bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bulk Solubility and Speciation of Plutonium(VI) in Phosphate-Containing Solutions
Authors: Weger H. T. , Okajima S. , Cunnane J. C. , Reed D.T 
Published: March 2011

ABSTRACTThe solubility and speciation of Pu(VI) with phosphate is being investigated to determine the ability of phosphate to act as an actinide getter. In the initial studies performed, solubility was approached from oversaturation at an initial pH = 4, 10 and 13.4. Absorption spectra were recorded, the solution filtered, and the filtrate analyzed for Pu content. Absorption spectra were obtained at varying phosphate concentrations, and at pH of 2.7 to 11.9. The effect of complexation on the 833 nm Pu(VI) band was characterized. Evidence for three phosphate complexes was obtained for pH < 10, which have absorption bands at 842, 846 and 849 nm. Evidence for colloid formation was observed, but is not conclusive. The possible presence of colloids prevented an accurate determination of true solubility. A concentration of 10−5 to 10−6M Pu(VI) was measured in solutions at pH ≤ 10 that was filtered with a 50 nm filter. Pu(VI)-phosphate complexes predominated at pH ≤ 11.6. At higher pH, however, only hydrolyzed Pu(VI) was detected. At pH = 12, the concentration of Pu(VI) was as high as 10−4M.
Evidence of Radiolytic Oxidation of 241Am in Na+ / Cl− / HCO−3/ CO2−3 Media.
Authors: Giffaut Eric , Vitorge Pierre 
Published: March 2011

ABSTRACTThis paper examines Americium behaviour in CI− media at room temperature in connection with environmental and waste disposal programs. Most published values on U, Np, Pu and Am complexation in chloride media have been determined using extraction methods. Spectrophotometric techniques are not sensitive enough to prove actinide complexation by chloride, which is confirmed in this paper for Am(III).Am(OH)3(s), AmOHCO3(s), Am2(CO3)3(s) or NaAm(CO3)2(s) solid phases can control the Am solubility, depending on the chemical conditions of the aqueous phase (usually PCO2). 241Am solubility is here found to be higher in NaCl 4M media than in NaCl 0.1 M (up to 3 orders of magnitude). Addition of a reducing agent (metallic iron) lowers the solubility. After a week, solubilities in NaCl 0.1 M and 4 M are similar. These results are consistent with Am(III) radiolytic oxidation to Am(V), due to cc radiations. Little evidence of Cl− or mixed Cl−-CO2−3 complexes is found in these conditions. In Na+-OH−-Cl− media, 241Am(III) oxidation had also been proposed. Slow kinetics of precipitation could induce experimental uncertainities.
Microbial Effects on the Radionuclide Transport in a Deep Nuclear Waste Repository
Authors: Spor Herve , Trescinski M. , Libert M.F. 
Published: March 2011

ABSTRACTThis study deals with the effects of microorganisms on the transport of radionuclides under deep nuclear-waste disposal conditions. Metabolism of a cellulolytic microorganism is studied. Cellulose, as a carbon source, is representative of nuclear waste.A pilot device allows the study of the general effect of microrganisms. Bioleaching of radionuclides by a fungal culture is performed on columns of clay and cement used as engineered barriers. Cesium and Uranium had been incorporated into matrices prior to the tests. Operating conditions have been choosen according to realistic conditions of a deep repository. The production of organic acids by microorganisms is qualitatively and quantitatively determined.In addition, direct effects of microorganisms (biosorption, bioaccumulation) and indirect effects (complexing agents issued from the diodegradation of cellulose) on the transport and/or retardation of radionuclides are studied.
Initial Demonstration of the Vitrification of High-Level Nuclear Waste Sludge Containing an Organic Cs-Loaded Ion-Exchange Resin
Authors: Bibler N. E. , Bibler J. P. , Andrews M. K. , Jantzen C. M. 
Published: March 2011

ABSTRACTWhen immobilizing into borosilicate glass the radionuclides in the caustic high-level radioactive wastes stored in the USA, the soluble fission product Cs-137 has to be removed from supernates of the wastes. In the current processes zeolites or an organic precipitant will be used to remove the Cs. These are then treated further and mixed with the radioactive sludges and vitrified into a borosilicate glass. This paper describes the vitrification of a mixture resulting from using a new process to remove Cs from the caustic supernate. A resorcinol based organic ion exchange resin is used. This resin was then mixed with sludge and frit and vitrified. Using an organic ion exchange resin rather than zeolite or the organic precipitant has certain advantages. For example, use of the zeolite increases the amount of glass to be made and use of the organic precipitant produces benzene as a secondary waste stream. Results in the paper indicate that a mixture of the resin, sludge and frit can be successfully vitrified in a joule-heated, slurry fed melter. However, when resin is present in the feed, the glass becomes less durable due to the increased amount of Fe(II) caused by reduction of Fe(III) in the melt. Based on the durabilities of other waste glasses, this glass is still suitable as a canistered wasteform.
Radio-Labelled Humic Materials in Migration Studies
Authors: Carlsen Lars , Lassen Pia , Warwick Peter , Randall Amanda 
Published: March 2011

ABSTRACTHumic- and fulvic acids are able to complex polyvalent metal ions, e.g. radionuclides, leading to soluble complexes of significant strength, thereby decreasing the sorption of these compounds to soils and sediments. The interaction of humic materials with radionuclides may significantly influence the availability and transport of the latter in the environment. Typically, studies along these lines have focussed almost exclusively on the radionuclides, whereas the actual role of the humic material has been elucidated only indirectly. In order directly to study the behaviour of the naturally occurring organic macro-molecules in relation to the environmental fate of radionuclides, radio-labelled humic- and fulvic acids can advantageously be applied. Radio-labels such as 14C and 125I have successfully been covalently incorporated in humic- and fulvic acids. Labelling of humic substances as well as preliminary migration studies are discussed
Development of a Gas Method for Migration Studies in Fractured and Porous Media.
Authors: VÄÄtÄinen Kusti , Timonen Jussi , HautojÄrvi Aimo 
Published: March 2011

ABSTRACTA gas method for fast measurements of diffusion properties of porous materials has been developed. Diffusion coefficients in the gas phase are typically four orders of magnitude larger than those in the liquid phase. For samples whose structures do not change much upon drying it is possible to estimate the diffpision properties of the liquid phase when the properties of the gas phase are known. Advantages of the gas method are quick and easy measurements and therefore they can be used to optimize the liquid-phase measurements which may last months or years. For materials with good correlation between the gas and liquid-phase diffusion, the number of liquid phase measurements can be greatly reduced.Nitrogen was used as the carrier gas and helium as the tracer gas. Helium concentrations were measured by using standard techniques. The equipment was tested for two sample geometries, a column made of a polished granite slab and an acrylic slab with a flow channel in between, and a hollow bore core where diffusion occurs through the sample. Both types of measurement were modelled and apparent diffusion coefficients in the gas phase were determined.
Effects of Some Common Geological Features on Two-Dimensional Variably Saturated Flow
Authors: Bagtzoglou Amvrossios C. , Ababou Rachid , Sagar Budhi , Islam M. Rashidul 
Published: March 2011

ABSTRACTThis paper presents results of unsaturated flow simulations undertaken as an auxiliary analysis for the Iterative Performance Assessment (IPA) project, one of the approaches adopted' by the U.S. NRC to develop repository license application review capabilities. The effects on flow of common geological features, such as nonhorizontal stratification and vertical or near-vertical fault zones intersecting the strata, in a two-dimensional (2D) domain are studied. Results indicate that the presence of layers and crosscutting fault zones tend to induce three-dimensional (3D) unstable flows in the unsaturated zone. The instability is manifested in our simulations by an oscillatory behavior of steady state. This numerical instability imposes extremely stringent criteria on the time step used in the simulation. Finally, once stable steady-state solutions are attained, the effect of the crossing point in the matrix-fault unsaturated hydraulic conductivity curve on groundwater flux vectors and moisture content distributions is studied.
Leach Resistance Properties and Release Processes for Salt-Occluded Zeolite A
Authors: Lewis M. A. , Fischer D. F. , Laidler J. J. 
Published: March 2011

ABSTRACTThe pyrometallurgical processing of spent fuel from the Integral Fast Reactor (IFR) results in a waste of LiCI-KCI-NaCI salt containing approximately 10 wt% fission products, primarily CsCI and SrCI2. For disposal, this waste must be immobilized in a form that it is leach resistant. A salt-occluded zeolite has been identified as a potential waste form for the salt. Its leach resistance properties were investigated using powdered samples. The results were that strontium was not released and cesium had a low release, 0.056 g/m2 for the 56 day leach test. The initial release (within 7 days) of alkali metal cations was rapid and subsequent releases were much smaller. The releases of aluminum and silicon were 0.036 and 0.028 g/m2, respectively, and were constant. Neither alkali metal cation hydrolysis nor exchange between cations in the leachate and those in the zeolite was significant. Only sodium release followed t0.5 kinetics. Selected dissolution of the occluded salt was the primary release process. These results confirm that salt-occluded zeolite has promise as the waste form for IFR pyroprocess salt.
Interpreting Drop-Weight Impact Results in Terms of Deformation Dependent Initiation Criteria
Authors: Baker P. J. , Mellor A. M. 
Published: March 2011

AbstractThe impact sensitivity of energetic materials is frequently measured in small-scale drop-weight tests. Plastic deformation of the sample leads to heating, the onset of chemical reaction, and eventual ignition. An analytic model provides deformation dependent estimates of the energy delivered to the sample, its stress state, and its temperature distribution. Results for hydoxy-terminated polybutadiene (HTPB/AP) propellants are interpreted in terms of two initiation criteria: critical decomposition temperature and critical thickness for shear banding. The influence of friction, impact velocity, and sample size on initiation give possible explanations of experimental results. Sample material properties variations are studied for both initiation criteria. The model includes energy localization by varying the thickness of shear layers at the sample/machine interface.
Ab Initio Study of Electronic Structure of RDX Molecular Crystal
Authors: Gao Guang , Pandey Ravindra , Kunz A. Barry 
Published: March 2011

AbstractAn embedded molecular cluster model is used to study the electronic structure of cyclotrimethylene trinitramine(RDX) molecular crystal. In this model, a molecular cluster describing a local region of the crystal is treated in the Hartree-Fock approximation. The embedding lattice is represented by multipoles that are determined quantum-mechanically. Cluster-lattice orthogonality is achieved by transforming canonical orbitals to orbitals which are localized on individual molecular sites by means of a self-consistent localization potential. Results for the free molecule and the perfect crystal demonstrate the domination of three N-NO2 groups on intermolecular properties. For the defective crystal, results show a significant distortion in the electronic structure caused by local deformations in the lattice that may account for the formation of hot spots.
Electronic Excitations Preceding Shock Initiation in Explosives
Authors: Sharma J. , Beard B. C. 
Published: March 2011

AbstractElectronic excitations which precede and can facilitate chemical reactivity of explosive molecules during shock passage will be discussed. The structurally similar family of explosives, TATB, DATB, Picramide and TNB were the focus of this work. It has been found that the energy of shake-up transitions observed in x-ray photoelectron spectra of these molecules shows a linear relation with the explosive sensitivity. To the contrary, optical absorption maxima, dependant upon dipole selection rules display a trend opposite that intuitively expected in relation to ease of initiation. The shake-up transitions are governed by monopole selection rules, so that the transitions between initial and final states of the same symmetry are allowed. The forbiddeness of the excited state may favor proton transfer, bond breakage and free radical formation relative to de-excitation by returning to the ground state. Electronic excitations of this type are believed to be important to multiphonon up pumping. The Is core hole resulting from photoionization creates a central coulomb force that shrinks the orbitals, simulating conditions similar to those of high pressure or shock passage. These factors may be at the heart of the correlation between the shake-up promotion energy and explosive sensitivity.
Atomic Force Microscopy of Ammonium Perchlorate
Authors: Yoo Minsun , Yoon Seokwon , Lozanne Alex De 
Published: March 2011

AbstractWe have studied the (210) surface of ammonium perchlorate (NH4ClO4) with an atomic force microscope (AFM) in air. Large scale images show monomoreculat steps that are often aligned with major crystalline directions. Surface modification is clearly observed with forces as low as 30 nN, but is usually limited to the bottom and the sides of the field of view, where the tip scans for a long time and where it turns around, respectively. At the molecular scale we have observed structures with substantial order, with minimum lateral sizes of 3 Å. The identification of these features is difficult due to the large unit cell of this compound (40 atoms per unit cell), and the lack of perfect order in the images. We use the SARCH/LATUSE progrmn developed by Van Hove and Hermann to analyze this structure. Ammonium perchlorate is hygroscopic; it is therefore possible that surface modification is enhanced by the moisture present in air. Experiments in a dry atmosphere have confirmed this explanation. We have therefore designed and built a UHV (ultra-high vacuum) AFM for these studies. The first images from this instrument are presented here.
Energetic Crystal-Lattice-Dependent Responses
Authors: Armstrong R. W. , Ammon H. L. , Du Z. Y. , Elban W. L. , Zhang X. J. 
Published: March 2011

AbstractThe occurrence of [100] direction slip on the (021) slip plane of orthorhombic RDX (cyclotrimethylenetrinitramine, (CH2·N·NO2]3) is shown to favor the formation of 1,3-dinitroso-5-nitro-l,3,5-triazacyclohexane, as detected in drop-weight impact tests at sensitivity height levels near to those measured for initiation. Also, the reported observation of deformation twinning in the chemically-related monoclinic HMX (cyclotetra-methylenetetranitramine, (CH2·N·NO2 ]4) crystal lattice is explained on the basis of the greater flexibility of the larger HMX molecule allowing a number of bond rotations that are required to produce a relatively unusual Type II deformation twinning structure. These examples give support to the consideration that on the molecular level involved in deformation-induced decompositions there may be a direct mechanical force aspect that is additional to the established importance of “hot spot” heating, say, as described for dislocation pile-up avalanches in RDX.
Molecular Composition, Structure, and Sensitivity of Explosives
Authors: Storm Carlyle B. , Travis James R. 
Published: March 2011

AbstractHigh explosives, blasting agents, propellants, and pyrotechnics are all metastable relative to reaction products and are termed energetic materials. They are thermodynamically unstable but the kinetics of decomposition at ambient conditions are sufficiently slow that they can be handled safely under controlled conditions. The ease with which an energetic material can be caused to undergo a violent reaction or detonation is called its sensitivity. Sensitivity tests for energetic materials are aimed at defining the response of the material to a specific situation, usually prompt shock initiation or a delayed reaction in an accident. The observed response is always due to a combination of the physical state and the molecular structure of the material. Modeling of any initiation process must consider both factors. The physical state of the material determines how and where the energy is deposited in the material. The molecular structure in the solid state determines the mechanism of decomposition of the material and the rate of energy release. Slower inherent reaction chemistry leads to longer reaction zones in detonation and inherently safer materials. Slower chemistry also requires hot spots involved in initiation to be hotter and to survive for longer periods of time. High thermal conductivity also leads to quenching of small hot spots and makes a material more difficult to initiate. Early endothermic decomposition chemistry also delays initiation by delaying heat release to support hot spot growth. The growth to violent reaction or detonation also depends on the nature of the early reaction products. If chemical intermediates are produced that drive further accelerating autocatalytic decomposition the initiation will grow rapidly to a violent reaction.
Surface Chemistry of Energetic Materials at High Temperature
Authors: Brill Thomas B. 
Published: March 2011

AbstractThe chemistry at the surface of a burning propellant plays a major role in the burnrate, the stability of the flame, and the potential for a run-away hazardous event. Chemical details can be determined experimentally by simulating the burning surface with a thin film of material heated rapidly to the surface temperature. T-Jump/FTIR spectroscopy is designed to create these conditions. The dominant, initial, heat-producing reactions in the surface zone of NH4ClO4, NH4NO3, NH4[N(NO2)2], HMX, RDX, and DNNC are elucidated at high temperatures representative of the burning surface.
Correlation Time for Polymer Chain Motion Near the Glass Transition in Nitrocellulose.
Authors: Jayakody J. R. P. , Bulusu S. , Marino R. A. 
Published: March 2011

AbstractThe NMR chemical shift anisotropy (CSA) has a temperature dependence as a result of thermal motions of the NMR site. For slow motions of a polymer chain at or near the glass transition, Tg, the CSA begins to decrease, with the characteristic powder pattern features, shoulders and divergence, approaching one another. This motional narrowing can be interpreted to yield the correlation time of the thermal motions. If Δ is the rigid-lattice shoulder to shoulder chemical shift anisotropy and τ is the correlation time of the slowmotion of the polymer chains, the total fractional shift, δ/Δ, for the general asymmetric case is found to bederived using Lee's theory. In this work, Nitrocellulose isotopically highly enriched with 15N was studied at four temperatures between 27° and 120° Celsius. To circumvent signal-to-noise problems in obtaining CSA data from a polycrystalline/amorphous sample, we used the Magic Angle Spinning (MAS) technique of Herzfeld and Berger. The principal values of the chemical shift tensor were then obtained from the relative intensities of the spinning sidebands in the MAS NMR spectrum. Correlation times were found to be of the order of 400 ms at 70°C, and 17 ms at 120°C.
Laser-Based Sensitive Detection of Energetic Materials
Authors: Lemire G. W. , Simeonsson J. B. , Sausa R. C. 
Published: March 2011

AbstractThe development of a novel technique for sensing trace vapors of -NO2 containing compounds is reported. This technique is based on the use of one laser operating at 226 nm to both photofragment the target molecule and detect the characteristic NO fragment, formed from a rapid predissociation of NO2, by resonance-enhanced multiphoton ionization (REMPI) via its A2Σ+ - X2Π (0,0) band origin. The analytical utility of this technique is demonstrated on a number of compounds, including dimethylnitramine, nitromethane, nitrobenzene, TNT, and RDX, employing molecular beam sampling with time-of-flight mass spectrometric analysis of the jet cooled analyte seeded in an atmosphere of buffer gas. For RDX and TNT, a detection limit of 8 and 24 ppb, respectively, is demonstrated using a laser energy of 100 microjoules/pulse.
Nitrogen Radicals from Thermal and Photochemical Decomposition of Ammonium Perchlorate, Ammonium Dinitramide, and Cyclic Nitramines
Authors: Pace M. D. 
Published: March 2011

AbstractFree-radical thermal and photochemical decomposition products of ammonium dinitramide (ADN), an acyclic nitramine, are compared to that of cyclic nitramines (RDX, HMX, and HNIW) and to ammonium perchlorate (AP). Photochemical formation of NO2 from uvphotolysis of ADN at 77 K is found to follow first-order kinetics; whereas, zero-order NO2 formation is observed from the cyclic nitramines under the conditions of this experiment. Mechanisms are suggested for ADN decomposition. A general trend of cyclic nitramines to thermally decompose forming nitroxide radicals is supported by 15N-ring-labeled HNIW results. ADN thermally decomposes at 19° C to form free-radical reaction products in solution with tetrahydrothiophene-1,1-dioxide.
The Importance of Sterically Hindered Shear in Determining the Sensitivity of Explosive Crystals
Authors: Dick Jerry J. 
Published: March 2011

AbstractSterically hindered shear in a plane shock wave in an explosive crystal is shown to be important in determining the shock sensitivity of pentaerythritol tetranitrate and nitromethane. The steric hindrance is analyzed at the intermolecular level in the unit cell, and compared to the experimental evidence.
Fracture Surface Topography of Octol Explosives
Authors: Lanzerotfi M. Yvonne D. , Pinto James J. , Wolfe Allan 
Published: March 2011

AbstractEnergetic materials are of significant interest for scientific and practical reasons in the extraction (mining) industry, space propulsion, and ordnance. The nature of the fracture process of such materials under high acceleration is of particular interest, especially in ordnance. This paper describes new experimental and analysis techniques that allow us to characterize quantitatively and to compare the fracture surfaces of different energetic materials, and to deduce the specific fracture mechanisms. The techniques are widely applicable to other composite systems. In the materials discussed herein, topographical profiles spaced 1.0 mm apart across the fracture surfaces of two types of Octol have been obtained with a diamond stylus profilometer. Spatial power spectra (wavelengths of 1.0 μm 1.0 cm) have been calculated using a prolate spheroidal data window in the horizontal space domain prior to using a fast Fourier transform algorithm. The spatial power density of the fracture surface profiles is found in general to decrease with increasing spatial frequency over the region of interest, ≈ 1 mm-1 to ≈ 1 cm-1. Quasi-periodic peaks corresponding to HMX particle sizes are observed in the Octol spatial power spectra. These peaks indicate the inhomogeneous HMX grain size distribution in the Octol fracture surfaces. Peaks in the Octol spectra indicate that intergranular fracture often occurs between the TNT and HMX grains. Fractal analysis of the Octol power spectral slopes indicates the regions of deterministic, intergranular failure and the regions of the nondeterministic, trans-granular failure through TNT or HMX grains. This non-deterministic (fractal) failure is chaotic and may indicate the origin of failure in the sample.