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Solvent extraction separation of trivalent lanthanide and actinide ions using an aqueous aminomethanediphosphonic acid.

Description: The possibility of separating the trivalent lanthanides, represented by EU{sup 3+}, and actinides, represented by Cf{sup 3+}, using HDEHP in toluene and an aqueous phase containing N-piperidinomethane-1,1-diphosphotic acid, PMDPA, has been investigated. This modified aqueous phase offers potential advantages over the diethylenetriaminepentaacetic acid based TALSPEAK process because of the improved complexation properties of PMDPA in acidic solutions, and the ability to decompose PMDPA before disposal. Extraction experiments were conducted at 25 C in 2 M NaClO{sub 4} between -log [H{sup +}] 1 and 2. The studies enabled us to derive the aqueous phase speciation, the stability constants of the aqueous complexes, and the Cf/Eu separation factors. Despite the presence of an amino group in PMDPA that should favor the retention of the actinides in the aqueous phase, the Cf/Eu separation factors are near unity under the conditions studied.
Date: October 14, 1998
Creator: Jensen, M. P.
Partner: UNT Libraries Government Documents Department

Analytical-scale separations of lanthanides : a review of techniques and fundamentals.

Description: Separations chemistry is at the heart of most analytical procedures to determine the rare earth content of both man-made and naturally occurring materials. Such procedures are widely used in mineral exploration, fundamental geology and geochemistry, material science, and in the nuclear industry. Chromatographic methods that rely on aqueous solutions containing complexing agents sensitive to the lanthanide cationic radius and cation-exchange phase transfer reactions (using a variety of different solid media) have enjoyed the greatest success for these procedures. In this report, they will briefly summarize the most important methods for completing such analyses. they consider in some detail the basic aqueous (and two-phase) solution chemistry that accounts for separations that work well and offer explanations for why others are less successful.
Date: October 27, 1999
Creator: Nash, K. L. & Jensen, M. P.
Partner: UNT Libraries Government Documents Department

A combined cesium-strontium extraction/recovery process

Description: A new solvent extraction process for the simultaneous extraction of cesium and strontium from acidic nitrate media is described. This process uses a solvent formulation comprised of 0.05 M di-t-butylcyclohexano-18-crown-6 (DtBuCH18C6), 0.1 M Crown 100{prime} (a proprietary, cesium-selective derivative of dibenzo-18-crown-6), 1.2 M tributyl phosphate (TBP), and 5% (v/v) lauryl nitrile in an isoparaffinic hydrocarbon diluent. Distribution ratios for cesium and strontium from 4 M nitric acid are 4.13 and 3.46, respectively. A benchtop batch countercurrent extraction experiment indicates that >98% of the cesium and strontium initially present in the feed solution can be removed in only four extraction stages. Through proper choice of extraction and strip conditions, extracted cesium and strontium can be recovered either together or individually.
Date: March 1, 1996
Creator: Horwitz, E.P.; Dietz, M.L. & Jensen, M.P.
Partner: UNT Libraries Government Documents Department

Characterization of actinides in simulated alkaline tank waste sludges and leach solutions

Description: Current plans call for an alkaline scrub of actinide-bearing sludges in the Hanford Waste tanks prior to their incorporation in glass waste forms. Though it is assumed that actinides will remain in the sludge phase during this procedure, this assumption is based on insufficient supporting thermodynamic and kinetic data. In this project the authors will investigate the fundamental chemistry of actinides in strongly alkaline solution and solid phases to strengthen the foundation and identify potential limitations of this approach. They will focus on the characterization of the leaching of actinides from simulated BiPO{sub 4}, REDOX, and PUREX sludges, the identification of actinide mineral phases in the sludge simulants, and the possible solubilization of actinides by complexation and radiolysis effects. This program will provide new fundamental information on the chemical behavior and speciation of uranium, neptunium, plutonium, and americium in simulated alkaline tank waste sludges and alkaline scrub liquors. Sludge simulants will be prepared from the appropriate matrix components using published data for guidance. Actinide ions will be introduced in the oxidation states pertinent to process conditions. The authors will characterize the speciation of the actinides in the sludges using a variety of techniques. In parallel studies, they will address the chemistry of actinide ions in alkaline solutions, principally those containing chelating agents. The third critical element of this research will be to assess the impact of radiolysis on actinide behavior. By correlating actinide speciation in the solid and solution phases with sludge composition, it will be possible to predict conditions favoring mobilization (or immobilization) of actinide ions during sludge washing. The new information will increase predictability of actinide behavior during tank sludge washing, and so contribute to minimization of the volume of high level waste created.
Date: April 21, 2000
Creator: Nash, K. L.; Rao, L.; Jensen, M. P. & Bond, A. H.
Partner: UNT Libraries Government Documents Department

Actinide immobilization in the subsurface environment by in-situ treatment with a hydrolytically unstable organophosphorus complexant: Uranyl uptake by calcium phytate

Description: In addition to naturally occurring uranium and thorium, actinide ions exist in the subsurface environment as a result of accidental releases and intentional disposal practices associated with nuclear weapons production. These species present a significant challenge to cost-effective remediation of contaminated environments. An attractive approach to decreasing the probability of actinide migration in the subsurface is to transform the ions into a less mobile form by remote treatment. We have under development a process which relies on a polyfunctional organophosphorus complexant to sequester the mobile metal ions by complexation/cation exchange in the near term, and to subsequently decompose, transforming the actinides into insoluble phosphate mineral forms in the long term. Studies to date include identification of a suitable organophosphorus reagent, profiling of its decomposition kinetics, verification of the formation of phosphate mineral phases upon decomposition of the reagent, and extensive comparison of the actinide uptake ability of the calcium salt of the reagent as compared with hydroxyapatite. In this report, we briefly describe the process with focus on the cation exchange behavior of the calcium salt of the organophosphorus sequestrant.
Date: December 31, 1997
Creator: Nash, K.L.; Jensen, M.P. & Schmidt, M.A.
Partner: UNT Libraries Government Documents Department

Stability constants of europium complexes with a nitrogen heterocycle substituted methane-1,1-diphosphonic acid

Description: Even in moderately acidic solutions ([H{sup +}] > 0.01 M), N-piperidinomethane-1,1-diphosphonic acid (H{sub 4}PMDPA) is a strong complexant of trivalent lanthanide ions that shows enhanced complex solubility over previously studied 1,1-diphosphonic acids. The protonation constants of PMDPA in 2.0 M H/NaClO{sub 4} were determined by potentiometric and NMR titrations, and the stability constants for formation of complexes with Eu{sup 3+} were determined by solvent extraction. Difference in protonation equilibria induced by addition of the nitrogen heterocycle results in an increase in the complexation strength of PMDPA. In solutions containing 0.1 M H{sup +} and ligand concentrations greater than 0.02 M, PMDPA is the most effective 1,1-diphosphonic acid for europium complexation studied thus far.
Date: June 1, 1996
Creator: Jensen, M.P.; Rickert, P.G.; Schmidt, M.A. & Nash, K.L.
Partner: UNT Libraries Government Documents Department

Aqueous complexation of trivalent lanthanide and actinide cations by N,N,N'{sub 2},N'-tetrakis(2-pyridylmethyl)ethylenediamine.

Description: The aqueous complexation reactions of trivalent lanthanide and actinide cations with the hexadentate ligand N,N,N{prime},N{prime}-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), have been characterized using potentiometric and spectroscopic techniques in 0.1 M NaClO{sub 4} At 25 C, the stability constant of Am(TPEN){sup 3+} is two orders of magnitude larger than that of Sm(TPEN){sup 3+}, reflecting the stronger interactions of the trivalent actinide cations with softer ligands as compared to lanthanide cations.
Date: June 16, 1999
Creator: Beitz, J. V.; Ensor, D. D.; Jensen, M. P. & Morss, L. R.
Partner: UNT Libraries Government Documents Department

In-situ mineralization of actinides for groundwater cleanup: Laboratory demonstration with soil from the Fernald Environmental Management Project

Description: An attractive approach to decreasing the probability of actinide migration in the subsurface is to transform the ions into less mobile forms by remote treatment. The process described herein relies on a polyfunctional organophosphorus complexant to sequester the mobile metal ions by complexation/cation exchange in the near term. The cation exchanger is designed to subsequently decompose, transforming the actinides into insoluble phosphate mineral forms as the medium of stable long-term isolation. This material can be generated in situ in the subsurface thus eliminating the need for excavation to immobilize the actinide ions. Previous investigations have identified a suitable organophosphorus reagent and profiled its decomposition kinetics, verified the formation of phosphate mineral phases upon decomposition of the reagent, determined solubility limits for appropriate metal phosphates under groundwater conditions, and examined the cation exchange behavior of the calcium salt of the organophosphorus reagent. In this report, the focus is on a laboratory-scale demonstration of the concept using a soil sample from the Fernald Environmental Management Plant.
Date: November 1, 1997
Creator: Nash, K.L.; Jensen, M.P. & Schmidt, M.A.
Partner: UNT Libraries Government Documents Department

Tracking tropical cloud systems for the diagnosis of simulations by the weather research and forecasting (WRF) model

Description: To aid in improving model parameterizations of clouds and convection, we examine the capability of models, using explicit convection, to simulate the life cycle of tropical cloud systems in the tropical warm pool. The cloud life cycle is determined using a satellite cloud tracking algorithm (Boer and Ramanathan, J. Geophys. Res., 1997), and the statistics are compared to those of simulations using the Weather Research and Forecasting (WRF) Model. Using New York Blue, a Blue Gene/L supercomputer that is co-operated by Brookhaven and Stony Brook, simulations are run at a resolution comparable to the observations. Initial results suggest that the organization of the mesoscale convective systems is particularly sensitive to the cloud microphysics parameterization used.
Date: June 27, 2010
Creator: Vogelmann, A.M.; Lin, W.; Cialella, A.; Luke, E. P.; Jensen, M. P.; Zhang, M. H. et al.
Partner: UNT Libraries Government Documents Department

Behavior of actinide ions during sludge washing of alkaline radioactive.

Description: It is difficult to accurately predict actinide behavior during the alkaline leaching of Hanford's radioactive sludges due to the diverse chemical and radiolytic conditions existing in these wastes. The results of Pu dissolution during experimental washing of sludge simulants from the BiPO{sub 4} Redox, and PUREX processes shows that {le} 2.l% Pu is dissolved during contact with alkaline media, but up to 65.5% Pu may be dissolved in acidic media. The dissolution of Cr, Fe, Nd, and Mn has also been observed, and the results of solid state, radioanalytical, and spectroscopic investigations are detailed.
Date: November 15, 1999
Creator: Bond, A. H.; Nash, K. L.; Gelis, A. V.; Jensen, M. P.; Sullivan, J. C. & Rao, L.
Partner: UNT Libraries Government Documents Department

New insights in third phase formation in the U(VI)-HNO{sub 3}, TBP-alkane system.

Description: In this work, the system U(VI)-HNO{sub 3}-tributylphosphate (TBP)-n-dodecane has been revisited with the objective of gaining coordination chemistry and structural information on the species that are formed in the organic phase before and after third phase formation. Chemical analyses, spectroscopic and EXAFS data indicate that U(VI) is extracted as the UO{sub 2}(NO{sub 3}){sub 2} {center_dot} 2TBP adduct, while the third phase species has the composition UO{sub 2}(NO{sub 3}){sub 2} {center_dot} 2TBP {center_dot} HNO{sub 3}. Small-angle neutron scattering (SANS) data reveal the presence in the organic phase, both before and after phase splitting, of ellipsoidal aggregates whose formation seems to depend more on the extraction of HNO{sub 3} than that of U(VI).
Date: June 14, 2001
Creator: Jensen, M. P.; Chiarizia, R.; Ferraro, J. R.; Borkowski, M.; Nash, K. L.; Thiyagarajan, P. et al.
Partner: UNT Libraries Government Documents Department

Midlatitude Continental Convective Clouds Experiment (MC3E)

Description: The Midlatitude Continental Convective Clouds Experiment (MC3E) will take place in central Oklahoma during the April–May 2011 period. The experiment is a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration’s (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign leverages the unprecedented observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation purchased with American Recovery and Reinvestment Act funding. The overarching goal is to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that have never before been available.
Date: April 10, 2010
Creator: Jensen, M. P.; Petersen, W. A.; Del Genio, A. D.; Giangrande, S. E.; Heymsfield, A.; Heymsfield, G. et al.
Partner: UNT Libraries Government Documents Department

Evaluating cloud retrieval algorithms with the ARM BBHRP framework

Description: Climate and weather prediction models require accurate calculations of vertical profiles of radiative heating. Although heating rate calculations cannot be directly validated due to the lack of corresponding observations, surface and top-of-atmosphere measurements can indirectly establish the quality of computed heating rates through validation of the calculated irradiances at the atmospheric boundaries. The ARM Broadband Heating Rate Profile (BBHRP) project, a collaboration of all the working groups in the program, was designed with these heating rate validations as a key objective. Given the large dependence of radiative heating rates on cloud properties, a critical component of BBHRP radiative closure analyses has been the evaluation of cloud microphysical retrieval algorithms. This evaluation is an important step in establishing the necessary confidence in the continuous profiles of computed radiative heating rates produced by BBHRP at the ARM Climate Research Facility (ACRF) sites that are needed for modeling studies. This poster details the continued effort to evaluate cloud property retrieval algorithms within the BBHRP framework, a key focus of the project this year. A requirement for the computation of accurate heating rate profiles is a robust cloud microphysical product that captures the occurrence, height, and phase of clouds above each ACRF site. Various approaches to retrieve the microphysical properties of liquid, ice, and mixed-phase clouds have been processed in BBHRP for the ACRF Southern Great Plains (SGP) and the North Slope of Alaska (NSA) sites. These retrieval methods span a range of assumptions concerning the parameterization of cloud location, particle density, size, shape, and involve different measurement sources. We will present the radiative closure results from several different retrieval approaches for the SGP site, including those from Microbase, the current 'reference' retrieval approach in BBHRP. At the NSA, mixed-phase clouds and cloud with a low optical depth are prevalent; the radiative closure studies ...
Date: March 10, 2008
Creator: Mlawer,E.; Dunn,M.; Mlawer, E.; Shippert, T.; Troyan, D.; Johnson, K. L. et al.
Partner: UNT Libraries Government Documents Department