
Partner: UNT Libraries Government Documents Department

Colloid formation during the corrosion of SRL 200 glass

Description: Nonradioactive SRL 200S glass and fully radioactive SRL 200R glass were reacted at glass surface areas to leachant volume (SA/V) ratios of 20,000, 2,000, and 340 m{sup {minus}1} for times varying from several days to a few years. The particles present in the leachates of these tests have been examined by analytical electron microscopy (AEM). The major colloidal clay phase was identified as a smectite clay from its characteristic electron diffraction pattern. The clay colloids eventually disappear from the solution and return to the glass; the time at which this occurs depends on the SA/V. Uranium silicate particles and calcium-bearing phases were also sometimes found in the leachates.
Date: May 1, 1994
Creator: Buck, E. C.; Bates, J. K. & Feng, X.
Partner: UNT Libraries Government Documents Department