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Production of a High-Level Waste Glass from Hanford Waste Samples

Description: The HLW glass was produced from a HLW sludge slurry (Envelope D Waste), eluate waste streams containing high levels of Cs-137 and Tc-99, solids containing both Sr-90 and transuranics (TRU), and glass-forming chemicals. The eluates and Sr-90/TRU solids were obtained from ion-exchange and precipitation pretreatments, respectively, of other Hanford supernate samples (Envelopes A, B and C Waste). The glass was vitrified by mixing the different waste streams with glass-forming chemicals in platinum/gold crucibles and heating the mixture to 1150 degree C. Resulting glass analyses indicated that the HLW glass waste form composition was close to the target composition. The targeted waste loading of Envelope D sludge solids in the HLW glass was 30.7 wt percent, exclusive of Na and Si oxides. Condensate samples from the off-gas condenser and off-gas dry-ice trap indicated that very little of the radionuclides were volatilized during vitrification. Microstructure analysis of the HLW glass using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDAX) showed what appeared to be iron spinel in the HLW glass. Further X-Ray Diffraction (XRD) analysis confirmed the presence of nickel spinel trevorite (NiFe2O4). These crystals did not degrade the leaching characteristics of the glass. The HLW glass waste form passed leach tests that included a standard 90 degree C Product Consistency Test (PCT) and a modified version of the United States Environmental Protection Agency Toxicity Characteristic Leaching Procedure (TCLP).
Date: September 1998
Creator: Crawford, C. L.; Farrara, D. M.; Ha, B. C. & Bibler, N. E.
Partner: UNT Libraries Government Documents Department

4.5 Meter high level waste canister study

Description: The Tank Waste Remediation System (TWRS) Storage and Disposal Project has established the Immobilized High-Level Waste (IBLW) Storage Sub-Project to provide the capability to store Phase I and II BLW products generated by private vendors. A design/construction project, Project W-464, was established under the Sub-Project to provide the Phase I capability. Project W-464 will retrofit the Hanford Site Canister Storage Building (CSB) to accommodate the Phase I I-ILW products. Project W-464 conceptual design is currently being performed to interim store 3.0 m-long BLW stainless steel canisters with a 0.61 in diameter, DOE is considering using a 4.5 in canister of the same diameter to reduce permanent disposal costs. This study was performed to assess the impact of replacing the 3.0 in canister with the 4.5 in canister. The summary cost and schedule impacts are described.
Date: October 1, 1997
Creator: Calmus, R.B., Westinghouse Hanford, Richland, WA
Partner: UNT Libraries Government Documents Department

Evaporator Cleaning Studies

Description: Operation of the 242-16H High Level Waste Evaporator proves crucial to liquid waste management in the H-Area Tank Farm. Recent operational history of the Evaporator showed significant solid formation in secondary lines and in the evaporator pot. Additional samples remain necessary to ensure material identity in the evaporator pot. Analysis of these future samples will provide actinide partitioning information and dissolution characteristics of the solid material from the pot to ensure safe chemical cleaning.
Date: April 15, 1999
Creator: Wilmarth, W.R.
Partner: UNT Libraries Government Documents Department

Microstructural properties of high level waste concentrates and gels with raman and infrared spectroscopies. 1997 annual progress report

Description: 'Monosodium aluminate, the phase of aluminate found in waste tanks, is only stable over a fairly narrow range of water vapor pressure (22% relative humidity at 22 C). As a result, aluminate solids are stable at Hanford (seasonal average RH {approximately}20%) but are not be stable at Savannah River (seasonal average RH {approximately}40%). Monosodium aluminate (MSA) releases water upon precipitation from solution. In contrast, trisodium aluminate (TSA) consumes water upon precipitation. As a result, MSA precipitates gradually over time while TSA undergoes rapid accelerated precipitation, often gelling its solution. Raman spectra reported for first time for monosodium and trisodium aluminate solids. Ternary phase diagrams can be useful for showing effects of water removal, even with concentrated waste. Kinetics of monosodium aluminate precipitation are extremely slow (several months) at room temperature but quite fast (several hours) at 60 C. As a result, all waste simulants that contain aluminate need several days of cooking at 60 C in order to truly represent the equilibrium state of aluminate. The high level waste (HLW) slurries that have been created at the Hanford and Savannah River Sites over that last fifty years constitute a large fraction of the remaining HLW volumes at both sites. In spite of the preponderance of these wastes, very little quantitative information is available about their physical and chemical properties other than elemental analyses.'
Date: 1997-23~
Creator: Agnew, S.F.; Coarbin, R.A. & Johnston, C.T.
Partner: UNT Libraries Government Documents Department

Enhanced sludge processing of HLW: Hydrothermal oxidation of chromium, technetium, and complexants by nitrate. 1998 annual progress report

Description: 'The objective of this project is to develop the scientific basis for hydrothermal separation of chromium from High Level Waste (HLW) sludges. The worked is aimed at attaining a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions that will ultimately lead to an efficient chromium leaching process. This report summarizes the research over the first 1.5 years of a 3 year project. The authors have examined the dissolution of chromium hydroxide using different oxidants as a function of temperature and alkalinity. The results and possible applications to HLW sludges are discussed'
Date: June 1, 1998
Creator: Buelow, S.J. & Robinson, J.M.
Partner: UNT Libraries Government Documents Department

Microstructural properties of high level waste concentrates and gels with raman And infrared spectroscopies. 1998 annual progress report

Description: 'The concentrated caustic waste slurries stored in waste tanks at Hanford and Savannah River have large amounts of aluminate along with nitrate, nitrite, hydroxide, carbonate, and phosphate-all species are present both in solution and as solids. The dominant cation is sodium with few percent potassium and other species. These slurries have sodium concentrations on the order of 10--15 mol/L and therefore very high ionic strengths and low water activities. These slurries have been the source of many safety problems at Hanford and Savannah River Sites and the slurry rheologies, gelling points, and gas retention properties are largely responsible for those safety issues. Even though both Hanford and Savannah River have produced large volumes of these slurry concentrates, the microstructural properties that are important for understanding slurry behavior are not well understood. For example, aluminate solid formation has been associated with Hanford concentrates, but is not observed at Savannah River. Another example is that although hydrogen gas retention in slurries is a prevailing safety issue at Hanford, it is only a relatively minor issue in SRS tanks.'
Date: June 1, 1998
Creator: Agnew, S.F. & Johnston, C.T.
Partner: UNT Libraries Government Documents Department

Particle generation by laser ablation in support of chemical analysis of high level mixed waste from plutonium production operations. 1998 annual progress report

Description: 'The authors goal is to provide fundamental mechanistic studies of laser produced particulate formation in support of the use of Laser Assisted-Inductively Coupled Plasma-Mass Spectroscopy (LA-ICP-MS) to be used for analysis of radioactive/toxic materials. The work reported here represents the first nine months of this 3-year project. The major focus of these studies is determining the detailed mechanisms and character of the particulates generated by laser ablation of solid targets relevant to sampling materials for chemical analysis using inductively coupled mass spectroscopy, ICP-MS. In this application, particles generated by laser ablation must be transported to the plasma torch of the ICP-MS, often through a hollow tube with an interior diameter of a few mm. Proper digestion and ionization of particles in the plasma limits particle sizes to under a micron. Thus the production of submicron particles which truly represent the stoichiometry of the specimen is of critical importance.'
Date: June 1, 1998
Creator: Dickinson, J.T. & Alexander, M.L.
Partner: UNT Libraries Government Documents Department

Radiation effects on materials in the near-field of nuclear waste repository. 1998 annual progress report

Description: 'Site restoration activities at DOE facilities and the permanent disposal of nuclear waste generated at DOE facilities involve working with and within various types and levels of radiation fields. Once the nuclear waste is incorporated into a final form, radioactive decay will decrease the radiation field over geologic time scales, but the alpha-decay dose for these solids will still reach values as high as 10{sup 18} alpha-decay events/gm in periods as short as 1,000 years. This dose is well within the range for which important chemical (e.g., increased leach rate) and physical (e.g., volume expansion) changes may occur in crystalline ceramics. Release and sorption of long-lived actinides (e.g., {sup 237}Np) can provide a radiation exposure to backfill materials, and changes in important properties (e.g., cation exchange capacity) may occur. The objective of this research program is to evaluate the long term radiation effects in the materials in the near-field of a nuclear waste repository with accelerated experiments in the laboratory using energetic particles (electrons, ions and neutrons). Experiments on the microstructural evolution during irradiation of two important groups of materials, sheet silicates (e.g., clays) and zeolites (analcime), have been conducted; and studies of radiation-induced changes in chemical properties (e.g. cation exchange capacity) are underway. As of the mid-2nd year of the 3-year project, experiments on the microstructural evolution during irradiation of two important group of materials, sheet silicates (mica) and zeolites (analcime), have been conducted; and studies of radiation-induced changes in chemical properties (e.g., cation exchange capacity) are underway.'
Date: June 1, 1998
Creator: Wang, L.M. & Ewing, R.C.
Partner: UNT Libraries Government Documents Department

Mechanism of pitting corrosion prevention by nitrite in carbon steel exposed to dilute salt solutions. 1998 annual progress report

Description: 'The overall goal of this project is to develop a fundamental understanding of the role of nitrite in preventing the breakdown of protective oxide(s) on carbon steel and the onset of pitting. Pitting corrosion of carbon steel exposed to dilute alkaline salt solutions can be induced by nitrate, sulfate, and chloride ions and is prevented by sufficient concentration of nitrite. A significant example of this material/electrolyte system is the storage and processing of DOE''s high-level radioactive liquid waste in carbon steel tanks. Added nitrite in the waste has a considerable downstream impact on the immobilization of the waste in a stable glass form. Waste tank integrity and glass production efficiency may benefit from the fundamental understanding of nitrite''s role in preventing pitting. This report summarizes progress after approximately six months of effort in this three-year EMSP project. Initial experimental and theoretical work has focused on the electrochemical behavior of carbon steel in simplified non-radioactive solutions that simulate complex dilute radioactive waste solutions. These solutions contain corrosion-inducing species such as nitrate and chloride and the corrosion-inhibiting nitrite at moderately alkaline pHs. The electrochemical behavior of interest here is that of the open-circuit potential of the steel specimen at equilibrium in the experimental electrolyte and the measures of the steel''s passivity and passivity breakdown.'
Date: June 1, 1998
Creator: Zapp, P.E. & Zee, J. van
Partner: UNT Libraries Government Documents Department

Optically-based array sensors for selective in situ analysis of tank waste. 1998 annual progress report

Description: 'The objective of this research program is to conduct the fundamental research necessary to develop an array of chemically selective sensors, based on highly selective molecular recognition agents and highly sensitive fluorescence and/or phosphorescence techniques, that can be coupled to fiber optics for remote analytical applications. These sensors will be of great value to DOE for the safe and cost-effective in situ characterization of high level waste tanks. Characterization of high level tank waste currently entails obtaining and analyzing core samples at the cost of about $1 million per sample. The ability to detect and measure specific chemicals and radionuclides directly inside a high level waste tank using a remote sensing device could result in considerable benefits with regard to both cost savings and safety issues. This multidisciplinary approach to the design of sensors will be to immobilize agents for selective molecular recognition, chosen from solvent extraction processes, in an organic polymer matrix that mimics the organic medium in an aqueous-nonaqueous extraction. In this manner the matrix will enhance both the separation and the achievement of chemical selectivity. Good progress has been made in the first nine months of this project. Calix[4]bis-crown-6-ethers in the 1,3-alternate conformation have been shown to possess a high degree of selectivity for cesium over sodium (Cs/Na selectivity > 104 in selected diluents), and moderate selectivity over potassium (Cs/K selectivity of about 102 in selected diluents). The work has involved the preparation of a new class of calixarene-based ionophores. Of particular interest within this class of compounds are various derivatives of calix[4]arene-crown-4, -crown-5, and -crown-6 ionophores, possessing high selectivities for sodium, potassium, and cesium, respectively. The goal is to synthetically modify the ionophore by attaching a fluorescent probe molecule to the crown ring in such a manner that fluorescence is normally quenched by photoinduced electron transfer ...
Date: June 1, 1998
Creator: Brown, G.M.; Dabestani, R.; Bonnesen, P.V. & Walt, D.R.
Partner: UNT Libraries Government Documents Department

The NOx system in nuclear waste. 1997 annual progress report

Description: 'The authors highlight their results from the title project. The project is a coordinated effort of the three Co-PIs to assist the Safety Programs at the Hanford and other DOE Environmental Management Sites. The authors present in the report their observations and interactively discuss their implications for safety concerns. They focus on three issues: (1) Reducing radicals in the NOx system The authors show that the only reducing radical that lasts longer than a few ns in typical waste solutions, and is capable of generating hydrogen, is NO{sub 3}{sup 2-}. The authors measured the lifetime of this species across the whole pH range (3 {le} pH {le} 14) and found it to be shorter than -15 \265s, before it dissociates to give the strongly oxidizing NO, radicals. They found that it reacts with many proton donors (H{sup +}, phosphate, borate, NH{prime}, amines) in a reaction that is not merely an acid-base equilibrium reaction but is probably a dissociative proton transfer. They estimate the redox potential from theoretical considerations and obtain an experimental verification. They conclude that it is highly unlikely, although thermodynamically possible, that this radi-cal will generate hydrogen in waste solutions. (2) Aging of organic chelators and their degradation products by NO, Methodologies to study the degradation of organic substrates (including the important waste components, formate and oxalate) to CO;, or carbonate, by NO, were developed. This radical dimerizes and disproportionates to nitrate and nitrite. Therefore, mineraliza-tion of the organic substrates competes with the disproportionation of NO,. Among the organic substrates, formate and oxalate are also mineralized but because they are of low fuel value their mineralization is not very helpful, yet it consumes NO,. (3) Interfacial processes in aqueous suspensions Yields of charge transfer from solid silica particles to water and other liquids were meas-ured. If the particles ...
Date: January 1, 1997
Creator: Meisel, D.; Camaioni, D. & Orlando, T.
Partner: UNT Libraries Government Documents Department

Interfacial radiolysis effects in tank waste speciation. 1998 annual progress report

Description: 'The purpose of this program is to deliver pertinent, fundamental information that can be used to make technically defensible decisions on safety issues and processing strategies associated with storage and clean up of DOE mixed chemical and radioactive wastes. The radioactive and chemical wastes present in DOE underground storage tanks contain complex mixtures of sludges, salts, and supernatant liquids. These mixtures, which contain a wide variety of oxide materials, aqueous solvents, and organic components, are constantly bombarded with gamma quanta, beta and alpha particles produced via the decay of radioactive isotopes. Currently, there is a vital need to understand radiolysis of organic and inorganic species present in mixed waste tanks because these processes: (a) produce mixtures of toxic, flammable, and potentially explosive gases (i.e., H{sub 2}, N{sub 2}O and volatile organics) (b) degrade organics, possibly to gas-generating organic fragments, even as the degradation reduces the hazards associated with nitrate-organic mixtures, (c) alter the surface chemistry of insoluble colloids in tank sludge, influencing sedimentation and the gas/solid interactions that may lead to gas entrapment phenomena. This report summarizes the technical achievements of a 3-year project that is now in its 2nd year. Progress in three areas is reported: (1) radiation effects at NaNO 3 crystal interfaces, (2) reactions of organic complexants with NO{sub 2} in water, and (3) radiation effects in oxide particles.'
Date: June 1, 1998
Creator: Orlando, T. M.; Camaioni, D. & Meisel, D.
Partner: UNT Libraries Government Documents Department

Development of advanced electrochemical emission spectroscopy for monitoring corrosion in simulated DOE liquid waste. 1998 annual progress report

Description: 'Objective of this project is to develop and use Electrochemical Emission Spectroscopy (EES) and other electrochemical techniques as in situ tools for exploring corrosion mechanisms of iron and carbon steel in highly alkaline solutions and for continuously monitoring corrosion on structural materials in DOE liquid waste storage system. In particular, the author will explore the fundamental aspects of the passive behavior of pure iron since breakdown of passivity leads to localized corrosion. This report summarizes work after 1 year of a 3 year project.'
Date: June 1, 1998
Creator: MacDonald, D.D.
Partner: UNT Libraries Government Documents Department

Enhanced sludge processing of HLW: Hydrothermal oxidation of chromium, technetium, and complexants by nitrate. 1997 mid-year progress report

Description: 'Treatment of High Level Waste (HLW) is the second most costly problem identified by OEM. In order to minimize costs of disposal, the volume of HLW requiring vitrification and long term storage must be reduced. Methods for efficient separation of chromium from waste sludges, such as the Hanford Tank Wastes (HTW), are key to achieving this goal since the allowed level of chromium in high level glass controls waste loading. At concentrations above 0.5 to 1.0 wt.% chromium prevents proper vitrification of the waste. Chromium in sludges most likely exists as extremely insoluble oxides and minerals, with chromium in the plus III oxidation state [1]. In order to solubilize and separate it from other sludge components, Cr(III) must be oxidized to the more soluble Cr(VI) state. Efficient separation of chromium from HLW could produce an estimated savings of $3.4B[2]. Additionally, the efficient separation of technetium [3], TRU, and other metals may require the reformulation of solids to free trapped species as well as the destruction of organic complexants. New chemical processes are needed to separate chromium and other metals from tank wastes. Ideally they should not utilize additional reagents which would increase waste volume or require subsequent removal. The goal of this project is to apply hydrothermal processing for enhanced chromium separation from HLW sludges. Initially, the authors seek to develop a fundamental understanding of chromium speciation, oxidation/reduction and dissolution kinetics, reaction mechanisms, and transport properties under hydrothermal conditions in both simple and complex salt solutions. The authors also wish to evaluate the potential of hydrothermal processing for enhanced separations of technetium and TRU by examining technetium and TRU speciation at hydrothermal conditions optimal for chromium dissolution.'
Date: June 1, 1997
Creator: Buelow, S.
Partner: UNT Libraries Government Documents Department

Investigation of microscopic radiation damage in waste forms using ODNMR and AEM techniques. 1998 annual progress report

Description: 'This project seeks to understand the microscopic effects of radiation damage in nuclear waste forms. The authors approach to this challenge encompasses studies of crystals and glass containing short-lived alpha- and beta-emitting actinides with electron microscopy, laser spectroscopy, and computational modeling and simulation. Much of the initial effort has focused on alpha-decay induced microscopic damage in 17-year old samples of crystalline yttrium and lutetium orthophosphates and thorium dioxide that initially contained {approximately}1% of the alpha-emitting isotope Cm-244 (18.1 y half life) or the beta-emitting isotope Bk-249 (0.88 y half life). Studies will also be conducted on borosilicate glasses that contain Cm-244 or Am-241, respectively. The goal is to gain clear insight into accumulated radiation damage and the influence of aging on such damage, which are critical factors in the long-term performance of high-level nuclear waste forms. Amorphization previously has been thought to be the most important effect of radiation damage in crystalline and ceramic materials. The studies show that for alpha-emitting actinide ions in certain crystalline phosphates, amorphization is not a significant effect of radiation damage. Instead, formation of microscopic cavities (bubbles) is an important consequence of alpha-decay events. This amorphization-resistant property makes orthophosphates a very attractive high level nuclear waste form. However, aggregation and mobilization of cavities (bubbles) might increase the leach rate of radionuclides and influence the long-term stability of the waste forms. Further research is needed before the authors can draw a final conclusion on the long-term effects of radiation damage in high level waste forms.'
Date: June 1, 1998
Creator: Liu, G.
Partner: UNT Libraries Government Documents Department

Radiation effects on materials in the near-field of a nuclear waste repository. 1997 annual progress report

Description: 'Sheet silicates (e.g. micas and clays) are important constituents of a wide variety of geological formations such as granite, basalt, and sandstone. Sheet silicates, particularly clays such as bentonite are common materials in near-field engineered barriers in high-level nuclear waste (HLW) repositories. This is because migration of radionuclides from an underground HLW repository to the geosphere may be significantly reduced by sorption of radionuclides (e.g., Pu, U and Np) onto sheet silicates (e.g., clays and micas) that line the fractures and pores of the rocks along groundwater flowpaths. In addition to surface sorption, it has been suggested that some sheet silicates may also be able to incorporate many radionuclides, such as Cs and Sr, in the inter-layer sites of the sheet structure. However, theability of the sheet silicates to incorporate radionuclides and retard release and migration of radionuclides may be significantly affected by the near-field radiation due to the decay of fission products and actinides. for example, the unique properties of the sheet structures will be lost completely if the structure becomes amorphous due to irradiation effects. Thus, the study of irradiation effects on sheet-structures, such as structural damage and modification of chemical properties, are critical to the performance assessment of long-term repository behavior.'
Date: November 25, 1997
Creator: Wang, L.M. & Ewing, R.C.
Partner: UNT Libraries Government Documents Department

Interfacial radiolysis effects in tank waste speciation. 1997 annual progress report

Description: 'The purpose of this program is to deliver pertinent, fundamental information that can be used to make technically defensible decisions on safety issues and processing strategies associated with mixed chemical and radioactive waste cleanup. In particular, an understanding of radiolysis in mixed-phase systems typical of U. Department of Energy (DOE) heterogeneous, radioactive/chemical wastes will be established. This is an important scientific concern with respect to understanding tank waste chemistry issues; it has received relatively little attention. The importance of understanding solid-state radiolysis, secondary electron interactions, charge-transfer dynamics, and the general effect of heterogeneous solids (interface and particulate surface chemistry) on tank waste radiation processes will be demonstrated. In particular, the author will investigate (i) the role of solid-state and interfacial radiolysis in the generation of gases, (ii) the mechanisms of organic compound degradation, (iii) scientific issues underlying safe interim storage, and (iv) the effects of colloid surface-chemical properties on waste chemistry. Controlled radiolysis studies of NaNO{sub 3} solids and SiO{sub 2} particles were carried out using pulsed, low- (5--150 eV) and high- (3 MeV) energy electron-beams at Pacific Northwest National Laboratory (PNNL) and at Argonne National Laboratory (ANL), respectively. The pulsed, low-energy electron beams probe the inelastic scattering and secondary cascading effects produced by high-energy beta and gamma particles. Pulsed radiolysis allows time-resolved measurements of the high-energy processes induced by these particles. Using low-energy (10--75 eV) electron-beam irradiation of nominally dry NaNO{sub 3} solution-grown and melt-grown single crystals, they observed H{sup +}, Na{sup +}, O{sup +}, NO{sup +}, NO, NO{sub 2}, O{sub 2}, and O({sup 3}P) desorption signals. The threshold measurements and yields indicate that the degradation proceeds mainly via destruction of the nitrate moiety. The H{sup +} and Na{sup +} yields are primarily related to the presence of water and Na metal, Na hydrides and oxides, or other defect ...
Date: June 1, 1997
Creator: Orlando, T.M.
Partner: UNT Libraries Government Documents Department

The NOx system in nuclear waste. 1998 annual progress report

Description: 'The objective of this project is to assist EM sites in the resolution of outstanding safety issues involved in the temporary storage of high-level waste (HLW) in large tanks. To achieve this objective, mechanisms of the radiolytic and radiolytically induced processes that occur in the waste are quantitatively studied. The information is incorporated into a computer modeling of the tanks chemistry under various scenarios and the predicted results are rapidly conveyed to the site operators. This report summarizes the technical achievements of a 3-year project that is now in its 2nd year of operation. The project is a collaborative effort between the ANL and PNNL and is strongly coupled to another EMSP project (``Interfacial Radiolysis Effects in Tank Waste Speciation'''' PI: T. Orlando, PNNL) and to the safety programs at the Hanford site (``Organic Tanks Safety Program: Waste Aging Studies'''', PI D. Camaioni, PNNL). Information from the project is also shared directly with Westinghouse Savannah River personnel. In general, the basic studies are performed at ANL and PNNL and the information is continuously shared with Tanks Safety Programs. To further facilitate the exchange of information and the immediate incorporation of results into operations, the authors conducted at least twice a year coordination meetings at the various laboratories where the site operators (e.g. from DE and SH, Numatec, WSRC, etc.) participate, both to present their needs and to obtain updated information.'
Date: June 1, 1998
Creator: Meisel, D. & Camaioni, D.
Partner: UNT Libraries Government Documents Department

Investigation of microscopic radiation damage in waste forms using ODNMR and AEM techniques. 1997 annual progress report

Description: 'This project seeks to understand the microscopic effects of radiation damage in nuclear waste forms. The authors approach to this challenge encompasses studies in electron microscopy, laser spectroscopy, and computational modeling and simulation. During this first year of the project, efforts have focused on a-decay induced microscopic damage in crystalline orthophosphates (YPO{sub 4} and LuPO{sub 4}) that contain the short-lived a-emitting isotope {sup 244}Cm (t{sub 1/2} = 18.1 y). The samples that they studied were synthesized in 1980 and the initial {sup 244}Cm concentration was {approximately}1%. Studying these materials is of importance to nuclear waste management because of the opportunity to gain insight into accumulated radiation damage and the influence of aging on such damage. These factors are critical to the long-term performance of actual waste forms [1]. Lanthanide orthophosphates, including LuPO{sub 4} and YPO{sub 4}, have been suggested as waste forms for high level nuclear waste [2] and potential hosts for excess weapons plutonium [3,4]. The work is providing insight into the characteristics of these previously known radiation-resistant materials. They have observed loss of crystallinity (partial amorphization) as a direct consequence of prolonged exposure to intense alpha radiolysis in these materials. More importantly, the observation of microscopic cavities in these aged materials provides evidence of significant chemical decomposition that may be difficult to detect in the earlier stages of radiation damage. The preliminary results show that, in characterizing crystalline compounds as high level nuclear waste forms, chemical decomposition effects may be more important than lattice amorphization which has been the focus of many previous studies. More extensive studies, including in-situ analysis of the dynamics of thermal annealing of self-radiation induced amorphization and cavity formation, will be conducted on these aged {sup 244}Cm:LuPO{sub 4} and {sup 244}Cm:YPO{sub 4} samples, along with other related compounds and glasses, in next two years ...
Date: September 1, 1997
Creator: Liu, G.
Partner: UNT Libraries Government Documents Department

How to Shape a Successful Repository Program: Staged Development of Geologic Repositories for High-Level Waste

Description: Programs to manage and ultimately dispose of high-level radioactive wastes are unique from scientific and technological as well as socio-political aspects. From a scientific and technological perspective, high-level radioactive wastes remain potentially hazardous for geological time periods--many millennia--and scientific and technological programs must be put in place that result in a system that provides high confidence that the wastes will be isolated from the accessible environment for these many thousands of years. Of course, ''proof'' in the classical sense is not possible at the outset, since the performance of the system can only be known with assurance, if ever, after the waste has been emplaced for those geological time periods. Adding to this challenge, many uncertainties exist in both the natural and engineered systems that are intended to isolate the wastes, and some of the uncertainties will remain regardless of the time and expense in attempting to characterize the system and assess its performance.
Date: October 3, 2004
Creator: Isaacs, T.
Partner: UNT Libraries Government Documents Department

Fundamental chemistry, characterization, and separation of technetium complexes in Hanford waste. 1998 annual progress report

Description: 'The ultimate goal of this proposal is to separate technetium from Hanford tank waste. The recent work has shown that a large portion of the technetium is not pertechnetate (TcO{sub 4}{sup -}) and is not easily oxidized. This has serious repercussions for technetium partitioning schemes because they are designed to separate this chemical form. Rational attempts to oxidize these species to TcO{sub 4}{sup -} for processing or to separate the non-pertechnetate species themselves would be facilitated by knowing the identity of these complexes and understanding their fundamental chemistry. Tank characterization work has not yet identified any of the non-pertechnetate species. However, based on the types of ligands available and the redox conditions in the tank, a reasonable speculation can be made about the types of species that may be present. Thus, this proposal will synthesize and characterize the relevant model complexes of Tc(III), Tc(IV), and Tc(V) that may have formed under tank waste conditions. Once synthesized, these complexes will be used as standards for developing and characterizing the non-pertechnetate species in actual waste using instrumental techniques such as capillary electrophoresis electrospray mass spectrometry (CE-MS), x-ray absorbance spectroscopy (EXAFS and XANES), and multi-nuclear NMR (including {sup 99}Tc NMR). The authors study the redox chemistry of the technetium complexes so that more efficient and selective oxidative methods can be used to bring these species to TcO{sub 4}{sup -} for processing purposes. They will also study their ligand substitution chemistry which could be used to develop separation methods for non-pertechnetate species. Understanding the fundamental chemistry of these technetium complexes will enable technetium to be efficiently removed from the Hanford tank waste and help DOE to fulfill its remediation mission. This report summarizes the first 8 months of a 3-year project.'
Date: June 1, 1998
Creator: Schroeder, N.C.; Blanchard, D.L. Jr. & Ashley, K.R.
Partner: UNT Libraries Government Documents Department

Kinetics and mechanisms of metal retention/release in geochemical processes in soil. 1997 annual progress report

Description: 'Remediation of soils polluted with heavy metals is a major challenge facing the nation. This is especially so at many DOE facilities and other superfund sites. In many cases, speciation of the metals is inaccurate and difficult and the mechanisms by which the metals are retained/released in soils over long times are poorly understood. Consequently, the long-term fate of metals in soils cannot be precisely predicted and often, the remediation recommendations and techniques that are employed to clean up soils may be ineffective or unnecessary. Accordingly, the authors are proposing work to generate basic knowledge on the kinetics and mechanism(s) of heavy metal retention/release by soil mineral colloids as affected by inorganic anion. The nature of the interaction of Cd(II), Co(II), Cr(VI), Cu(II), Ni(II) and Pb(II) with pure soil minerals and extracted soil clays will be investigated. The colloids will be characterized in terms of surface area, surface charge and surface site density. They will be used to study the effect(s) of pH, phosphate rate, and temperature on metals retention/release. The experiments will involve using various kinetic and isothermic sorption equations as models to describe the data thus acquired. The spectroscopic methods will involve using extended x-ray absorption fine structure spectroscopy (EXAFS) and Fourier Transform Infrared Spectroscopy (FTIR). The data generated from the proposed study will assist in designing better remediation strategies to effectively clean up toxic heavy metal contaminated soils at DOE facilities and other superfund sites.'
Date: May 1, 1997
Creator: Taylor, R.W.
Partner: UNT Libraries Government Documents Department

Joint inversion of geophysical data for site characterization and restoration monitoring. 1998 annual progress report

Description: 'The purpose of this project is to develop a computer code for joint inversion of seismic and electrical data, to improve underground imaging for site characterization and remediation monitoring. The computer code developed in this project will invert geophysical data to obtain direct estimates of porosity and saturation underground, rather than inverting for seismic velocity and electrical resistivity or other geophysical properties. This is intended to be a significant improvement in the state-of-the-art of underground imaging, since interpretation of data collected at a contaminated site would become much less subjective. Potential users include DOE scientists and engineers responsible for characterizing contaminated sites and monitoring remediation of contaminated sites. In this three-year project, the authors use a multi-phase approach consisting of theoretical and numerical code development, laboratory investigations, testing on available laboratory and borehole geophysics data sets, and a controlled field experiment, to develop practical tools for joint electrical and seismic data interpretation. This report summarizes work after about 1.7 years of a 3-year project. Progress on laboratory measurements is described first, followed by progress on developing algorithms for the inversion code to relate geophysical data to porosity and saturation.'
Date: June 1, 1998
Creator: Berge, P. A.; Roberts, J. J.; Berryman, J. G. & Wildenschild, D.
Partner: UNT Libraries Government Documents Department

Potential-modulated intercalation of alkali cations into metal hexacyanoferrate coated electrodes. 1998 annual progress report

Description: 'This program is studying potential-driven cation intercalation and deintercalation in metal hexacyanoferrate compounds, with the eventual goal of creating materials with high selectivity for cesium separations and long cycle lifetimes. The separation of radiocesium from other benign cations has important implications for the cost of processing a variety of cesium contaminated DOE wasteforms. This report summarizes results after nine months of work. Much of the initial efforts have been directed towards quantitatively characterizing the selectivity of nickel hexacyanoferrate derivatized electrodes for intercalating cesium preferentially over other alkali metal cations. Using energy dispersive xray spectroscopy (ex-situ, but non-destructive) and ICP analysis (ex-situ and destructive), the authors have demonstrated that the nickel hexacyanoferrate lattice has a strong preference for intercalated cesium over sodium. For example, when ions are reversibly loaded into a nickel hexacyanoferrate thin film from a solution containing 0.9999 M Na{sup +} and 0.0001 M Cs{sup +}, the film intercalates 40% as much Cs{sup +} as when loaded from pure 1 M Cs{sup +} containing electrolyte (all electrolytes use nitrates as the common anion). The authors have also shown that, contrary to the common assumptions found in the literature, a significant fraction of the thin film is not active initially. A new near infrared laser has been purchased and is being added to the Raman spectroscopy facilities to allow in-situ studies of the intercalation processes.'
Date: June 1, 1998
Creator: Schwartz, D.T.
Partner: UNT Libraries Government Documents Department