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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Siting considerations for a deep borehole disposal facility - 15403

This paper describes considerations for siting and designing a facility for deep borehole disposal of spent nuclear fuel (SNF) and/or high-level radioactive waste (HLW). Technical considerations include geological, hydrogeochemical, and geophysical characteristics that are related to the suitability of the site for deep drilling and borehole construction, waste emplacement activities, waste isolation (seals and surrounding geology), and long-term safety of the deep borehole disposal system. Logistical factors to be considered include: local or regional availability of drilling contractors (equipment, services, and materials) capable of drilling a large-diameter hole to approximately 5,000 m depth; construction of surface facilities and waste handling and emplacement equipment; legal and regulatory requirements associated with drilling, operation, and post-closure; and access to transportation systems. Social and political considerations include the distance from population centers and the support or opposition of local and state entities and other stakeholders to the facility and its operations. These technical, logistical, and socio-political factors are examined in the context of a consent-based siting process for a deep disposal borehole, which would be the first phase in developing an operating facility. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Planning for Future Implementation of Section 180(c) of the Nuclear Waste Policy Act: DOE's Policy Implementation Exercise - 16612

The Department of Energy (DOE) Office of Nuclear Energy, Nuclear Fuels Storage and Transportation Planning Project (NFST) is currently conducting a 2-year Section 180(c) Proposed Policy Implementation Exercise (the Exercise) with eight states and one Native American Tribe. Under Section 180(c) of the Nuclear Waste Policy Act of 1982 (NWPA), as amended, the DOE is responsible for providing technical and financial assistance to states and Tribes through whose jurisdictions the Secretary of Energy plans to transport spent nuclear fuel (SNF) or high-level radioactive waste to a NWPA-authorized facility for training of local public safety officials. In the 2000's, DOE staff worked closely with state and tribal representatives to develop a revised proposed policy to implement Section 180(c), including grants for assessment and planning activities, as well as training for public safety officials. This revised proposed policy was published in a Federal Register Notice in 2008 (2008 FRN) (73 Federal Register 64933, Oct. 31, 2008). The purpose of the current Exercise is to evaluate the efficacy of DOE's 2008 revised proposed policy for implementing Section 180(c), and identify and resolve outstanding issues. This paper describes how the Exercise was collaboratively designed between DOE and state and tribal stakeholders; how it is being conducted; the interim lessons learned from the first year of the Exercise; and how it may inform and improve future consultations between DOE and state, tribal, and local public safety officials. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Biomass and salt-dependent effects of Bacillus spores on radionuclide migration from the Waste Isolation Pilot Plant

Spores of a Bacillus sp., isolated from radioactive waste, were tested for their ability to influence the fate and transport of neodymium (Nd3+) under high salt conditions expected at the Waste Isolation Pilot Plant (WIPP) nuclear waste repository. Spores were suspended in neodymium-spiked saline solutions up to 4 M NaCl, and concentrations of Nd and the complexing agent dipicolinic acid (DPA), a component of spores, were monitored along with optical densities and spore numbers. Overall, results support neodymium bioassociation that is dependent upon biomass, with more apparent adsorption occurring at higher spore concentrations. However, probable spore lysis in 2 and 4 M NaCl solutions and possible germination at 0.15 M NaCl appear to drive the release of DPA and subsequent return of Nd to solution. The implications of this work for the WIPP will depend on actual biomass levels and the ionic strength of the repository brines.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Remaking the US nuclear waste program: a window of opportunity for change? - 15352

John Kingdon's 1984 policy analytic approach is utilized to examine nuclear waste policy in the United States over the last three decades. Kingdon's premise concerning the merging of three process streams - the problem stream, the political stream, and the policy stream - to create a policy window, took place when major changes in U.S. management of high-level radioactive waste and spent nuclear fuel occurred in 1982 and 1987. These three streams have once again converged, with events beginning in 2006, creating an opportunity to move beyond the current Yucca Mountain stalemate by adopting the recommendations of the Blue Ribbon Commission (BRC) on America's Nuclear Future in 2012. Legislation introduced in the U.S. Senate in 2013 to redirect the waste program along the lines suggested by the BRC has been reintroduced as the Nuclear Waste Administration Act of 2015, S. 854. The authors examine key provisions of S. 854 and suggest amendments requiring written consent agreements with governors of all potential host states, including Nevada; the same requirements for commingled and separate defense waste facilities; and additional measures to enhance nuclear waste transportation safety, security, and public acceptance. The Nuclear Waste Informed Consent Act (S. 691, 2015; H.R. 1364, 2015) is also examined. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Reduction of the Waste Occupied Area by Nuclide Separation and Horizontal Emplacement of the Waste Packages - 20422

Two of the key objectives for realizing the advanced nuclear fuel cycle are to reduce the volume of high-level radioactive waste and to reduce the foot-print of the geological repository. To achieve these objectives, research and development on nuclide separation technologies is a prerequisite. In this context, it is necessary to consider the vitrification conditions and the design of the geological repository where separation technologies would be implemented to achieve effective reductions in the volume of vitrified waste and the foot-print of the geological repository. In this study, the effects of the vitrification conditions on the number of vitrified waste units and the disposal area were evaluated, based on the assumption that separation of Cs and Sr from the spent nuclear fuel had been performed. In addition, with reference to the design of the geological repository, the impact on the foot-print of the repository for different emplacement methods of the waste packages was examined. As a result, it was clarified that the waste-occupied area could be reduced by horizontal emplacement of the vitrified waste with low heat generation. In addition, it was demonstrated that a low waste-loaded vitrified waste contributed to a reduction in the foot-print of the geological repository in the case of horizontal emplacement, although the number of vitrified waste units increased. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Cleaning Up Nuclear Wastes

Environmental management is a key DOE mission, in large part because decades of nuclear weapons production and nuclear energy research have left behind huge quantities of radioactive waste. Most of the radioactivity in the waste, however, comes from the element cesium, which is just a tiny fraction of the total waste. An alert research chemist at Oak Ridge National Laboratory, Bruce Moyer, recognized that if cesium could be removed, dealing with the wastes would be much easier and safer. Moyer also was aware of a potential solution—fundamental research into organic molecules that can recognize and capture metal atoms like cesium, some of it supported by the Basic Energy Sciences (BES) office of DOE. With BES support, he put together a team that, over a decade, showed the potential of this approach. Subsequent support by DOE’s Environmental Management Office allowed the team to work out the practical details.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Impact of a Biological Chelator, Lanmodulin, on Minor Actinide Aqueous Speciation and Transport in the Environment

Minor actinides are major contributors to the long-term radiotoxicity of nuclear fuels and other radioactive wastes. Here in this context, understanding their interactions with natural chelators and minerals is key to evaluating their transport behavior in the environment. The lanmodulin family of metalloproteins is produced by ubiquitous bacteria and Methylorubrum extorquens lanmodulin (LanM) was recently identified as one of nature’s most selective chelators for trivalent f-elements. Herein, we investigated the behavior of neptunium, americium, and curium in the presence of LanM, carbonate ions, and common minerals (calcite, montmorillonite, quartz, and kaolinite). We show that LanM’s aqueous complexes with Am(III) and Cm(III) remain stable in carbonate-bicarbonate solutions. Furthermore, the sorption of Am(III) to these minerals is strongly impacted by LanM, while Np(V) sorption is not. With calcite, even a submicromolar concentration of LanM leads to a significant reduction in the Am(III) distribution coefficient (K d , from >10 4 to ~10 2 mL/g at pH 8.5), rendering it even more mobile than Np(V). Thus, LanM-type chelators can potentially increase the mobility of trivalent actinides and lanthanide fission products under environmentally relevant conditions. Monitoring biological chelators, including metalloproteins, and their biogenerators should therefore be considered during the evaluation of radioactive waste repository sites and the risk assessment of contaminated sites.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2016

De-Inventory Plan for Transuranic Waste Stored at Area G

This report describes the strategy and detailed work plan developed by Los Alamos National Laboratory (LANL) to disposition transuranic (TRU) waste stored at its Area G radioactive waste storage site. The focus at this time is on disposition of 3,706 m 3 of TRU waste stored above grade by June 30, 2014, which is one of the commitments within the Framework Agreement: Realignment of Environmental Priorities between the Department of Energy (DOE) National Nuclear Security Administration (NNSA) and the State of New Mexico Environment Department (NMED), Reference 1. A detailed project management schedule has been developed to manage this work and better ensure that all required activities are aligned and integrated. The schedule was developed in conjunction with personnel from the NNSA Los Alamos Site Office (LASO), the DOE Carlsbad Field Office (CBFO), the Central Characterization Project (CCP), and Los Alamos National Security, LLC (LANS). A detailed project management schedule for the remainder of the above grade inventory and the below grade inventory will be developed and incorporated into the De-Inventory Plan by December 31, 2012. This schedule will also include all newly-generated TRU waste received at Area G in FYs 2012 and 2013, which must be removed by no later than December 31, 2014, under the Framework Agreement. The TRU waste stored above grade at Area G is considered to be one of the highest nuclear safety risks at LANL, and the Defense Nuclear Facility Safety Board has expressed concern for the radioactive material at risk (MAR) contained within the above grade TRU waste inventory and has formally requested that DOE reduce the MAR. A large wildfire called the Las Conchas Fire burned extensive areas west of LANL in late June and July 2011. Although there was minimal to no impact by the fire to LANL, the fire heightened public concern and news media attention on TRU waste storage at Area G. After the fire, New Mexico Governor Susana Martinez also requested that LANL accelerate disposition of TRU waste stored above grade at Area G. The 3,706 m 3 volume of TRU waste stored above grade consists of 4,495 containers that include all above grade non-cemented waste as well as above grade cemented waste that was ready for characterization on October 1, 2011. This volume includes all newly-generated TRU waste currently stored at Area G as of October 1, 2011. This volume does not include the Bolas Grandes spheres, mixed low level waste (MLLW) containers, empty containers, cemented waste that requires remediation, projected newly generated TRU waste from FY 2012 and later, or TRU waste stored below grade. The 3,706 m 3 volume represents about 86 per cent of the total volume of TRU waste stored above grade on October 1, 2011. The De-Inventory Plan supports the DOE Office of Environmental Management (EM) goal to disposition 90% of the Legacy TRU waste within the DOE complex by the end of 2015 as stated in its Roadmap for EM’s Journey to Excellence (Reference 2). The plan also addresses precursor actions for disposition of TRU waste that are necessary for compliance with the Compliance Order on Consent issued by the NMED in 2005 (Reference 3).

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Panel Session 120B: DOE Portsmouth Paducah Project Office (PPPO) Update

This panel focused on the Portsmouth/Paducah Project Office (PPPO) of the US DOE Office of Environmental Management, Lexington, Kentucky, the US DOE Featured Site for Thursday. It showcased recent progress, challenges and planned efforts in radioactive waste management, waste disposition, environmental remediation and D and D at the Portsmouth (Ohio) and Paducah (KY) Gaseous Diffusion Plant Sites, as well as the Depleted Uranium Hexafluoride (DUF6) Conversion Project with facilities at both sites Presentations proposed include: 1 - Portsmouth/Paducah Project Office (PPPO) (Joel Bradburne, US DOE Portsmouth/Paducah Project Office (USA)); 2 - Portsmouth (Jeff Bettinger, US DOE Portsmouth/Paducah Project Office (USA)); 3 - Paducah (Jennifer Woodard, US DOE Portsmouth/Paducah Project Office (USA)); 4 - Depleted Uranium Hexafluoride Conversion Project (Reinhard Knerr, US DOE Portsmouth/Paducah Project Office (USA)); 5 - Portsmouth Deactivation and Demolition Project (Bob Smith, Fluor-BWXT Portsmouth (USA)); 6 - Paducah Deactivation and Remediation Project (Jeff Bradford, Four Rivers Nuclear Partnership - FRNP (USA)); 7 - Seven Lines-One Project (Zack Smith, SNC Lavalin (USA))

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Section 180(c) Policy Implementation Exercise: Multiple Views - 17383

The Department of Energy (DOE) Office of Nuclear Energy's Office of Integrated Waste Management (formerly the Nuclear Fuels Storage and Transportation Planning Project) recently completed a two-year Section 180(c) Proposed Policy Implementation Exercise (the Exercise) with volunteers from eight states and one Native American Tribe. Under Section 180(c) of the Nuclear Waste Policy Act of 1982, as amended (NWPA), DOE is responsible for providing technical and financial assistance to states and Tribes for training of local public safety officials through whose jurisdictions the Secretary of Energy plans to transport spent nuclear fuel (SNF) or high-level radioactive waste to a NWPA-authorized facility. In the 2000's, DOE staff worked closely with state and tribal representatives to develop a revised proposed policy to implement Section 180(c), including grants for assessment and planning activities, as well as grants for training public safety officials. This revised proposed policy was published in a Federal Register Notice in 2008 (2008 FRN) (73 Federal Register 64933, Oct. 31, 2008). The purpose of the Exercise was to evaluate the efficacy of DOE's 2008 revised proposed policy for implementing Section 180(c), and identify outstanding issues to be resolved. DOE presented an interim update on the Exercise at the 2016 Waste Management Symposium and the Exercise concluded in June 2016. This paper describes the remaining activities of the Exercise that occurred since the 2016 Waste Management Symposium, and presents the perspectives of one state and one Tribal participant in the Exercise as well as DOE's perspective. The paper concludes with a discussion of the lessons learned from the Exercise, what steps are next, and how the Exercise may inform and improve future consultations between DOE and state, tribal, and local public safety officials. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Sorption of radionuclides by cement-based barrier materials

This paper investigates the sorption of radionuclide ions, {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+}, by cement-based barrier materials for radioactive waste disposal. A mortar with ternary binder is prepared and powder samples are ground from the hardened material following a predetermined granulometry. After pre-equilibrium with an artificial pore solution, the sorption behaviors of powder samples are investigated through single sorption and blended sorption. The results show that: (1) no systematic difference is observed for single and blended sorptions thus the interaction between {sup 137}Cs{sup +} and {sup 90}Sr{sup 2+} sorptions must be weak; (2) the sorption kinetics is rapid and all characteristic times are less than 1d; (3) the sorption capacity is enhanced by C–A–S–H hydrates and the measured K{sub d} values can be predicted from C–S–H sorption data with Ca/Si ratio equal to Ca/(Si + Al) ratio.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

The controlling role of atmosphere in dawsonite versus gibbsite precipitation from tetrahedral aluminate species

In highly alkaline solution, aluminum speciates as the tetrahedrally coordinated aluminate monomer, Al(OH)4- and/or dimer Al2O(OH)62-, yet precipitates as octahedrally coordinated gibbsite (Al(OH)3). This tetrahedral to octahedral transformation governs Al precipitation, which is crucial to worldwide Al production, and to the processing of caustic high-level radioactive wastes. Despite its significance, the transformation pathway remains unknown. Here we explore the roles of atmospheric water and carbon dioxide in mediating the transformation of the tetrahedrally coordinated potassium aluminate dimer salt (K2Al2O(OH)6) to gibbsite versus potassium dawsonite (KAl(CO3)(OH)2). A combination of in-situ attenuated total reflection infrared spectroscopy, ex-situ micro X-ray diffraction, and multivariate curve resolution-alternating least squares chemometrics analysis reveals that humidity plays a key role in the transformation by limiting the amount of alkalinity neutralization by dissolved CO2. Lower humidity favors higher alkalinity and incorporation of carbonate species in the final Al product to form KAl(CO3)(OH)2. Higher humidity enables more acid generation that destabilizes dawsonite and favors gibbsite as the solubility limiting phase. Because the transformation was restricted to occur in thin water films, the results suggest that transition from tetra- to octahedrally coordinated Al does not have to occur in bulk solution, as has often been hypothesized, but may instead appear on the source mineral surface.

Dembowski, Mateusz↗
DOE OSTI2016

Radiochemical Method for Characterization of the Filter Cartridges from the IEA-R1 Reactor - 16324

The filter cartridges used in water purification system of the IEA-R1 research reactor become radioactive waste after the end of their useful life. The characterization of this waste is one step in their management, which aims at identifying and quantifying the radionuclides present, including those known as 'difficult to measure' (DTM) radionuclides. Wastes from nuclear reactors contain fission and activation products and transuranic elements, only few of them emitting gamma radiation measurable by simple gamma spectrometry methods. In routine waste management activities, the concentrations of the DTM can only be estimated by indirect methods such as scaling factors. The method of the scaling factors uses empirically determined proportions between the concentrations of DTM radionuclides and that of easily measurable gamma emitters called key nuclides (KN), to calculate DTM concentrations. Determining the scaling factors for the filter cartridges is a hard task when the number of samples is large, not only because the preparation of samples is difficult but also because the number of radionuclides to analyze is large. If it can be demonstrated that DTM and KN are both distributed evenly in the filters, less samples from each filter are necessary, reducing lab work. The aim of this paper is to present the results of the assessment of homogeneity along the filter cartridges by gamma spectrometry of chemically reduced samples. Five thin slices of five filters were burnt and the ashes quantitatively dissolved and the activity concentration of the solutions determined by gamma spectrometry. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Development of Electrochemical Detectors for Elemental Characterization of Actinides - 20563

The characterization of the actinides contained in radioactive waste involves complex and expensive separation processes. Electrochemical methods allow identifying and quantifying quickly and accurately the elementary concentration of actinides such as Th, U, Pu, Am, and Cm in liquid waste. The objective of this research proposal is to build a low-cost portable miniaturized electrochemical detector, which can be an alternative for an initial characterization of actinides in liquid waste. Therefore, this work proposes the use of an electrochemical graphite detector modified with phthalocyanine, to detect and quantify actinides in aqueous media. The electrochemical response of the modified graphite electrodes was performed by cyclic voltammetry, and so the detection and quantification limits for U and Th were determined. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Presence of aromatic-rich organic matter and its characterization in grout materials: Implications for radionuclide immobilization

Grout materials are commonly used to immobilize low-level radioactive waste. Organic moieties can be unintentionally present in common ingredients used to make these grout waste forms, which may result in the formation of organo-radionuclide species. These species can positively or negatively affect the immobilization efficiency. However, the presence of organic carbon compounds is rarely considered in models or characterized chemically. Here, we quantify the organic pool of grout formulations with and without slag, as well as the individual dry ingredients used to make the grout samples (ordinary Portland cement (OPC), slag and fly ash), including total organic carbon (TOC) and black carbon, followed by aromaticity evaluation and molecular characterization via Electro Spray Ionization Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry (ESI-FTICRMS). All dry grout ingredients contained significant amounts of organic carbon, ranging from 550 mg/kg to 6250 mg/kg for the TOC pool, with an averaged abundance of 2933 ± 2537 mg/kg, of which 60 ± 29% was composed of black carbon. The significant abundance of a black carbon pool implies the presence of the aromatic-like compounds, which was further identified by both phosphate buffer-assisted aromaticity evaluation (e.g., >1000 mg-C/kg as aromatic-like carbon in the OPC) and dichloromethane (DCM) extraction with ESIFTICRMS analysis. Besides aromatic-like compounds, other organic moieties were also detected in the OPC, such as carboxyl-containing aliphatic molecules. While the organic compound only consists of minor fractions of the grout materials investigated, our observations of the presence of various radionuclide-binding organic moieties suggests the potential formation of organo-radionuclides, such as radioiodine, which might be present at lower molar concentrations than TOC. Here, evaluating the role of organic carbon complexation in controlling the disposed radionuclides, especially for those radionuclides with strong association with organic carbon, has important implications for the long-term immobilization of radioactive waste in grout systems.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Phenomenological Model of Nonlinear Dynamics and Deterministic Chaotic Gas Migration in Bentonite: Experimental Evidence and Diagnostic Parameters

Understanding gas migration in compacted clay materials, e.g., bentonite and claystone, is important for the design and performance assessment of an engineered barrier system of a radioactive waste repository system, as well as many practical applications. Existing field and laboratory data on gas migration processes in low-permeability clay materials demonstrate the complexity of flow and transport processes, including various types of instabilities, caused by nonlinear dynamics of coupled processes of liquid–gas exchange, dilation, fracturing, fracture healing, etc., which cannot be described by classical models of fluid dynamics in porous media. We here show that the complexity of gas migration processes can be explained using a phenomenological concept of nonlinear dynamics and deterministic chaos theory. To do so, we analyzed gas pressure and gas influx (i.e., input) and outflux (i.e., output), recorded during the gas injection experiment in the compact Mx80-D bentonite sample, and calculated a set of the diagnostic parameters of nonlinear dynamics and chaos, such a global embedding dimension, a correlation dimension, an information dimension, and a spectrum of Lyapunov exponents, as well as plotted 2D and 3D pseudo-phase-space strange attractors, based on the univariate influx and outflux time series data. These results indicate the presence of phenomena of low-dimensional deterministic chaotic behavior of gas migration in bentonite. In particular, during the onset of gas influx in the bentonite core, before the breakthrough, the development of gas flow pathways is characterized by the process of chaotic gas diffusion. After the breakthrough, with inlet-to-outlet movement of gas, the prevailing process is chaotic advection. During the final phase of the experiment, with no influx to the sample, the relaxation pattern of gas outflux is resumed back to a process of chaotic diffusion. The types of data analysis and a proposed phenomenological model can be used to establish the basic principles of experimental data-gathering, modeling predictions, and a research design.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Ion–ion interactions enhance aluminum solubility in alkaline suspensions of nano-gibbsite (α-Al(OH) 3 ) with sodium nitrite/nitrate

Despite widespread industrial importance, predicting metal solubilities in highly concentrated, multicomponent aqueous solutions is difficult due to poorly understood ion–ion and ion–solvent interactions. Aluminum hydroxide solid phase solubility in concentrated sodium hydroxide (NaOH) solutions is one such case, with major implications for ore refining, as well as processing of radioactive waste stored at U.S. Department of Energy legacy sites, such as the Hanford Site, Washington State. The solubility of gibbsite (α-Al(OH) 3 ) is often not well predicted because other ions affect the activity of hydroxide (OH – ) and aluminate (Al(OH) 4 – ) anions. In the study reported herein, we systematically examined the influence of key anions, nitrite (NO 2 – ) and nitrate (NO 3 – ), as sodium salts on the solubility of α-Al(OH) 3 in NaOH solutions taking care to establish equilibrium from both under- and oversaturation. Rapid equilibration was enabled by use of a highly pure and crystalline synthetic nano-gibbsite of well-defined particle size and shape. Measured dissolved aluminum concentrations were compared with those predicted by an α-Al(OH) 3 solubility model derived for simple Al(OH) 4 – /OH – systems. Specific anion effects were expressed as an enhancement factor (Al enhc ) conveying the excess of dissolved aluminum. At 45 °C, NaNO 2 and NaNO 3 -containing systems exhibited Al enhc values of 2.70 and 1.88, respectively, indicating significant enhancement. The solutions were examined by Raman and high-field 27 Al NMR spectroscopy, indicating specific interactions including Al(OH) 4 – –Na + contact ion pairing and Al(OH) 4 – –NO 2 – /NO 3 – ion–ion interactions. Dynamic evolution of the α-Al(OH) 3 particles including growth and agglomeration was observed revealing the importance of dissolution/reprecipitation in establishing equilibrium. These studies indicate that incomplete ion hydration, as a result of the low water activity in these concentrated electrolytes, results in: (i) enhanced reactivity of the hydroxide ion with respect to α-Al(OH) 3 ; (ii) increased concentrations of Al(OH) 4 – in solution; and (iii) stronger ion–ion interactions that act to stabilize the supersaturated solutions. This information on the mechanisms by which α-Al(OH) 3 becomes supersaturated is essential for more energy-efficient aluminum processing technologies, including the treatment of millions of gallons of Al(OH) 4 – -rich high-level radioactive waste.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗