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Prediction of dissolved actinide concentrations in concentrated electrolyte solutions: a conceptual model and model results for the Waste Isolation Pilot Plant (WIPP)

Description: The conceptual model for WIPP dissolved concentrations is a description of the complex natural and artificial chemical conditions expected to influence dissolved actinide concentrations in the repository. By a set of physical and chemical assumptions regarding chemical kinetics, sorption substrates, and waste-brine interactions, the system was simplified to be amenable to mathematical description. The analysis indicated that an equilibrium thermodynamic model for describing actinide solubilities in brines would be tractable and scientifically supportable. This paper summarizes the conceptualization and modeling approach and the computational results as used in the WIPP application for certification of compliance with relevant regulations for nuclear waste repositories. The WIPP site contains complex natural brines ranging from sea water to 10x more concentrated than sea water. Data bases for predicting solubility of Am(III) (as well as Pu(III) and Nd(III)), Th(IV), and Np(V) in these brines under potential repository conditions have been developed, focusing on chemical interactions with Na, K, Mg, Cl, SO{sub 4}, and CO{sub 3} ions, and the organic acid anions acetate, citrate, EDTA, and oxalate. The laboratory and modeling effort augmented the Harvie et al. parameterization of the Pitzer activity coefficient model so that it could be applied to the actinides and oxidation states important to the WIPP system.
Date: October 25, 1996
Creator: Novak, C.F.; Moore, R.C. & Bynum, R.V.
Partner: UNT Libraries Government Documents Department

Solvent extraction of cesium by substituted crown ethers

Description: The extraction of alkali metal nitrates by 18-crown-6, 21-crown-7, and 24-crown-8 ethers, bearing cyclohexano, benzo-, t-alkylbenzo, and furano- substituents, in 1,2-dichloroethane has been surveyed. Introduction of a furano substituent onto the macrocyclic ring of 18-crown-6 or 21 crown-7 ethers causes a significant reduction in both extraction efficiency and selectivity. Addition of an additional benzo group to dibenzo-21 -crown-7, to give tribenzo-21 -crown-7, decreases both extraction efficiency and selectivity, whereas addition of one or two additional benzo groups to dibenzo-24-crown-8 increases the extraction efficiency and selectivity for the larger ions Rb+ and Cs{sup +} Detailed equilibrium modeling of the extraction by lipophilic 21 -crown-7 ethers indicates that the addition of t-alkyl substituents onto the benzo groups has only a minor effect on the extraction of cesium nitrate by dibenzo-21 -crown-7 ethers.
Date: December 31, 1996
Creator: Sachleben, R.A.; Deng, Y.; Palmer, D.A. & Moyer, B.A.
Partner: UNT Libraries Government Documents Department

Structure within thin epoxy films revealed by solvent swelling: A neutron reflectivity study

Description: The focus of this work is the structure within highly crosslinked, two component epoxy films. The authors examine variations in crosslink density within thin epoxy films on silicon substrates by solvent swelling. The method is based on the fact that the equilibrium volume fraction of a swelling solvent is strongly dependent upon the local crosslink density. The authors examine the volume fraction profile of the good solvent nitrobenzene through the epoxy films by neutron reflection. Isotopic substitution is used to provide contrast between the epoxy matrix and the swelling solvent.
Date: March 2, 2000
Creator: KENT,MICHAEL S.; YIM,HYUN; MCNAMARA,WILLIAM FRERE; IVKOV,R.; SATIJA,S. & MAJEWSKI,J.
Partner: UNT Libraries Government Documents Department

Effect of tetralin on the degradation of polymer in solution

Description: The effect of a hydrogen-donor solvent tetralin on thermal degradation of poly(styrene-allyl alcohol) in liquid solution was investigated in a steady-state tubular flow reactor at 1000 psig at various tetralin concentrations, polymer concentrations, and temperatures. The experimental data were interpreted with continuous- mixture kinetics, and rate coefficients determined for the specific and random degradation processes.
Date: December 31, 1995
Creator: Madras, G.; Smith, J.M. & McCoy, B.J.
Partner: UNT Libraries Government Documents Department

Equilibria and effect of diluent in the solvent extraction of lithium salts by highly alkylated 14-crown-4-ethers

Description: As shown by survey experiments, 14-crown-4 ethers bearing certain aliphatic substituents exhibit strong selectivity for lithium. Both selectivity and overall extraction efficiency depend markedly on type of ring substituents and on diluent properties. To understand such effects in greater detail, extraction of LiCl by the crown ether 2,2,3,3,6,9,9,10,10-nonamethyl-14-crown-4 (NM14C4) was subjected to equilibrium analysis. By use of the program SXLSQI (a solvent-extraction modeling program), the extraction behavior as determined by ion chromatography has been modeled quantitatively in terms of four equilibrium in 1-octanol. The following neutral and ionic organic-phase species have been considered: LiCl, Li+, Cl{sup {minus}}, LiCECl, and LiCE+ (CE = crown ether). Parallel measurements of the same system by {sup 7}Li NMR techniques agree with the ion-chromatography results. The NMR experiment affords the advantage of distinguishing between free and bound lithium and thus provides a check on the species indicated by the modeling. Extraction of LiCl by NM 14C4 correlates with diluent properties, including the Shmidt-Marcus diluent parameter and Reichardt`s E{sub T} parameter; as diluent polarity increases, LiCl extraction increases steeply.
Date: December 31, 1996
Creator: Moyer, B.A.; Sachleben, R.A.; Sun, Y.; Driver, J.L.; Chen, Z. Cavenaugh, K.L.; Carter, R.W. et al.
Partner: UNT Libraries Government Documents Department

Neptunium(V) and neptunium(VI) solubilities in synthetic brines of interest to the Waste Isolation Pilot Plant (WIPP)

Description: The solubility of Np(V) and Np(VI) has been measured in three synthetic Na-K-Mg-Cl brines in the presence of CO{sub 2}(g). Experiments were prepared from oversaturation by adding an excess of NpO{sub 2}{sup +} or NpO{sub 2}{sup 2+} to the brines and allowing the neptunium solids to precipitate. Vessels were maintained in contact with fixed CO{sub 2}(g) partial pressures at constant pH and 24 {+-} 1 C. Dissolved Np(V) concentrations decreased several orders of magnitude within the first 100 days of the experiment, while dissolved Np(VI) concentrations decreased initially but then remained relatively constant for more than 400 days. The solid phases formed in all experiments were identified by X-ray powder diffraction as KNpO{sub 2}CO{sub 3}{center_dot}xH{sub 2}O(s). Steady state concentrations for Np(V) are similar to those observed for Pu(V) in the same brines under the same conditions, where Pu occurs predominantly as Pu(V). Similarly, steady state concentrations for Np(VI), which was not reduced over a two year period, compare well with measured Pu(VI) concentrations in the same brines before the Pu(VI) was reduced to Pu(V).
Date: December 31, 1996
Creator: Novak, C. F.; Nitsche, H. & Silber, H. B.
Partner: UNT Libraries Government Documents Department

Evaluation of aqueous cleaners as alternatives to vapor degreasing

Description: As part of the preparation process during assembly of thermally activated batteries, the stainless steel piece parts are normally cleaned by vapor degreasing with trichloroethylene. Severe restrictions on the use of chlorinated and fluorinated hydrocarbons in recent years prompted the evaluation of a number of aqueous cleaners as a replacement technology for this application. A total of seven commercial aqueous degreasers was evaluated in this study at several dilution ratios and temperatures. One organic cleaner was also examined under ambient conditions. The effectiveness of the cleaner was determined by the use of x-ray photoelectron spectroscopy (XPS), which is a surface analytical technique that is very sensitive to low levels of surface contaminants. A quartz-crystal microbalance (QCM) that is immersed in the cleaning bath was evaluated as a tool for monitoring the bath cleanliness. The best overall cleaning results were obtained with Micro, Impro-Clean 3800, and Sonicor cleaners.
Date: May 1, 1996
Creator: Guidotti, R.A.; Schneider, T.W. & Frye, G.C.
Partner: UNT Libraries Government Documents Department

Reclamation and reuse of freon in total petroleum hydrocarbon analyses

Description: ADS is using a commercially available solvent reclamation system to recycle 95-97 percent of the Freon used in total petroleum hydrocarbon analyses. ADS has further developed the commercially available solvent reclamation system to accommodate radioactive contaminated Freon. This report establishes the following: validity of the method; success of recycling; and effect of radionuclides in recycling radioactive contaminated Freon. The standard analysis method for determining total petroleum hydrocarbons (commonly known as oil and grease determination) involves solvent extraction of the hydrocarbons using Freon followed by quantitation using infrared detection. This has been the method of choice because it is simple, rugged, inexpensive, and applicable to both solid and liquid samples and to radioactive samples. Due to its deleterious effect on the ozone layer, the use of Freon and other chloro-fluorocarbons (CFCs) has been greatly restricted. Freon has become very expensive (800$/liter) and will soon be unavailable entirely. Several methods have been proposed to replace the Freon extraction method. These methods include solid-phase extraction, solvent extraction, and supercritical fluid extraction all of which use gravimetric determination or infrared analysis of the extracted hydrocarbons. These methods are not as precise or as sensitive as the Freon extraction method, and a larger amount of sample is therefore required due to the decreased sensitivity. The solid phase extraction method cannot accommodate solid samples. Supercritical fluid extraction requires expensive instrumentation. ADS opted to keep the existing Freon method and recycle the solvent. An inexpensive solvent reclamation system was procured to reclaim the spent Freon. This reclaimer removes hydrocarbons from the Freon solvent by passage through an activated carbon bed.
Date: April 1, 1996
Creator: Ekechukwu, A.A. & Peterson, S.F.
Partner: UNT Libraries Government Documents Department

Swelling behavior of O-alkylated APCS coals as examined by the EPR spin probe method

Description: Known O-alkylation procedures have been used to derivatize the carboxyl and hydroxyl groups in the APCS coals Lewiston-Stockton, Wyodak-Anderson, Beulah-Zap, Illinois {number_sign}6, Upper Freeport, and Pittsburgh {number_sign}8. In general the resulting decrease in hydrogen bonding reduced the cyclical variation in nitroxide spin probe retention observed for nonalkylated coals when small amounts (<1%) of pyridine are present in the toluene swelling solvent. An increase in spin probe retention by the O-alkylated coals relative to the underivatized coals indicates a more open arrangement in the coal due to a decrease in attractive forces, confirming that microporosity increases with increasing rank.
Date: December 31, 1995
Creator: Ding, Ruisong; Tucker, D. & Kispert, L.D.
Partner: UNT Libraries Government Documents Department

Improvement of hydrogen solubility and entrainment in hydrocracker feedstocks. Final technical report

Description: The project consisted of two tasks: (1) development of a thermodynamic model for hydrogen solubility in hydrocarbons and extension of this model to predict solubility of hydrogen in hydrocracker feedstocks at conditions similar to those of hydrocracking operations, and (2) design and construction of a gas solubility apparatus to measure solubility of hydrogen in hydrocarbons and in hydrocracker feedstocks. The theoretical work proposed was fully accomplished by developing a sophisticated model for hydrogen solubility in hydrocarbons and in hydrocracker feedstocks at advanced temperatures and pressures. The proposed experimental work ran into a number of obstacles, especially to get the original and newly designed on-line sampling technique to function properly. A number of calibrations and tests for reproducibility were necessary to assure the accuracy of measured data. Although a very well designed gas solubility apparatus was built, not much time was left to generate significant hydrogen solubility data. The plans are to use the apparatus in future to measure hydrogen solubility data in liquid fuels to facilitate more efficient design of fuel conversion systems.
Date: February 1, 1997
Creator: Kabadi, V.N.
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering studies of coal-extract solutions

Description: Interest in the physics and chemistry of coal extracts has extended for over 100 years. Early on it was recognized that pyridine was a particularly good solvent capable of extracting a significant weight percent of intermediate rank coals. Many of the current theories regarding the macromolecular structure of coals (type III kerogens) are based on the fact that there exists a physically definable limit in the extractability of soluble organics from coal in pyridine. The non-extractable residue is generally considered to be a cross-linked macromolecular network. The extract-solvent {open_quotes}solutions{close_quotes}, although acknowledged to be far from ideal (thermodynamically), are presumed to be {open_quotes}molecular solutions{close_quotes} in the sense that random mixing of the constituents occurs within a single solution phase. This research set out to characterize the solution structures of coal extracts to gain insight into the nature of coal-solvent interactions.
Date: August 1, 1997
Creator: Thiyagarajan, P. & Cody, G.D.
Partner: UNT Libraries Government Documents Department

Dried plutonium nitrate decontamination using HNO{sub 3} or Freon 113

Description: A request was made of the Separations Technology Laboratory to perform tests to determine the relative effectiveness of Freon 113 and 18% (3.15M) nitric acid on removing dried plutonium nitrate from Hypalon{reg_sign} gloves destined for use in F B-Line. Freon 113 was very inefficient for removing dried plutonium nitrate under conditions of moderate agitation of the liquid in contact with the dried compound. Nitric acid proved to be an excellent agent for decontaminating purposes for both the gloves and for the Pyrex glass. In tests conducted on the glass or on the gloves on which dried plutonium nitrate had not been removed by Freon 113, followup with nitric acid efficiently removed the residual plutonium nitrate. Tests were also conducted to give some measure of the resistance of the Hypalon glove to continuous contact with 18% HNO{sub 3} or with Freon 113. Following two weeks` immersion, there was little physical difference noted from the starting material, except the glove piece immersed in the Freon underwent an 8% weight gain.
Date: February 4, 1988
Creator: Holcomb, H. P.
Partner: UNT Libraries Government Documents Department

Transition metal catalyzed polymerization of butadiene in supercritical CO{sub 2}

Description: A class of Ni(II) catalysts has been shown to stereoselectively catalyze the 1,4-polymerization of butadiene. The authors have been investigating the use of supercritical CO{sub 2} as an environmentally benign replacement solvent for conventional hydrocarbon and halocarbon solvents for a variety of chemical transformations. Above 31 C, CO{sub 2} enters a supercritical phase, where its physical properties are both liquid-like and gas-like. Importantly, the solvent properties such as dielectric constant for supercritical fluids can be varied by changing the pressure of the fluid. In this report, the authors present results of an investigation of the polymerization of 1,3-butadiene using [({pi}-allyl) Ni(CF{sub 3}CO{sub 2})]{sub 2} in supercritical CO{sub 2}. They conducted 1,3-butadiene polymerizations in CO{sub 2} to determine whether or not they could systematically and predictably adjust the regiochemistry/stereochemistry of the polybutadiene product by varying the solution properties at different pressures. They also mention experiments with CO catalysts that are known to give 1,2-syndiotactic polybutadiene, and with a Pd catalyst system that is known to copolymerize olefin with CO to give perfectly alternating copolymers.
Date: August 1, 1998
Creator: Borkowsky, S.; Tumas, W. & Waymouth, R.M.
Partner: UNT Libraries Government Documents Department

Liquid metal extraction of Nd from NdFeB magnet scrap

Description: This research involves using molten magnesium (Mg) to remove neodymium (Nd) from NdFeB magnet scrap by diffusion. The results show that liquid metal extraction of Nd may be a viable and inexpensive method for recovering the expensive rare earth element Nd for use in Mg castings.
Date: December 10, 1999
Creator: Xu, Yanchen
Partner: UNT Libraries Government Documents Department

Photochemical coal dissolution. Quarterly technical progress report, July 1--September 30, 1995

Description: Examination of the photochemical extractions of the four Argonne Premium Coal Residues has been under way in a routine manner during this last quarter. An unexpectedly great effort last quarter had been necessary to find extraction solvents and photochemical reagents that were photochemically stable and inert. While it is a rather poor thermal extraction solvent, acetonitrile has proven to be the best solvent the authors have examined. In addition to runs with only the acetonitrile solvent present, experiments were performed with the photochemical reagents, benzophenone and pyridine. Both ketone and pyridine triplet states are well-known for their hydrogen abstraction and electron transfer capabilities. The photochemical reagents were used at concentrations resulting in 50% transmission of the light across the reactor pathlength at 320 nm. Experiments with the quartz cutoff filter remain to be completed at concentrations resulting in 50% transmittance at lower wavelengths. Changes in the transmission of light by the column effluent were monitored continuously and the extraction yield by weight was measured by evaporation of the solvent and subtraction of reagent weight. Thermal extraction yields without light under otherwise identical conditions were measured for comparison. As a check on undesirable effects, such as solvent photochemical degradation, otherwise identical light and dark experiments were also done without the coal on the column.
Date: December 31, 1995
Creator: Doetschman, D.C.
Partner: UNT Libraries Government Documents Department

Final Report for Fractionation and Separation of Polydisperse Nanoparticles into Distinct Monodisperse Fractions Using CO2 Expanded Liquids

Description: The overall objective of this project was to facilitate efficient fractionation and separation of polydisperse metal nanoparticle populations into distinct monodisperse fractions using the tunable solvent properties of gas expanded liquids. Specifically, the dispersibility of ligand-stabilized nanoparticles in an organic solution was controlled by altering the ligand-solvent interaction (solvation) by the addition of carbon dioxide (CO{sub 2}) gas as an antisolvent (thereby tailoring the bulk solvent strength) in a custom high pressure apparatus developed in our lab. This was accomplished by adjusting the CO{sub 2} pressure over the liquid dispersion, resulting in a simple means of tuning the nanoparticle precipitation by size. Overall, this work utilized the highly tunable solvent properties of organic/CO{sub 2} solvent mixtures to selectively size-separate dispersions of polydisperse nanoparticles (ranging from 1 to 20 nm in size) into monodisperse fractions ({+-}1nm). Specifically, three primary tasks were performed to meet the overall objective. Task 1 involved the investigation of the effects of various operating parameters (such as temperature, pressure, ligand length and ligand type) on the efficiency of separation and fractionation of Ag nanoparticles. In addition, a thermodynamic interaction energy model was developed to predict the dispersibility of different sized nanoparticles in the gas expanded liquids at various conditions. Task 2 involved the extension of the experimental procedures identified in task 1 to the separation of other metal particles used in catalysis such as Au as well as other materials such as semiconductor particles (e.g. CdSe). Task 3 involved using the optimal conditions identified in tasks 1 and 2 to scale up the process to handle sample sizes of greater than 1 g. An experimental system was designed to allow nanoparticles of increasingly smaller sizes to be precipitated sequentially in a vertical series of high pressure vessels by moving the liquid nanoparticle dispersion from the top vessel ...
Date: August 31, 2007
Creator: Roberts, Chistopher
Partner: UNT Libraries Government Documents Department