3,599 Matching Results

Search Results

Advanced search parameters have been applied.

THE DISCOVERY OF THE TRANSURANIUM ELEMENTS: THEIR HISTORY AND A PRESENTATION OF THE DIFFERENT METHODS USED IN THEIR DISCOVERY

Description: BS>The ten transuranium elements discovered since 1940 are discussed in chronological order. The discoverer, the history, and methods used are given for each element. Future developments in the discovery and preparation of transuranic elements are discussed. (A.C.)
Date: April 1, 1959
Creator: Thompson, S.G.
Partner: UNT Libraries Government Documents Department

The Estimation of Heats of Formation

Description: The procedure for estimation of heats of formation of compounds is illustrated by discussion of compounds of several of the elements of the actinide series. The procedure is particularly suited for lanthanide and actinide elements because of the similarity of the ionic radii and types of bonding.
Date: February 2, 1948
Creator: Brewer, Leo
Partner: UNT Libraries Government Documents Department

Complexation of Actinides in Solution: Thermodynamic Measurementsand Structural Characterization

Description: This paper presents a brief introduction of the studies of actinide complexation in solution at Lawrence Berkeley National Laboratory. An integrated approach of thermodynamic measurements and structural characterization is taken to obtain fundamental understanding of actinide complexation in solution that is of importance in predicting the behavior of actinides in separation processes and environmental transport.
Date: February 1, 2007
Creator: Rao, L.
Partner: UNT Libraries Government Documents Department

Complexation of Gluconate with Uranium(VI) in Acidic Solutions: Thermodynamic Study with Structural Analysis

Description: Within the pC{sub H} range of 2.5 to 4.2, gluconate forms three uranyl complexes UO{sub 2}(GH{sub 4}){sup +}, UO{sub 2}(GH{sub 3})(aq), and UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -}, through the following reactions: (1) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 4}){sup +}, (2) UO{sub 2}{sup 2+} + GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(aq) + H{sup +}, and (3) UO{sub 2}{sup 2+} + 2GH{sub 4}{sup -} = UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -} + H{sup +}. Complexes were inferred from potentiometric, calorimetric, NMR, and EXAFS studies. Correspondingly, the stability constants and enthalpies were determined to be log {Beta}{sub 1} = 2.2 {+-} 0.3 and {Delta}H{sub 1} = 7.5 {+-} 1.3 kJ mol{sup -1} for reaction (1), log {Beta}{sub 2} = -(0.38 {+-} 0.05) and {Delta}H{sub 2} = 15.4 {+-} 0.3 kJ mol{sup -1} for reaction (2), and log {Beta}{sub 3} = 1.3 {+-} 0.2 and {Delta}H{sub 3} = 14.6 {+-} 0.3 kJ mol{sup -1} for reaction (3), at I = 1.0 M NaClO{sub 4} and t = 25 C. The UO{sub 2}(GH{sub 4}){sup +} complex forms through the bidentate carboxylate binding to U(VI). In the UO{sub 2}(GH{sub 3})(aq) complex, hydroxyl-deprotonated gluconate (GH{sub 3}{sup 2-}) coordinates to U(VI) through the five-membered ring chelation. For the UO{sub 2}(GH{sub 3})(GH{sub 4}){sup -} complex, multiple coordination modes are suggested. These results are discussed in the context of trivalent and pentavalent actinide complexation by gluconate.
Date: January 5, 2009
Creator: Zhang, Zhicheng; Helms, G.; Clark, S. B.; Tian, Guoxin; Zanonato, PierLuigi & Rao, Linfeng
Partner: UNT Libraries Government Documents Department

Chemical speciation of strontium, americium, and curium in high level waste: Predictive modeling of phase partitioning during tank processing. 1998 annual progress report

Description: 'In this research program, Pacific Northwest National Laboratory (PNNL) and Florida State University (FSU) are investigating the speciation of Sr and Am/Cm in the presence of selected organic chelating agents (ethylenediaminetetraacetic acid (EDTA), N-(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA), nitrilotriacetic acid (NTA), and iminodiacetic acid (IDA)) over ranges of hydroxide, carbonate, ionic strength, and competing metal ion concentrations present in high level waste tanks. The fundamental understanding of chemical speciation reactions gained from these studies is also used to propose methodologies for removal of Sr and Am/Cm from organic chelates present in high level tank waste, via competition, displacement or other reactions, without the need for the development of costly and potentially hazardous organic destruction technologies.'
Date: June 1, 1998
Creator: Felmy, A. R.
Partner: UNT Libraries Government Documents Department

United States Transuranium and Uranium Registries. Annual report October 1, 1994 - September 30, 1995

Description: The United States Transuranium and Uranium Registries (USTUR) comprise a human tissue research program studying the deposition, biokinetics and dosimetry of the actinide elements in humans with the primary goals of providing data fundamental to the verification, refinement, or future development of radiation protection standards for these and other radionuclides, and of determining possible bioeffects on both a macro and subcellular level attributable to exposure to the actinides. This report covers USTUR activities during the year from October 1994 through September 1995.
Date: July 1, 1996
Creator: Kathren, R.L.; Harwick, L.A. & Markel, M.J.
Partner: UNT Libraries Government Documents Department

United States Transuranium and Uranium Registries. Annual report February 1, 2000--January 31, 2001

Description: The United States Transuranium and Uranium Registries (USTUR) comprise a human tissue research program studying the deposition, biokinetics and dosimetry of the actinide elements in humans with the primary goals of providing data fundamental to the verification, refinement, or future development of radiation protection standards for these and other radionuclides, and of determining possible bioeffects on both a macro and subcellular level attributable to exposure to the actinides. This report covers USTUR activities during the year from February 2000 through January 2001.
Date: July 1, 2001
Creator: Ehrhart, Susan M. (ed.) & Filipy, Ronald E. (ed.)
Partner: UNT Libraries Government Documents Department

United States Transuranium and Uranium Registries. Annual report February 1, 2001--January 31, 2002

Description: This report documents the activities of the United States Transuranium and Uranium Registries (USTUR) from February 2001 through January 2002. Progress in continuing collaborations and several new collaborations is reviewed.
Date: July 1, 2002
Creator: Ehrhart, Susan M. & Filipy, Ronald E. (ed)
Partner: UNT Libraries Government Documents Department

Final Technical Progress Report Long term risk from actinides in the environment: Modes of mobility

Description: The key source of uncertainty in assessing actinide mobility is the relative importance of transport by: (1) wind erosion, (2) water erosion, and (3) vertical migration. Each of these three processes depends on several environmental factors and they compete with one another. A scientific assessment of the long-term risks associated with actinides in surface soils depends on better quantifying each of these three modes of mobility. The objective from our EMSP study was to quantify the mobility of soil actinides by wind erosion, water erosion, and vertical migration at three semiarid sites where actinide mobility is a key technical, social and legal issue. This EMSP project was the first to evaluate all three factors at a site. The approach has been to investigate both short- and long-term issues based on field and lab studies and model comparisons. Our results demonstrate the importance of incorporating threshold responses into a modeling framework that accounts for environmental factors and natural disturbances that trigger large changes in actinide mobility. The study measured erosional losses of sediment and fallout cesium (an actinide analogue) from field plots located near WIPP in 1998. The results highlight the large effect of burning as a disturbance on contaminant transport and mobility via runoff and erosion. The results show that runoff, erosion, and actinide transport are (1) strongly site specific-differences in radionuclide transport between WIPP and Rocky Flats differed by a factor of twelve because of soil and vegetation differences, and (2) are strongly impacted by disturbances such as fire, which can increase runoff, erosion, and actinide transport by more than an order of magnitude. In addition, a laboratory experiment using soil columns was conducted to investigate the vertical transport of contaminants in sandy soils. Nine columns of soil collected from the vicinity of the WIPP site were prepared. The ...
Date: March 22, 2002
Creator: Kirchner, Thomas B.
Partner: UNT Libraries Government Documents Department

Toward understanding the thermodynamics of TALSPEAK process. Medium effects on actinide complexation

Description: The ingenious combination of lactate and diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA) as an aqueous actinide-complexing medium forms the basis of the successful separation of americium and curium from lanthanides known as the TALSPEAK process. While numerous reports in the prior literature have focused on the optimization of this solvent extraction system, considerably less attention has been devoted to the understanding of the basic thermodynamic features of the complex fluids responsible for the separation. The available thermochemical information of both lactate and DTPA protonation and metal complexation reactions are representative of the behavior of these ions under idealized conditions. Our previous studies of medium effects on lactate protonation suggest that significant departures from the speciation predicted based on reported thermodynamic values should be expected in the TALSPEAK aqueous environment. Thermodynamic parameters describing the separation chemistry of this process thus require further examination at conditions significantly removed from conventional ideal systems commonly employed in fundamental solution chemistry. Such thermodynamic characterization is the key to predictive modelling of TALSPEAK. Improved understanding will, in principle, allow process technologists to more efficiently respond to off-normal conditions during large scale process operation. In this report, the results of calorimetric and potentiometric investigations of the effects of aqueous electrolytes on the thermodynamic parameters for lactate protonation and lactate complexation of americium and neodymium will be presented. Studies on the lactate protonation equilibrium will clearly illustrate distinct thermodynamic variations between strong electrolyte aqueous systems and buffered lactate environment.
Date: July 1, 2009
Creator: Zalupski, Peter R; Martin, Leigh R; Nash, Ken; Nakamura, Yoshinobu & Yamamoto, Masahiko
Partner: UNT Libraries Government Documents Department

Actinide Targets for Neutron Cross Section Measurements

Description: The Advanced Fuel Cycle Initiative (AFCI) and the Generation IV Reactor Initiative have demonstrated a lack of detailed neutron cross-sections for certain "minor" actinides, those other than the most common (235U, 238U, and 239Pu). For some closed-fuel-cycle reactor designs more than 50% of reactivity will, at some point, be derived from "minor" actinides that currently have poorly known or in some cases not measured (n,?) and (n,f) cross sections. A program of measurements under AFCI has begun to correct this. One of the initial hurdles has been to produce well-characterized, highly isotopically enriched, and chemically pure actinide targets on thin backings. Using a combination of resurrected techniques and new developments, we have made a series of targets including highly enriched 239Pu, 240Pu, and 242Pu. Thus far, we have electrodeposited these actinide targets. In the future, we plan to study reductive distillation to achieve homogeneous, adherent targets on thin metal foils and polymer backings. As we move forward, separated isotopes become scarcer, and safety concerns become greater. The chemical purification and electodeposition techniques will be described.
Date: October 1, 2006
Creator: Baker, John D. & McGrath, Christopher A.
Partner: UNT Libraries Government Documents Department

Separation of Minor Actinides from Lanthanides by Dithiophosphinic Acid Extractants

Description: The selective extraction of the minor actinides (Am(III) and Cm(III)) from the lanthanides is an important part of advanced reprocessing of spent nuclear fuel. This separation would allow the Am/Cm to be fabricated into targets and recycled to a reactor and the lanthanides to be dispositioned. This separation is difficult to accomplish due to the similarities in the chemical properties of the trivalent actinides and lanthanides. Research efforts at the Idaho National Laboratory have identified an innovative synthetic pathway yielding new regiospecific dithiophosphinic acid (DPAH) extractants. The synthesis provides DPAH derivatives that can address the issues concerning minor actinide separation and extractant stability. For this work, two new symmetric DPAH extractants have been prepared. The use of these extractants for the separation of minor actinides from lanthanides will be discussed.
Date: September 1, 2008
Creator: Peterman, D. R.; Greenhalgh, M. R.; Tillotson, R. D.; Klaehn, J. R.; Harrup, M. K.; Luther, T. A. et al.
Partner: UNT Libraries Government Documents Department

Radiolysis of actinides and technetium in alkaline media

Description: The {gamma}-radiolysis of aerated alkaline aqueous solutions of Np(V), Np(VI), Pu(VI), Tc(IV), Tc(V), and TC(VII) was studied in the absence of additives and in the presence of CO{sub 3}{sup 2-}, NO{sub 3}{sup -}, NO{sub 2}{sup -}, EDTA, formate, and other organic compounds. The radiolytic reduction of Np(V), Np(VI), Pu(VI), and TC(VII) under different experimental conditions was examined in detail. The addition of EDTA, formate, and alcohols was found to considerably increase the radiation-chemical reduction yields. The formation of the Np(V) peroxo complex was observed in the {gamma}-radiolysis of alkaline aqueous solutions of Np (VI) in the presence of nitrate.
Date: July 10, 1996
Creator: Delegard, C. H.
Partner: UNT Libraries Government Documents Department

Speciation, Mobility and Fate of Actinides in the Groundwater at the Hanford Site (Sept. 1999-Sept. 2002)

Description: The objectives of this project are: (1) the determination of the speciation of plutonium and other actinides (Np, U) in groundwater at the 100 and 200 areas at the Hanford Site. This includes the separation of Pu into particulate, colloidal and <1 kilo-Dalton dissolved phases and the determination of redox states and isotopic composition in each fraction; (2) the characterization of groundwater colloids, which includes submicron-sized inorganic particles and organic macromolecules (3) the prediction of the rate of transport and fate of actinides in the groundwater of the Hanford Site using a three-phase (dissolved-colloid-particulate) model.
Date: May 31, 2001
Creator: Buesseler, K. O.; Dai, M. & Repeta, D. J.
Partner: UNT Libraries Government Documents Department

Measurement of plutonium and other actinide elements at the center for accelerator mass spectrometry: a comparative assessments of competing techniques

Description: Low-level measurements of the long-lived actinide isotopes have a number of important applications throughout the DOE complex. These include radiobioassay programs, environmental assessments, characterization of radioactive wastes, evaluation of waste storage and treatment options, environmental remediation, basic research in chemistry and geochemistry, and other specialized non- proliferation and national security applications. As an example, it has been estimated that for the next few decades more than 1 million radiochemical analyses per year will be needed in support of US efforts to remediate the legacy of radioactive waste generated by weapons production and the nuclear power industry (Crain, 1996). Traditional radiometric counting methods do not have sufficient sensitivity to address many of these requirements. There is also a growing need to evaluate and monitor exposures to DOE workers involved in decommissioning, environmental management and/or remediation of contaminated sites and facilities. Quantitative measurements based on low-level detection techniques are of particular interest in the validation of radionuclide transport models and improving radiation dosimetry/risk estimates. Quantitative data and information are required to assess the potential health-effects of exposures occurring under special conditions (e.g., resuspension/inhalation of high-specific activity particles), of inhomogeneous radiation exposure and assessment of associated dose distributions to different parts of the body/tissue, of low dose exposure, and to validate and/or develop new and improved dosimetry models. Atom counting technology has now developed sufficiently to provide substantially better sensitivity than ionizing radiation detectors for selected long- lived radionuclides. Clearly the development of a robust, high-throughput, highly sensitive actinide measurement capability based on this new technology would have broad and sustainable impact on a range of DOE initiatives. One potential measurement technique for meeting these requirements is accelerator mass spectrometry (AMS). AMS is a widely accepted analytical technique for measurement of isotopes such as 14 C, 26 Al, 36 Cl (Vogel et al., ...
Date: February 1, 1999
Creator: Hamilton, T H & McAninch, J
Partner: UNT Libraries Government Documents Department

Private Sector Initiative Between the U.S. and Japan

Description: OAK-A258 Private Sector Initiative Between the U.S. and Japan. This report for calendar years 1993 through September 1998 describes efforts performed under the Private Sector Initiatives contract. The report also describes those efforts that have continued with private funding after being initiated under this contract. The development of a pyrochemical process, called TRUMP-S, for partitioning actinides from PUREX waste, is described in this report. This effort is funded by the Central Research Institute of Electric Power Industry (CRIEPI), KHI, the United States Department of Energy, and Boeing.
Date: September 30, 1998
Partner: UNT Libraries Government Documents Department