bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Justification for the Use of Data from Accelerated Leach Tests of Glass
Authors: Ahn Tae M. , Interrante Charles G. , Weller Richard A. 
Published: March 2011

ABSTRACTA case is made for the use of short-term laboratory data in making predictions on the likelihood of significant colloid formation in supersaturated leachates of glass, under long-term repository conditions, using “accelerated tests” with a large ratio of the surface area of the glass to the leachate volume. In the repository conditions in which colloids can form, long-term leaching may be a kinetically-controlled process that involves the continuous formation of colloids. If this kinetic process dominates, it could lead to a significant increase in the predicted rates of radionuclide release. The question is whether or not colloids may form after prolonged times; the delayed formation would make it difficult to use short-term laboratory test results to represent (or predict) the long-term and cumulative effects of radionuclides. In this work, the pertinent long-term kinetic processes are identified in part. Classical nucleation theory for particle formation, as a potential condensation mechanism for colloid formation, is applied to explain pertinent experimental data on colloid formation. The classical theory, which is justified for this discussion, indicates that as supersaturation of a leachate is decreased, the nucleation rate decreases most significantly, while the incubation time increases at a small rate. As a result of this decreased nucleation rate, the significance of colloids tends to vanish, and usefulness of data from “accelerated“ laboratory tests may be applicable to long-term behavior.
Long-Term Predictions Relating to Environment Sensitive Cracking.
Authors: Parkins R. N. 
Published: March 2011

ABSTRACTConsideration is given to the environmental requirements of environment sensitive cracking (ESC) of ferritic steels, involving hydrogen-induced or dissolution-related mechanisms of cracking. Pitting, with associated local pH changes, may result in hydrogeninduced cracking of simple ferritic steels, as has been observed with high pressure gas pipelines in contact with ground waters, and may constitute a greater potential failure mechanism for waste containers than dissolution-related cracking with its requirement of relatively concentrated solutions. However, the stochastic nature of pit initiation, together with the distributions of crack nucleation and growth rates, suggest that a probabilistic, as opposed to a purely deterministic, approach will need to be applied to life prediction estimates for waste containers.
Experiments and Modelling Studies Concerning Localised Corrosion of Carbon Steel and Stainless Steel Containers for Intermediate- and Low-Level Radioactive Waste
Authors: Hoch A.R. , Naish C.C. , Sharland S.M. , Smith A.C. , Taylor K.J. 
Published: March 2011

ABSTRACTCurrent plans for disposal of low- and intermediate-level radioactive wastes (LLW and ILW) in the UK include enclosing much of the waste in carbon steel or stainless steel containers. Modelling and experimental studies that aim to characterise the period and extent of the localised corrosion in these containers are described. The period, during which localised corrosion can be initiated and sustained in the post-closure phase of the repository is estimated. The likely modes of localised corrosion are identified, based on further consideration of the environmental conditions to which the metals are exposed. Detailed research in progress includes investigation of the rate of pitting corrosion for carbon steel, and the possible occurrence of crevice corrosion of stainless steel.
Thermodynamic Modelling of the Effect of Hydroxycarboxylic Acids on the Solubility of Plutonium at High pH
Authors: Moreton Anthony D 
Published: March 2011

ABSTRACTA number of the hydroxycarboxylic acids generated by the alkaline degradation of cellulosic wastes under reducing conditions in a cementitious repository can significantly increase the solubility of the actinides at high pH, especially plutonium. The solubility of plutonium at pH 12, in the presence of a range of hydroxycarboxylic acids containing a number of hydroxyl groups and between one and three carboxylate groups, has been modelled using the HARPHRQ code. All the plutonium-organic complexes assumed in the model are based on a stable unit in which a central plutonium ion is bound by four oxygen atoms. The oxygen atoms can be provided either by a deprotonated hydroxyl group on one of the ligands, or by hydroxide ions.
A Comparative Study of Europium, Thorium and Uranium Binding to an Aquatic Fulvic Acid
Authors: NordÉn M. , Albinsson Y. , Ephraim J.H. , Allard B. 
Published: March 2011

ABSTRACTAdvances in safe management and disposal of radioactive waste have shown that a comprehensive program requires the incorporation of dissolved organics into radwaste and transport effluent models, with respect to their binding of radionuclides. The binding of Eu3+, Th4+and UO22+to a well-characterized aquatic fulvic acid has been studied using an ultrafiltration method at a bulk electrolyte concentration of 0.10 M NaClO4, trace amounts of radionuclides and fulvic acid concentrations of 60 and 120 mg/l. The results expressed as the overall complex formation function, βov, versus pH show the following order: Th4+> Eu3+> UO22+. The estimated βov, values have been discussed by considering the aqueous chemistry of Eu3+, Th4+and UO22+vis-à-vis the solution chemistry of the fulvic acid sample.
The Role of Siderophores in the Transport of Radionuclides
Authors: Hersman Larry E. , Palmer Philip D. , Hobart David E. 
Published: March 2011

ABSTRACTIron exists in aerobic soil and water environments most commonly as insoluble Fe(III). Siderophores are powerful, microbially produced chelating agents that are used to mobilize the insoluble Fe(III) cation. Over 80 siderophores have been isolated and characterized, with some reportedly having iron-binding constants as high as 1052. Fe(III) and Pu(IV) are similar in their charge/ionic radius ratio (4.6 and 4.2, respectively); therefore, Pu(IV) may serve as analog to Fe(III). It is possible that some radioactive wastes could be chelated by naturally occurring siderophores, thereby altering the transport rates of those elements through the subsurface environment. This investigation wn 9 initiated to investigate that possibility. The binding of239Pu(IV) by four chelating agents is reported in this paper: a siderophore isolated and purified from aPseudomonassp.; desferal, a ferrioxamine siderophore commonly used for deferration therapy; EDTA, ethylenediaminetetraacetic acid; and, citrate, trisodium salt.
Colloid Properties in Granitic Groundwater Systems, with Emphasis on the Impact on Safety Assessment of a Radioactive Waste Repository
Authors: Degueldre C. 
Published: March 2011

ABSTRACTSince colloids are present in all groundwaters, they are studied because of their potential role in the migration of relevant radionuclides in the geosphere. Colloid sampling and characterization campaigns have been carried out in the Grimsel area, Switzerland (Transitgas tunnel, Grimsel Test Site) and in the North Switzerland/Black Forest area (Menzenschwand, Bad Sickingen, Zurzach, Leuggem). On the basis of results obtained for 25 groundwaters a consistent picture is emerging. Colloids in granitic systems are basically composed of components of the aquifer materials (clay, silica). Under the hydrogeochemical conditions existing at depth in crystalline rock systems, colloid concentrations are not expected to exceed 100 ppb. However, under transient conditions when physical and/or chemical changes are occuring (e.g., hydrothermal activity), colloid generation may be enhanced. Colloid concentration of 10 ppm may be observed when the calcium concentration is low enough (<5 ppm).Whereas reversible sorption on the host rock leads to conservative predictions for radionuclide migration rates, the reverse is true for sorption onto colloids. The most conservative assumptions are therefore reversible nuclide sorption and colloid attachment on the rock and irreversible sorption on colloids.For calcium concentrations larger than 5 ppm, and sorption capacities at the nM level, their presence in granitic aquifer can be neglected in safety analyses when reversible sorption onto colloids is considered. This situation could change when sorption is followed by aggregation or incrustation processes. This study shows that for the colloid conservative size distributions found and for the granitic water conducting fissures considered, sorption-agglomeration reactions are unlikely to take place. Therefore, irreversible sorption by this mecanism is improbable.
Is it Possible to Demonstrate Compliance with the Regulations for High-Level-Waste Repositories?
Authors: Bingham Felton W. 
Published: March 2011

ABSTRACTThe regulations that currently govern repositories for spent fuel and high-level waste require demonstrations that are sometimes described as impossible to make. To make them will require an understanding of the current and the future phenomena at repository sites; it will also require credible estimates of the probabilities that the phenomena will occur in the distant future. Experts in many fields—earth sciences, statistics, numerical modeling, and the law—have questioned whether any amount of data collection can allow modelers to meet these requirements with enough confidence to satisfy the regulators. In recent years some performance assessments have begun to shed light on this question because they use results of actual site investigations. Although these studies do not settle the question definitively, a review of a recent totalsystem assessment suggests that compliance may be possible to demonstrate. The review also suggests, however, that the demonstration can be only at the “reasonable” levels of assurance mentioned, but not defined, in the regulations.
Iterative Performance Assessment for the Greater Confinement Disposal Facilities: Preliminary Results of Round Two
Authors: Olague Natalie E. , Baer T.A. , Conrad S.H. 
Published: March 2011

ABSTRACTThe Department of Energy's Nevada Operations Office has disposed of a small quantity of transuranic waste at the Greater Confinement Disposal (GCD) facility in Area 5 of the Nevada Test Site. The Environmental Protection Agency standards for disposal of transuranic waste (40 CFR 191) require that a performance assessment be conducted and an iterative approach has been adopted. This approach consists of using performance assessment results to guide the collection of site characterization data, and in turn, new site characterization data is incorporated into each successive iteration of the performance assessment. The results of the first iteration indicated that the GCD site should be able to comply with 40 CFR 191. This paper presents results of the second iteration based on results from site-specific environmental tracer studies. These studies indicate significantly lower recharge values then those used in the first performance assessment iteration. For performance assessment these results imply that the downward ground-water advection pathway may be negligible, and therefore, the upward liquid diffusion pathway becomes more significant. The models and the model parameters that were used to simulate this upward pathway have been refined. The preliminary results from these models still indicate that the GCD facility should be able to comply with the Containment Requirements in 40 CFR 191.
The Use of Formal and Informal Expert Judgments When Interpreting Data for Performance Assessments
Authors: Rechard Rob P. , Trauth Kathleen M. , Rath Jonathan S. , Guzowski Robert V. , Hora Stephen C. , Tierney Martin S. 
Published: March 2011

ABSTRACTThis paper discusses the general process by which data and information are compiled and used for defining modeling parameters. These modeling parameters are input for the mathematical models that are used in performance assessments of the Waste Isolation Pilot Plant (WIPP), near Carlsbad, NM, which is designed to safely manage, store, and dispose of transuranic radioactive wastes. The physical and temporal scales, and the difficulty of obtaining measurements in geologic media make interpretation of measured data, including the difference between laboratory experiment scale and repository scale, important tasks. In most instances, standard scientific practices can ensure consistency of data use. To illustrate this point, an example is provided of the interpretation of field measurements of intrinsic permeability for use in computational models using the bootstrap technique. In some cases, sufficient information can never be collected, interpretation of the information is controversial, or information from diverse disciplines must be used. A procedure that formalizes the standard scientific practices under these conditions has been developed. An example is provided of how this procedure has been applied in eliciting expert judgments on markers to deter inadvertant human intrusion into the WIPP.
Molecular Dynamics Simulations of Shock-Defect Interactions in Two-Dimensional Nonreactive Crystals
Authors: Sinkovits Robert S. , Phillips Lee , Oran Elaine S. , Boris Jay P. 
Published: March 2011

AbstractThe interactions of shocks with defects in two-dimensional square and hexagonal lattices of particles interacting through Lennard-Jones potentials are studied using molecular dynamics. In perfect lattices at zero temperature, shocks directed along one of the principal axes propagate through the crystal causing no permanent disruption. Vacancies, interstitials, and to a lesser degree, massive defects are all effective at converting directed shock motion into thermalized two-dimensional motion. Measures of lattice disruption quantitatively describe the effects of the different defects. The square lattice is unstable at nonzero temperatures, as shown by its tendency upon impact to reorganize into the lower-energy hexagonal state. This transition also occurs in the disordered region associated with the shock-defect interaction. The hexagonal lattice can be made arbitrarily stable even for shock-vacancy interactions through appropriate choice of potential parameters. In reactive crystals, these defect sites may be responsible for the onset of detonation. All calculations are performed using a program optimized for the massively parallel Connection Machine.
Delayed Initiation in a Model Energetic Material
Authors: Robertson D. H. , Brenner D. W. , White C. T. 
Published: March 2011

AbstractWe present a simulation studying the initiation of a model energetic molecular solid. For low-velocity, massive flyer-plate impact, the model detonation initiates behind a compaction shock. This detonation front subsequently overtakes the compaction shock exhibiting a behavior qualitatively similar to that observed in experminental studies of homogeneous initiation and delayed detonation from low velocity impact.
Growth and Defects of Explosives Crystals
Authors: Cady Howard H. 
Published: March 2011

AbstractLarge single crystals of PETN, RDX, and TNT can be grown easily from evaporating ethyl acetate solutions. The crystals all share a similar type of defect that may not be commonly recognized. The defect generates conical faces, ideally mosaic crystals, and may account for the “polymorphs” of TNT and detonator grades of PETN.TATB crystals manufactured by the amination of trichlorotrinitrobenzene in dry toluene entrain two forms of ammonium chloride. One of these forms causes “worm holes” in the TATB crystals that may be the reason for its unusually low failure diameter.Strained HMX crystals form mechanical twins that can spontaneously revert back to theuntwinned form when the straining force is removed. Large strains or temperatures above 100°C lock in the mechanical twins.
Experimental Study and Model Calculations of Metal Combustion in Al/Ap Underwater Explosives
Authors: Miller Philip J. , Guirguis Raafat H. 
Published: March 2011

AbstractA small-scale laboratory experiment in which the detonation products are confined was designed such as to yield for small charges (as little as 1/2 gram) gas expansion rates comparable to those due to the underwater detonation of large-scale charges. The resulting slow expansion allows the aluminum and the other non-ideal components typically used in underwater explosives to react to completion within the time frame of the experiment. Both ideal and non-ideal aluminized explosives were tested. The traditional Jones-Wilkins-Lee (JWL) equation of state reproduced the measurements in the case of the ideal explosives. An extended JWL equation of state in which the time-dependent late energy release is introduced was adjusted until it reproduced the measurements of the non-ideal explosive tested. This derived time-dependent equation of state also reproduced the data of large-scale cylinder tests and underwater detonations using the same non-ideal explosive.
Detonation Studies in Dispersed Solid Particulate Explosives Using High Speed Time-Resolved Holography
Authors: Ehrlich Michael J. , Wagner James W. , Friedman Jacob , Egghart Heinrich 
Published: March 2011

IntroductionClouds of dispersed explosive or combustible solid particles are detonable and such systems may exhibit self-sustained detonation [1–8]. However, the method by which individual particles in the explosive cloud interact to sustain detonation is not well understood. The similar case of liquid fuel/air explosives was investigated in detail during the 1960's and 1970's. For these systems, it was established that incident shock waves serve to shatter large liquid droplets into a mist of micro-droplets. These microdroplets are almost instantaneously accelerated to the convective flow velocity behind the shock wave. The energy released upon ignition of the micromist supports the shock wave and selfsustained detonation results [9–11].
Combustion Synthesis of Composite Materials
Authors: Moore J. J. 
Published: March 2011

AbstractThis paper discusses the of application of combustion synthesis of ceramic and ceramic-metal composites. Several model exothermic combustion synthesis reactions are being used to investigate the effect of reaction parameters, eg. stoichiometry, green density, combustion environment and mode, particle size, physical properties of reactants and products, on the stability and control of the synthesis reaction, product morphology and properties and performance.
Energy Transfer Dynamics and Impact Sensitivity
Authors: Fried Laurence E. , Ruggiero Anthony J. 
Published: March 2011

AbstractIn this paper we focus on the relation between impact sensitivity and energy transfer rates. When a crystal receives an impact, low frequency lattice vibrations (called phonons) are excited. Typical phonon frequencies are 0-200 cm-1. This energy must then be converted to vibron frequencies (1000–2000 cm-1) before bond breaking can occur. We derive a simple formula for the energy transfer rate in terms of the density of vibrational states and the vibron-phonon coupling. We are able to estimate the phonon upconversion rate in widely varying energetic materials such as TATB, HMX, and Pb styphnate by examining existing inelastic neutron scattering data. We find that the estimated energy transfer rates in pure unreacted material are strongly correlated with impact sensitivity.
Time Lag Diffusion Method for a Solid Propellant Emitting Gases
Authors: Baird James K. , Chen Jenn-Shing 
Published: March 2011

AbstractIn the ordinary application of the time-lag method to the measurement of the diffusion coefficient of a gas passing through a plane sheet of an inert solid, the gas is pressurized on one side of the sheet and evacuated on the other. After decay of transients, the cumulative amount, Q(t), of gas diffused through the sheet in time, t, assumes the “time-lag” form, Q(t) = A(t - L). Measurements of the slope, A, and the intercept, L, can be used to determine the diffusion coefficient and the solubility of the gas in the solid. We have rederived this law for the case of a solid which is actively evolving this same gas at an arbitrary rate and have used it to predict the rate of outgasing of the solid upon standing. Practical applications of the theory include radioactive decay of minerals, rejection of plasticizers by plastics, and the decomposition of solid rocket propellants.
Shocked Energetic Molecular Materials: Chemical Reaction Initiation and Hot Spot Formation
Authors: Fayer M. D. , Tokmakoff Andrei , Dlott Dana D. 
Published: March 2011

AbstractA theoretical model is developed to describe multiphonon up-pumping of internal vibrations. The dominant mechanism for up-pumping is anharmonic coupling of excited phonon modes with low frequency molecular vibrations, termed doorway modes. Quantitative calculations were performed which show the extent and rate of multiphonon up-pumping caused by shock excitation. The time dependence of chemical reactivity behind the front is calculated using reaction rate laws for the decomposition of nitramine explosives. A mechanism for hot spot formation, based on defect induced local increases in anharmonic coupling, is discussed.
Relationship Between Radiation Stability and Molecular Structure of Nitramine Explosives
Authors: Pinto James J. 
Published: March 2011

AbstractThe radiation stabilities of the nitramine explosives 1,4-dinitroglycolurile (DINGU), 1,4-dimethyl-2,5-dinitroglycolurile (DMD) and hexanitrohexaazaisowurtzitane (HNIW) have been determined using XPS. Samples were exposed to x-rays for times up to eight hours while photoelectron spectra were recorded in the carbon, oxygen, and nitrogen Is energy regions and mass spectra were recorded of gases evolved during the decomposition process. These data are compared to the previously determined stabilities for cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HlMX). The N1s spectra of the irradiated materials show the NO2 peak decreases relative to the total nitrogen signal while low binding energy peaks grow. The rate of loss of the NO2 peak was fit to first order kinetics and the rate constants obtained show some correlation with the N-N bond strength as measured by the average N-N bond distance and the average NO2 asymetric stretch frequency. Despite the differences in structure of these molecules (DINGU and DMD are bicyclic rings, RDX and HMX are rings and HNIW is a cage) the radiation stability appears to be controlled by the strength of the N-N bond.
Thin Film Infrared Laser Pyrolysis Studies of Thermal Decomposition Mechanisms in Nitramine Propellants
Authors: Botcher Tod R. , Wight Charles A. 
Published: March 2011

AbstractThin films of RDX (1,3,5-trinitro-1,3,5-triazine) have been prepared by vapor deposition onto a 77 K substrate window and pyrolyzed with a pulsed CO2 laser. Each sample is rapidly quenched after the laser pulse by heat conduction into the cold substrate, and the initial reaction products are trapped on the window for examination by transmission FTIR spectroscopy. We have detected N2O4, the dimer of nitrogen dioxide, as an initial condensed phase pyrolysis product, confirming that scission of one of the N-N bonds is the first step in the reaction mechanism. No evidence was found for formation of methylene nitramine via a proposed concerted depolymerization pathway.
Energy Localization and the Initiation of Explosive Crystals by Shock or Impact
Authors: Coffey C. S. 
Published: March 2011

AbstractThe initiation of chemical reaction in explosive crystals during shock or impact is shown to be a solid state, quantum mechanical, process not accessible by a classical continuum approach. The process by which dislocations move in a solid is analyzed in terms of quantum mechanical tunneling. The motion of these dislocations significantly perturbs the lattice and creates phonons which, for low dislocation velocities can cause local ignition sites and for high dislocation velocities, can have energies sufficient to directly pump the internal vibrational modes of the explosive molecules and cause rapid molecular dissociation.