124 research outputs found
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DuoliteTM GT-73 Resin Testing in Support of the Salt Disposition Alternatives
This study evaluated DuoliteTM GT-73 performance for removing mercury ions from several high level waste streams under consideration by the Salt Disposition Systems Engineering Team as a technical risk. Experiments conducted over an eight week period address the technical uncertainties for GT-73 performanc
Skylab 4 visual observations project report
The Skylab 4 Visual Observations Project was undertaken to determine the ways in which man can contribute to future earth-orbital observational programs. The premission training consisted of 17 hours of lectures by scientists representing 16 disciplines and provided the crewmen information on observational and photographic procedures and the scientific significance of this information. During the Skylab 4 mission, more than 850 observations and 2000 photographs with the 70-millimeter Hasselblad and 35-millimeter Nikon cameras were obtained for many investigative areas. Preliminary results of the project indicate that man can obtain new and unique information to support satellite earth-survey programs because of his inherent capability to make selective observations, to integrate the information, and to record the data by describing and photographing the observational sites
The skylab S191 spectrometer experiment: Analysis of data and their applications to the earth sciences
The data in the visible and near-infrared portions of the spectrum as recorded by identical spectrometers on Skylab and on a helicopter are examined to establish the significance of spectral reflectances from the Earth surface as influenced by water vapor, atmospheric gases, and aerosols. Models of radiation transfer show good agreement of theoretical computations and observed measurements
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Decomposition studies of filtered slurries using the enhanced comprehensive catalyst
This study examined decomposition of the soluble phenylborates at elevated temperatures (45 degrees Celsius) to determine the effects of filtering the solid tetraphenylborate, solid sludge and monosodium titanate and spiking additional levels of transition metal catalyst
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Decomposition of triphenylborane with enhanced comprehensive catalyst under aerated and inert conditions
This work investigated the decomposition of triphenylborane in a statistically-designed set of tests to determine the effects of four process variables: temperature, hydroxide concentration, catalyst concentration, and atmosphere. Analysis of these tests provide the following conclusions:(1) The presence of tetraphenylborate solids facilitate a 10X increase in the rate of decomposition of triphenylborane, (2) The presence of oxygen slows the decomposition of triphenylborane, (3) The activation energy of the decomposition reaction in the presence of oxygen (59.88 + 27.73 kJ/mol) is statistically lower than inerted systems (99.11 + 10.14 kJ/mol), (4) Rate constants derived from the nitrogen inerted tests encompass the rate constants from previous tests with slurries. These rate constants agree reasonably with similar values obtained from Tank 48H operations at ambient temperatures, and (5) For test conducted in air, the decomposition reaction rate constant correlated with the catalyst concentration. In tests inerted by nitrogen, the same correlation did not hold
Using Wet Air Oxidation Technology to Destroy Tetraphenylborate
ABSTRACT A bench-scale feasibility study on the use of a Wet Air Oxidation (WAO) process to destroy a slurry laden with tetraphenylborate (TPB) compounds has been undertaken. WAO is an aqueous phase process in which soluble and/or insoluble waste constituents are oxidized using oxygen or oxygen in air at elevated temperatures and pressures ranging from 150 °C and 1 MPa to 320 °C and 22 MPa. The products of the reaction are CO 2 , H 2 O, and low molecular weight oxygenated organics (e.g. acetate, oxalate). Test results indicate WAO is a feasible process for destroying TPB, its primary daughter products [triphenylborane (3PB), diphenylborinic acid (2PB), and phenylboronic acid (1PB)], phenol, and most of the biphenyl byproduct. The required conditions are a temperature of 300 °C, a reaction time of 3 hours, 1:1 feed slurry dilution with 2M NaOH solution, the addition of CuSO 4 .5H 2 O solution (500 mg/L Cu) as catalyst, and the addition of 2000 mL/L of antifoam. However, for the destruction of TPB, its daughter compounds (3PB, 2PB, and 1PB), and phenol without consideration for biphenyl destruction, less severe conditions (280 °C and 1-hour reaction time with similar remaining above conditions) are adequate
CHARACTERIZATION OF URANIUM SOLIDS PRECIPITATED WITH ALUMINOSILICATES
At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility. The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicate (NAS) solids (such as cancrinite and sodalite) that contained close to 10 weight percent of elementally-enriched uranium (U). Prior to extensive cleaning, the evaporator deposits resided on the evaporator walls and other exposed internal surfaces within the evaporator pot. Our goal is to support the basis for the continued safe operation of SRS evaporators and to gain more information that could be used to help mitigate U accumulation during evaporator operation. To learn more about the interaction between U(VI) and NAS in HLW salt solutions, we performed several fundamental studies to examine the mechanisms of U accumulation with NAS in highly caustic solutions. This larger group of studies focused on the following processes: co-precipitation/structural incorporation, sorption, and precipitation (with or without NAS), which will be reviewed in this presentation. We will present and discuss local atomic structural characterization data about U that has been co-precipitated with NAS solids (such as amorphous zeolite precursor material and sodalite or Na 8 (AlSiO 4 ) 6 ·nH 2 O (s) ) using X-ray absorption fine-structure (XAFS) spectroscopic techniques. Our results indicate that U uptake from solution is greater during the precipitation of sodalite and amorphous zeolite precursor material than during the precipitation of zeolite A. The XAFS data indicate that U exists in several forms, such as U(VI) (uranyl-and uranate-type) oxide and oxyhydroxides (such as clarkeite). Crystalline forms of U(VI)-silicate were not resolved from the XAFS spectra but the presence of Si in the outer coordination shell of U indicate that the U is probably associated with amorphous silica. Mass balance determinations for U in these materials indicate that during formation, the structural incorporation of U within these structures is not a likely mechanism for accumulation. However, uptake of U was greatest during the precipitation of amorphous zeolite precursor material. Additionally, removal of U from solution by surface sorption on the NAS solids (a process which could have occurred after these solids were formed) probably had a minor role with respect to U accumulation in the 2H Evaporator. Processes most likely to largely influence on U accumulation are precipitation as U(VI) (as uranyl/uranate) oxide/oxyhydroxides and formation of an amorphous U-silica material. INTRODUCTION Uranium accumulation during the evaporation of HLW is a potential criticality risk if the incoming waste is enriched in 235 U. Little is known about the interactions between U and NAS in caustic, high Na + HLW salt solutions at room and at elevated temperature. To examine these interactions during NAS formation, we conducted studies that focused on potential mechanisms of U accumulation with NAS in the evaporators and in other process areas at the SRS that may concentrate U in the presence of silicates, Al and NAS. It is intended that the information gained from these studies will help support the basis for the continued safe operation of SRS evaporators and that this fundamental information will be used to help mitigate U accumulation during evaporator operation. Potential Routes of U Accumulation with NAS During the evaporation of caustic Na + -rich solutions, several processes could potentially contribute to the accumulation of U-containing solids. Uptake processes by solids can occur by several mechanisms: structural incorporation, ion exchange (electrostatic or outer-sphere) sorption, specific adsorption and surface precipitation/polymerization. WSRC-MS-2003-00898 3 Ion Exchange in a more restrictive sense as used in this study is an electrostatic process involving the replacement of one readily exchangeable hydrated ion by another similarly exchangeable ion Specific Adsorption (often referred to as Chemisorption or Inner Sphere sorption) involves the formation of predominantly covalent bonds with the surface, but the bonds can have some ionic behavior. These adsorbed metals typically have one or more atoms from the participating surface in the second coordination shell In HLW, U may be concentrated by sorption to the surfaces of the NAS, precipitation within NAS structures and precipitation as U phases. Sorption can be divided into two types of molecular scale processes (outer sphere and specific adsorption) that involve the uptake of atoms near or at a participating sorptive surface. An element such as U could co-precipitate with the NAS and related solids. [For zeolites, the term co-precipitation could be further divided to include uptake into zeolite channels and any isomorphic substitution (i.e., of U for Si or Al) in the zeolite structure Uranium may also interact with silica sols, which have no defined crystal structure because of their amorphous nature. At an atom-or molecular-scale basis, this type of interaction with U may be best be described by structural incorporation in Review of U(VI) Chemistry and Uptake Studies with U(VI) and Zeolites In oxidized systems, dissolved U exists as the highly soluble uranyl [U(VI)O 2 2+ ] species with two axial U=O double bonds at ~1.8 Å. This form of U(VI) can exist in U solids. However, U(VI) can also exist in solids as the less common uranate form, which has at least three single U-O bonds and no short axial double bonds. This form of U(VI) is very small in size (~0.72-0.8 Å) relative to the large uranyl ion group (~3.6 Å). 2-or NO 3 -solutions), U(VI) typically has a low affinity for certain solids, like the Fe oxides Use of XAFS Techniques to Characterize Metal Uptake by Surfaces The local environment of metals associated with surfaces can be investigated with analytical techniques such as XAFS spectroscopy. It is an X-ray-based technique that is non-destructive and provides average information on bulk and surface behavior. The XAFS spectroscopic techniques are among the best for providing detailed chemical speciation information in environmental samples-particularly when information from multiple characterization techniques is available. The term XAFS is applicable to both X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopic techniques. XAFS spectra give robust local structural information on coordination number (CN), bonding symmetry, neighbor and near-neighbor atomic distances and bond disorder (as the root mean square deviations of distances about the average values). Additionally, the information gained is atom specific-making it a versatile technique for structural determinations of atom clusters Experimental Objectives The primary objective of this research was to obtain information on speciation of U [added as U(VI)] associated with NAS solids that were synthesized with dissolved U using XAFS. Uranium-XAFS analyses were also conducted on solids that had been washed with solutions of DI water (only) and after washing with DI water and Na 2 CO 3 Washing U-loaded solids with Na 2 CO 3 solutions has been shown to remove sorbed forms of U(VI), in addition to dissolving the readily soluble (i.e., rapidly dissolving) solid phase forms of U(VI) MATERIALS AND EXPERIMENTAL METHODS Sample Preparation The NAS solids (amorphous zeolite, sodalite and zeolite A) were synthesized according to modified methods supplied by A. The difference between the amorphous zeolite and sodalite syntheses was temperature, in that the amorphous zeolite was made at 40 o C and the sodalite was made at 80 o C. Zeolite A was made at 90 o C. After preparation, the solids were washed three times in DI water, filtered with a 0.25 µm nylon filter, and dried in air. The air-dried solids were then washed three times with 0.4 M Na 2 CO 3 , filtered with a 0.25 µm nylon filter, and then air-dried. The air-dried solids were then provided to us for XAFS analyses. Sub-samples of the solids were digested in acid to determine the U concentrations after synthesis (using inductively-coupled argon plasma mass spectrometry) after each of the two washing steps. The results of the sample digests are shown in Additionally, to determine when the U should be added during these NAS syntheses, precipitation timing studies were done with U, Al and caustic salt solutions using the same experimental conditions (such as temperature) as those required for the individual NAS syntheses [ the reference samples as listed in 24]. No Si was added to avoid making NAS for each of these reference U materials. The U added to these solutions underwent precipitation and the unwashed solids were supplied for XAFS analyses. The solids in these "reference" samples may be representative of solids that can form in heated caustic solutions that are low in Si but contain high Al. EXAFS Data Collection and Analyses The XAFS data were collected on beamline X23a2 at the National Synchrotron Light Source (NSLS, Brookhaven National Laboratory, Upton, NY). Uranium-XAFS data were collected at the U L 3 -edge (17,166 eV) on the airdried filtered U-containing NAS solids. The XAFS data were collected in fluorescence mode using an unfocussed X-ray beam and a fixed-exit Si(311) monochromator. Ion chambers were used to collect incident (Io), transmission (It) and reference (Ir) signals. Gas ratios in Io were 100 % Ar. A Lytle detector was used to collect fluorescence X-WM'04 CONFERENCE, FEBRUARY 29-MARCH 4, 2004, TUSCON, AZ. WSRC-MS-2003-00898 6 rays (If). The monochromator energy was maximized using a piezo stack feedback energy stabilization system, with a settling time of 0.3 seconds per change in energy. An X-ray beam size of 2 by 28 mm 2 was used. Energy calibration was done using foils of Pt (L 1 -edge of 13,880 eV), Zr (K-edge, 17,998 eV), and Mo (K-edge, 20,000 eV). In simple terms, chi data (the plot of the wavevector in reciprocal space) show the oscillatory component (with both constructive and destructive interferences) of the atoms in the neighbor environment of the element of interest. The chi data represent part of the photoelectron wave that can be defined by the EXAFS equation Chi of k is the square root of [(2m / • 2 ) * (E -E 0 )]. S 0 2 is the amplitude reduction factor, which is associated with central atom shake-up and shake-off effects. SIGMA 2 or σ 2 is the Debye-Waller Factor or Relative Mean Square Disorder in bond length. "•" is Plank's constant and R pertains to mean atom position or bond distance (radial distance in Å). "m" is the mass of the photoelectron, E 0 is the EXAFS defined edge energy in electron volts or eV (not equal to edge energy as defined by XANES but is equal to the energy of the photoelectron at k = 0. "F of k" is the backscattering amplitude of the atom. N is the coordination number and δ(K) represents the electronic phase shifts due to atomic potentials. The background contribution to the EXAFS spectra was removed using an algorithm (AUTOBK) developed by RESULTS Background on the XAFS Characterization of Behavior of U on Surface
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Enterprise SRS: Leveraging Ongoing Operations To Advance Nuclear Fuel Cycles Research And Development Programs
The Savannah River Site (SRS) is repurposing its vast array of assets to solve future national issues regarding environmental stewardship, national security, and clean energy. The vehicle for this transformation is Enterprise SRS which presents a new, radical view of SRS as a united endeavor for ''all things nuclear'' as opposed to a group of distinct and separate entities with individual missions and organizations. Key among the Enterprise SRS strategic initiatives is the integration of research into facilities in conjunction with on-going missions to provide researchers from other national laboratories, academic institutions, and commercial entities the opportunity to demonstrate their technologies in a relevant environment and scale prior to deployment. To manage that integration of research demonstrations into site facilities, The Department of Energy, Savannah River Operations Office, Savannah River Nuclear Solutions, the Savannah River National Laboratory (SRNL) have established a center for applied nuclear materials processing and engineering research (hereafter referred to as the Center). The key proposition of this initiative is to bridge the gap between promising transformational nuclear fuel cycle processing discoveries and large commercial-scale-technology deployment by leveraging SRS assets as facilities for those critical engineering-scale demonstrations necessary to assure the successful deployment of new technologies. The Center will coordinate the demonstration of R&D technologies and serve as the interface between the engineering-scale demonstration and the R&D programs, essentially providing cradle-to-grave support to the research team during the demonstration. While the initial focus of the Center will be on the effective use of SRS assets for these demonstrations, the Center also will work with research teams to identify opportunities to perform research demonstrations at other facilities. Unique to this approach is the fact that these SRS assets will continue to accomplish DOE's critical nuclear material missions (e.g., processing in H-Canyon and plutonium storage in K-Area). Thus, the demonstration can be accomplished by leveraging the incremental cost of performing demonstrations without needing to cover the full operational cost of the facility. Current Center activities have been focused on integrating advanced safeguards monitoring technologies demonstrations into the SRS H-Canyon and advanced location technologies demonstrations into K-Area Materials Storage. These demonstrations are providing valuable information to researchers and customers as well as providing the Center with an improved protocol for demonstration management that can be exercised across the entire SRS (as well as to offsite venues) so that future demonstrations can be done more efficiently and provide an opportunity to utilize these unique assets for multiple purposes involving national laboratories, academia, and commercial entities. Key among the envisioned future demonstrations is the use of H-Canyon to demonstrate new nuclear materials separations technologies critical for advancing the mission needs DOE-Nuclear Energy (DOE-NE) to advance the research for next generation fuel cycle technologies. The concept is to install processing equipment on frames. The frames are then positioned into an H-Canyon cell and testing in a relevant radiological environment involving prototypic radioactive materials can be performed
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Studies of Potential Inhibitors of Sodium Aluminosilicate Scales in High-Level Waste Evaporation
The Savannah River Site (SRS) has 49 underground storage tanks used to store High Level Waste (HLW). The tank space in these tanks must be managed to support the continued operation of key facilities. The reduction of the tank volumes in these tanks are accomplished through the use of three atmospheric pressure HLW evaporators. For a decade, evaporation of highly alkaline HLW containing aluminum and silicates has produced sodium aluminosilicate scales causing both operation and criticality hazards in the 2H Evaporator System. Segregation of aluminum-rich wastes from silicate-rich wastes minimizes the amount of scale produced and reduces cleaning expenses, but does not eliminate the scaling nor increases operation flexibility in waste process. Similar issues have affected the aluminum refining industry for many decades. Over the past several years, successful commercial products have been identified to eliminate aluminosilicate fouling in the aluminum industry, but have not been utilized in a nuclear environment. Laboratory quantities of three proprietary aluminosilicate scale inhibitors have been produced and been shown to prevent formation of scales. SRNL has been actively testing these potential inhibitors to examine their radiation stability, radiolytic degradation behaviors, and downstream impacts to determine their viability within the HLW system. One of the tested polymers successfully meets the established criteria for application in the nuclear environment. This paper will describe a summary of the methodology used to prioritize laboratory testing protocols based on potential impacts/risks identified for inhibitor deployment at SRS
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Hanford Supplemental Treatment: Literature and Modeling Review of SRS HLW Salt Dissolution and Fractional Crystallization
In order to accelerate waste treatment and disposal of Hanford tank waste by 2028, the Department of Energy (DOE) and CH2M Hill Hanford Group (CHG), Inc. are evaluating alternative technologies which will be used in conjunction with the Waste Treatment Plant (WTP) to safely pretreat and immobilize the tank waste. Several technologies (Bulk Vitrification and Steam Reforming) are currently being evaluated for immobilizing the pretreated waste. Since the WTP does not have sufficient capacity to pretreat all the waste going to supplemental treatment by the 2028 milestone, two technologies (Selective Dissolution and Fractional Crystallization) are being considered for pretreatment of salt waste. The scope of this task was to: (1) evaluate the recent Savannah River Site (SRS) Tank 41 dissolution campaign and other literature to provide a more complete understanding of selective dissolution, (2) provide an update on the progress of salt dissolution and modeling activities at SRS, (3) investigate SRS experience and outside literature sources on industrial equipment and experimental results of previous fractional crystallization processes, and (4) evaluate recent Hanford AP104 boildown experiments and modeling results and recommend enhancements to the Environmental Simulation Program (ESP) to improve its predictive capabilities. This report provides a summary of this work and suggested recommendations
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