1,374 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Actinide Compounds"  
Results: 1 - 24 next

Fusion Techniques for the Oxidation of Refractory Actinide Oxides

Description: Small-scale experiments were performed to demonstrate the feasibility of fusing refractory actinide oxides with a series of materials commonly used to decompose minerals, glasses, and other refractories as a pretreatment to dissolution and subsequent recovery operations. In these experiments, 1-2 g of plutonium or neptunium oxide (PuO<sub>2</sub> or NpO<sub>2</sub>) were calcined at 900 degrees Celsius, mixed and heated with the fusing reagent(s), and dissolved. For refractory PuO<sub>2</sub>, the most effective material tested was a lithium carbonate (Li<sub>2</sub>CO<sub>3</sub>)/sodium tetraborate (Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub>) mixture which aided in the recovery of 90 percent of the plutonium. The fused product was identified as a lithium plutonate (Li<sub>3</sub>PuO<sub>4</sub>) by x-ray diffraction. The use of a Li<sub>2</sub>CO<sub>3</sub>/Na<sub>2</sub>B<sub>4</sub>O<sub>7</sub> mixture to solubilize high-fired NpO<sub>2</sub> was not as effective as demonstrated for refractory PuO<sub>2</sub>. In a small-scale experiment, 25 percent of the NpO<sub>2</sub> was oxidized to a neptunium (VI) species that dissolved in nitric acid. The remaining neptunium was then easily recovered from the residue by fusing with sodium peroxide (Na<sub>2</sub>O<sub>2</sub>). Approximately 70 percent of the neptunium dissolved in water to yield a basic solution of neptunium (VII). The remainder was recovered as a neptunium (VI) solution by dissolving the residue in 8M nitric acid. In subsequent experiments with Na<sub>2</sub>O<sub>2</sub>, the ratio of neptunium (VII) to (VI) was shown to be a function of the fusion temperature, with higher temperatures (greater than approximately 400 degrees C) favoring the formation of neptunium (VII). The fusion of an actual plutonium-containing residue with Na<sub>2</sub>O<sub>2</sub> and subsequent dissolution was performed to demonstrate the feasibility of a pretreatment process on a larger scale. Sodium peroxide was chosen due to the potential of achieving higher actinide recoveries from refractory materials. In this experiment, nominally 10 g of a graphite-containing residue generated during plutonium casting operations was initially calcined to remove the graphite. Removal of combustible material prior ...
Date: April 15, 1999
Creator: Rudisill, T.S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Decontamination of matrices containing actinide oxides

Description: There is provided a method for removing actinides and actinide oxides, particularly fired actinides, from soil and other contaminated matrices, comprising: (a) contacting a contaminated material with a solution of at least one inhibited fluoride and an acid to form a mixture; (b) heating the mixture of contaminated material and solution to a temperature in the range from about 30 C to about 90 C while stirring; (c) separating the solution from any undissolved matrix material in the mixture; (d) washing the undissolved matrix material to remove any residual materials; and (e) drying and returning the treated matrix material to the environment.
Date: December 1, 1997
Creator: Villarreal, Robert
Item Type: Refine your search to only Patent
Partner: UNT Libraries Government Documents Department

Use of high gradient magnetic separation for actinide application

Description: Decontamination of materials such as soils or waste water that contain radioactive isotopes, heavy metals, or hazardous components is a subject of great interest. Magnetic separation is a physical separation process that segregates materials on the basis of magnetic susceptibility. Because the process relies on physical properties, separations can be achieved while producing a minimum of secondary waste. Most traditional physical separation processes effectively treat particles larger than 70 microns. In many situations, the radioactive contaminants are found concentrated in the fine particle size fraction of less than 20 microns. For effective decontamination of the fine particle size fraction most current operations resort to chemical dissolution methods for treatment. High gradient magnetic separation (HGMS) is able to effectively treat particles from 90 to {approximately}0.1 micron in diameter. The technology is currently used on the 60 ton per hour scale in the kaolin clay industry. When the field gradient is of sufficiently high intensity, paramagnetic particles can be physically captured and separated from extraneous nonmagnetic material. Because all actinide compounds are paramagnetic, magnetic separation of actinide containing mixtures is feasible. The advent of reliable superconducting magnets also makes magnetic separation of weakly paramagnetic species attractive. HGMS work at Los Alamos National Laboratory (LANL) is being developed for soil remediation, waste water treatment and treatment of actinide chemical processing residues. LANL and Lockheed Environmental Systems and Technologies Company (LESAT) have worked on a co-operative research and development agreement (CRADA) to develop HGMS for radioactive soil decontamination. The program is designed to transfer HGMS from the laboratory and other industries for the commercial treatment of radioactive contaminated materials. 9 refs., 2 figs., 2 tabs.
Date: August 1, 1996
Creator: Avens, L.R.; Worl, L.A. & Padilla, D.D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Early actinide organonitrile compounds and their reactivity.

Description: The actinide trihalides are an important class of materials . Anhydrous AnX3 compounds have been prepared via high temperature synthetic techniques, but they exis t as polymeric solids, which are insoluble in organic solvents . 1-3 Transuranic complexe s AnI3(THF)X have been prepared by the reaction of metals with CZH4IZ in THF solution s (An = Pu, x = 5; An = Np, x = 4) 4 and can be viewed as a net oxidation of An metal wit h 1 .5 equivalents molecular iodine. A convenient preparation of organic solvent soluble trivalent actinide compounds has been described where 1 .5 equivalents of IZ are added t o actinide (An) metal turnings (An = Pu, U, Np) suspended in aprotic organic coordinatin g solvent. 5,6 Since virtually all nonaqueous An(III) complexes have been prepared throug h the triodide-tetrahydrofuran complex, we are interested in preparing complexes wit h solvents other than tetrahydrofuran . And, since uranium is often used as a surrogate for studying the chemistry of transuranic actinides, we are seeking to elucidate the chemical differences between the transuranic elements and uranium .
Date: January 1, 2003
Creator: Enriquez, A. E. (Alejandro E.); Matonic, J. H. (John H.); Scott, B. L. (Brian L.) & Neu, M. P. (Mary P.)
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Assigning mass values to in-house standard UF/sub 6/ cylinders

Description: A statistical experimental design called the Fast 4-1 Series is used to assign mass values to in-house standard UF/sub 6/ cylinders. This design is intended to minimize the number of weighings of large cylinders yet provide acceptable estimates of mass values and their precision. 5 refs.
Date: January 1, 1987
Creator: Goldman, A.; McGuire, D. & Croarkin, C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Structural and magnetic characterization of actinide materials

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors have successfully used neutron scattering techniques to investigate physicochemical properties of elements, compounds, and alloys of the light actinides. The focus of this work is to extend the fundamental research capability and to address questions of practical importance to stockpile integrity and long-term storage of nuclear material. Specific subject areas are developing neutron diffraction techniques for smaller actinide samples; modeling of inelastic scattering data for actinide metal hydrides; characterizing actinide oxide structures; and investigating aging effects in actinides. These studies utilize neutron scattering supported by equilibrium studies, kinetics, and x-ray diffraction. Major accomplishments include (1) development of encapsulation techniques for small actinide samples and neutron diffraction studies of AmD{sub 2.4} and PuO{sub 2.3}; (2) refinement of lattice dynamics model to elucidate hydrogen-hydrogen and hydrogen-metal interactions in rare-earth and actinide hydrides; (3) kinetic studies with PuO{sub 2} indicating that the recombination reaction is faster than radiolytic decomposition of adsorbed water but a chemical reaction produces H{sub 2}; (4) PVT studies of the reaction between PuO{sub 2} and water demonstrate that PuO{sub 2+x} and H{sub 2} form and that PuO{sub 2} is not the thermodynamically stable form of the oxide in air; and (5) model calculations of helium in growth in aged plutonium predicting bubble formation only at grain boundaries at room temperature. The work performed in this project has application to fundamental properties of actinides, aging, and long-term storage of plutonium.
Date: December 31, 1998
Creator: Cort, B.; Allen, T.H. & Lawson, A.C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

The relative radiation resistance of zirconolite, pyrochlore and perovskite to 1.5 MeV Kr{sup +} ions

Description: Zirconolite (CaZrTi2O7), pyrochlore (VIIIA2 VIB2 IV X6Y) and perovskite (CaTiO3) are candidate phases for the immobilisation of rare earth elements (REEs) and actinides (ACTs) in various high level radioactive waste (HLW) forms 1. The effect of radiation damage on the structure and consequently on the durability of these phases is important to predictive modelling of their behaviour in the repository environment and risk assessment.
Date: March 1, 1997
Creator: Smith, K.L.; Zaluzec, N.J. & Lumpkin, G.R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Study of plutonium oxide leak rates from shipping containers. Quarterly progress report, April 1, 1977--June 30, 1977

Description: The study was initiated in October, 1976. Several tasks are to be undertaken in the study. In combination, they have the end objective of defining the leak rates of plutonium oxide powder from characterized leaks. This is the third quarterly report of this work. Previous reports were issued as BNWL-2260-1 and -2. Progress on each of the tasks is reported. (TFD)
Date: July 1, 1977
Creator: Schwendiman, L.S.; Pobereskin, M.; Mishima, J.; Sutter, S.L.; Madia, W.J.; Schmidt, E.W. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Study of plutonium oxide leak rates from shipping containers. Quarterly progress report, October 1, 1977--December 31, 1977

Description: The study was initiated in Oct. 1976. Several tasks are to be undertaken. In combination, they have the end objective of defining the leak rates of plutonium oxide from characterized leaks in shipping containers. Research progress is reported on each of the four tasks. (TFD)
Date: January 1, 1978
Creator: Schwendiman, L.C.; Pobereskin, M.; Mishima, J.; Sutter, S.L.; Madia, W.J.; Schmidt, E.W. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Chemical flowsheet conditions for preparing urania spheres by internal gelation

Description: Small, ceramic urania spheres can be prepared for use as nuclear fuel by internal chemical gelation of uranyl nitrate solution droplets. Decomposition of hexamethylenetetramine (HMTA) dissolved in the uranyl nitrate solution releases ammonia to precipitate hydrated UO/sub 3/. Previously established flowsheet conditions have been improved and modified at ORNL and have been applied to prepare dense UO/sub 2/ spheres with average diameters of 1200, 300, and 30 ..mu..m.
Date: July 1, 1979
Creator: Haas, P.A.; Begovich, J.M.; Ryon, A.D. & Vavruska, J.S.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Quarterly progress report, April 2-June 29, 1979 - Study of plutonium oxide leak rates from shipping containers.

Description: The study was initiated in October 1976. Several tasks are to be undertaken in this study which, when combined, have the end objective of defining the leak rates of plutonium dioxide powder from characterized leaks. Each task is identified and the progress during the reporting period is briefly described.
Date: July 1, 1979
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Subcriticality measurements for two coupled uranyl nitrate solution tanks using /sup 252/Cf-source-driven neutron noise analysis methods

Description: The subcriticality of two interacting solution tanks was determined using /sup 252/Cf-source-driven neutron noise analysis methods. These experiments were the first test of this method for an interacting system with materials (in this case, uranyl nitrate) typical of nuclear materials in processing plants. The experiments were performed to test the conclusions from previous interaction experiments with uranium metal discs for a fissile system with moderation, and to provide data to test theoretical models for coupled systems. The uranium metal experiments showed that the subcritical neutron multiplication factor, k/sub eff/, could be determined using point kinetics without any correction for spatial effects from measurements with the source and detectors located adjacent to the same cylinder, whereas for source-detector configurations with either the source and/or detectors adjacent to different cylinders, a model which incorporates the coupling is required to obtain subcriticality. In the previous experiments with two coupled uranium metal cylinders, the measurements were performed at frequencies (<50 kHz) much lower than the break frequencies (>1 MHz) for the metal discs. Thus, many aspects of the theory relating to the relationships between various spatial models could not be verified in previous experiments. These measurements and their interpretation have shown that (1) point kinetics interpretation of the measured ratios of spectral densities yields the subcritical neutron multiplication factor when the source and detectors are located in or adjacent to one of the cylinders of uranyl nitrate, and (2) the coupling reactivity can be obtained by incorporating a third neutron detector adjacent to the cylinder without the source using the kinetics model of Difilippo, which includes one additional spatial mode in the direction of the coupling.
Date: January 1, 1986
Creator: Mihalczo, J.T.; Blakeman, E.D. & King, W.T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Estimating particle release through gas leaks in dry powder shipping containers

Description: Information is presented from which an estimate can be made of the release of plutonium oxide from shipping containers. The leak diameter is estimated from gas leak tests of the container and an estimate is made of gas leak rate as a function of pressure over the time of interest in the accident. These calculations are limited in accuracy because of assumptions regarding leak geometry and the basic formulations of hydrodynamic flow for the assumed conditions. Sonic flow is assumed to be the limiting gas flow rate. Particles leaking from the air space above the powder will be limited by the low availability of particles due to rapid settling, the very limited driving force (pressure buildup) during the first minute, and the deposition in the leak channel. Equations are given to estimate deposition losses. Leaks of particles occurring below the level of the bulk powder will be limited by mechanical interference when leaks are of dimension smaller than particle sizes present. Some limiting cases can be calculated. When the leak dimension is large compared to the particle sizes present, maximum particle releases can be estimated, but will be very conservative. Further theoretical and experimental studies are needed to better define the hydrodynamics of gas flow in leaks of the size being considered, and to establish particle transport rates through known geometry leak paths.
Date: June 1, 1977
Creator: Schwendiman, L.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Remote micro-encapsulation of curium-gold cermets

Description: A technique is described for fabricating minature, high-density capsules of curium-244 oxide contained in three concentric jackets of metallic gold (or silver), with the outer surface being free of alpha contamination. The completed capsules are right circular cylinders 0.2500-inch diameter and 0.125-inch tall, with each level of containment soldered (or brazed) closed. A typical capsule would contain approx. 70 mg of /sup 244/Cm (5.7 Ci) mixed with 120 mg of gold powder in the form of a cermet wafer clad in three concentric, 0.010-inch thick, liquid tight jackets. This method of fabrication eliminates voids between the jackets and produces a minimum size, maximum density capsule. Cermet densities of 11.5 g/cc were obtained, with an overall density of 17.3 g/cc for the finished capsule.
Date: October 6, 1980
Creator: Coops, M.S.; Voegele, A.L.; Hayes, W.N. & Sisson, D.H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Orbital effects in actinide systems

Description: Actinide magnetism presents a number of important challenges; in particular, the proximity of 5f band to the Fermi energy gives rise to strong interaction with both d and s like conduction electrons, and the extended nature of the 5f electrons means that they can interact with electron orbitals from neighboring atoms. Theory has recently addressed these problems. Often neglected, however, is the overwhelming evidence for large orbital contributions to the magnetic properties of actinides. Some experimental evidence for these effects are presented briefly in this paper. They point, clearly incorrectly, to a very localized picture for the 5f electrons. This dichotomy only enhances the nature of the challenge.
Date: January 1, 1983
Creator: Lander, G.H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Enthalpy and heat capacity of solid UO/sub 2/

Description: Equations have been derived based upon a reevaluation of the enthalpy and heat-capacity data of UO/sub 2/. We recommend a three-term nonlinear equation below 2670 K, with terms representing contributions from phonons, volumetric thermal expansion, and electrons, and a linear equation above 2670 K.
Date: May 1, 1981
Creator: Fink, J.K.; Chasanov, M.G. & Leibowitz, L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Synthesis of crystalline americium hydroxide, Am(OH){sub 3}, and determination of its enthalpy of formation; estimation of the solubility-product constants of actinide(III) hydroxides

Description: This paper reports a new synthesis of pure, microcrystalline Am(OH){sub 3}, its characterization by x-ray powder diffraction and infrared spectroscopy, and the calorimetric determination of its enthalpy of solution in dilute hydrochloric acid. From the enthalpy of solution the enthalpy of formation of Am(OH){sub 3} has been calculated to be {minus}1371.2{plus_minus}7.9 kj{center_dot}mol{sup {minus}1}, which represents the first experimental determination of an enthalpy of formation of any actinide hydroxide. The free energy of formation and solubility product constant of Am(OH){sub 3} (K{sub sp} = 7 {times} 10{sup {minus}31}) have been calculated from our enthalpy of formation and entropy estimates and are compared with literature measurements under near-equilibrium conditions. Since many properties of the tripositive lanthanide and actinide ions (e.g., hydrolysis, complex-ion formation, and thermochemistry) change in a regular manner, these properties can be interpreted systematically in terms of ionic size. This paper compares the thermochemistry of Am(OH){sub 3} with thermochemical studies of lanthanide hydroxides. A combined structural and acid-base model is used to explain the systematic differences in enthalpies of solution between the oxides and hydroxides of the 4f{sup n} and 5f{sup n} subgroups and to predict solubility-product constants for the actinide(III) hydroxides of Pu through Cf.
Date: December 31, 1993
Creator: Morss, L. R. & Williams, C. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

A comparison of long-term retention of plutonium oxide in lung based on excretion data with observed lung burdens at autopsy

Description: Experience in the nuclear industry has shown that the most frequent route for significant plutonium deposition in man is by inhalation. After an accidental inhalation exposure to plutonium oxide has occurred, an attempt is usually made to determine the lung burden using in-vivo measurement techniques. However, this will not be possible if the amount deposited is less than the detection capability of the counter. Likewise, it may not be possible for even larger intakes if they are first discovered as a results of a routine examination after much of the plutonium has transferred out of the lungs. Under these conditions, the initial lung burden and dose assessment may, of necessity, be based entirely on excretion date. This paper discusses three plutonium inhalation cases for which autopsy data are available to demonstrate the difficulties and uncertainties of such assessments and to emphasize the need for enhanced routine surveillance of the worker and work place to assure that intakes are detected at the time they occur. An in-depth review of the findings for these three cases suggests that the use of urine excretion data applied to ICRP lung model assumption will result in large uncertainties in estimates of the pulmonary burden and lung dose. These estimates will be improved if the material inhaled can be better characterized and by using clearance half times developed for the individual rather than the default values for Class Y material recommended by the ICRP.
Date: May 1, 1985
Creator: Heid, K.R.; Jech, J.J.; Kathren, R.L. & Sula, M.J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Thermodynamics and sublimation chemistry of plutonium - oxygen - chlorine

Description: Pyrochemical processing of plutonium produces spent salts that contain plutonium bearing species. One of the species is PuOCl. The behavior of pure PuOCl at high temperatures and PuOCl in the liquid salt matrix is not well characterized. The purpose of the study is to establish the vapor pressure and vapor composition for the sublimation of PuOCl. The results of the sublimation study and the thermodynamic properties associated with the sublimation process are presented.
Date: July 1, 1993
Creator: Williamson, M. A. & Kleinschmidt, P. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Investigation of the radiological safety concerns and medical history of the late Joseph T. Harding, former employee of the Paducah Gaseous Diffusion Plant

Description: An ex-employee's claims that inadequate enforcement of radiation safety regulations allowed excess radiation exposure thereby causing his deteriorating health was not substantiated by a thorough investigation.
Date: March 1, 1981
Creator: Vallario, E.J. & Wolfe, H.R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Equilibria and thermodynamic properties of the plutonium-hydrogen system

Description: Equilibrium, kinetic and x ray diffraction data show the existence of two stability regimes in the Pu-H system. A metastable solid solution between CaF/sub 2/-type PuH/sub 1/ /sub 9/ and anti-Fe/sub 3/Al-type PuH/sub 3/ /sub 0/ forms at low temperature and behaves as an ideal solid solution. Equilibrium and calorimetric results show that the enthalpy of formation varies linearly from -38 to -50 kcal/mol between the lower phase boundary and the trihydride. The phase relationships established at high temperature are similar to those of the lanthanide difluoride-lanthanide trifluoride systems. A series of CaF/sub 2/-related phases apparently forms between PuH/sub 1/ /sub 9/ and PuH/sub 2/ /sub 5/; a nonstoichiometric hexagonal (LaF/sub 3/-type) hydride exists in the range PuH/sub 2/ /sub 9/-PuH/sub 3/ /sub 0/. A procedure for preparing pure hexagonal puH/sub 3/ /sub 00/ is described, and the hysteresis behavior of the Pu-H system is discussed.
Date: January 1, 1980
Creator: Haschke, J.M.; Hodges, A.E. III; Smith, C.M. & Oetting, F.L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Decomposition kinetics of plutonium hydride

Description: Kinetic data for decomposition of PuH/sub 1/ /sub 95/ provides insight into a possible mechanism for the hydriding and dehydriding reactions of plutonium. The fact that the rate of the hydriding reaction, K/sub H/, is proportional to P/sup 1/2/ and the rate of the dehydriding process, K/sub D/, is inversely proportional to P/sup 1/2/ suggests that the forward and reverse reactions proceed by opposite paths of the same mechanism. The P/sup 1/2/ dependence of hydrogen solubility in metals is characteristic of the dissociative absorption of hydrogen; i.e., the reactive species is atomic hydrogen. It is reasonable to assume that the rates of the forward and reverse reactions are controlled by the surface concentration of atomic hydrogen, (H/sub s/), that K/sub H/ = c'(H/sub s/), and that K/sub D/ = c/(H/sub s/), where c' and c are proportionality constants. For this surface model, the pressure dependence of K/sub D/ is related to (H/sub s/) by the reaction (H/sub s/) reversible 1/2H/sub 2/(g) and by its equilibrium constant K/sub e/ = (H/sub 2/)/sup 1/2//(H/sub s/). In the pressure range of ideal gas behavior, (H/sub s/) = K/sub e//sup -1/(RT)/sup -1/2/ and the decomposition rate is given by K/sub D/ = cK/sub e/(RT)/sup -1/2/P/sup 1/2/. For an analogous treatment of the hydriding process with this model, it can be readily shown that K/sub H/ = c'K/sub e//sup -1/(RT)/sup -1/2/P/sup 1/2/. The inverse pressure dependence and direct temperature dependence of the decomposition rate are correctly predicted by this mechanism which is most consistent with the observed behavior of the Pu--H system.
Date: January 1, 1979
Creator: Haschke, J.M. & Stakebake, J.L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department