81 Matching Results

Search Results

Advanced search parameters have been applied.

EVALUATION OF FIRE HAZARDS WHILE REPACKAGING PLUTONIUM-CONTAMINATED SCRAP IN HB-LINE

Description: The potential for a fire while repackaging plutonium-contaminated scrap was evaluated. The surface-to-mass ratio indicates the metal alone will not spontaneously ignite. Uranium hydride can form when uranium metal is exposed to water vapor or hydrogen; uranium hydride reacts rapidly and energetically with atmospheric oxygen. The plutonium-contaminated scrap has been inside containers qualified for shipping, and these containers are leak-tight. The rate of diffusion of water vapor through the seals is small, and the radiolytic hydrogen generation rate is low. Radiography of samples of the storage containers indicates no loose oxide/hydride powder has collected in the storage container to date. The frequently of a fire while repackaging the plutonium-contaminated scrap is extremely unlikely.
Date: December 18, 2003
Creator: Hallman, D
Partner: UNT Libraries Government Documents Department

Explosive Potential Analysis of AB Process-Final Report

Description: A need arose to define the hazards associated with the operation of a process. The process involved the evolution of a hydrogen gas stream from thermal decomposition of uranium hydride at approximately 400 C into the interior of a purged argon-filled glove box. Specific hazards of interest included the potential reaction severity of the evolved hydrogen with atmospheric oxygen, either downstream in the vent system or inside the box in the event of serious air inleakage. Another hazard might be the energetic reaction of inleaked air with the hot uranium and uranium hydride powder bed, possibly resulting in the dispersion of powders into an air atmosphere and the rapid combustion of the powders. This was approached as a problem in calculational simulation. Given the parameters associated with the process and the properties of the glove box system, certain scenarios were defined and the potential for flammable or detonation reactions estimated. Calculation tools included a comprehensive fluid dynamics code, a spreadsheet, a curve-fitting program, an equation solver, and a thermochemistry software package. Results are reported which suggest that the process can be operated without significant hazard to operators or significant damage to equipment, assuming that operators take account of potential upset scenarios.
Date: October 12, 2001
Creator: Bullock, J.S.; Giles, G.E. jr.; Wendel, M.W. & Sulfredge, C.D.
Partner: UNT Libraries Government Documents Department

The influence of surface morphology and oxide microstructure on the nucleation and growth of uranium hydride on alpha uranium

Description: While the bulk kinetics of the uranium-hydrogen reaction are well understood, the mechanisms underlying the initial nucleation of uranium hydride on uranium remain controversial. In this study, the authors have employed environmental cell optical microscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy, (AFM) in an attempt to relate the structure of the surface and the microstructure of the substrate with the susceptibility and site of hydride nucleation. Samples have been investigated with varying grain size, inclusion (carbide) concentration, and thermal history. There is a clear correlation to heat treatment immediately prior to hydrogen exposure. Susceptibility to hydride formation also appears to be related to impurities in the uranium. The oxidized surface is very complex, exhibiting wide variations in thickness and topography between samples, between grains in the same sample, and within individual grains. It is, however, very difficult to relate this fine scale variability to the relatively sparse hydride initiation sites. Therefore, the surface oxide layer itself does not appear to control the sites where hydride attack is initiated, although it must play a role in the induction period prior to hydride initiation.
Date: December 31, 1998
Creator: Hanrahan, R.J. Jr.; Hawley, M.E. & Brown, G.W.
Partner: UNT Libraries Government Documents Department

Tritium transport vessel using depleted uranium

Description: A tritium transport vessel using depleted uranium was tested in the laboratory using deuterium and protium. The vessel contains 0.5 kg of depleted uranium and can hold up to 18 grams of tritium. The conditions for activation, tritium loading and tritium unloading were defined. The safety aspects that included air-ingress, tritium diffusion, temperature and pressure potentials were evaluated.
Date: January 1995
Creator: Heung, L. K.
Partner: UNT Libraries Government Documents Department

Rapid hydrogen gas generation using reactive thermal decomposition of uranium hydride.

Description: Oxygen gas injection has been studied as one method for rapidly generating hydrogen gas from a uranium hydride storage system. Small scale reactors, 2.9 g UH{sub 3}, were used to study the process experimentally. Complimentary numerical simulations were used to better characterize and understand the strongly coupled chemical and thermal transport processes controlling hydrogen gas liberation. The results indicate that UH{sub 3} and O{sub 2} are sufficiently reactive to enable a well designed system to release gram quantities of hydrogen in {approx} 2 seconds over a broad temperature range. The major system-design challenge appears to be heat management. In addition to the oxidation tests, H/D isotope exchange experiments were performed. The rate limiting step in the overall gas-to-particle exchange process was found to be hydrogen diffusion in the {approx}0.5 {mu}m hydride particles. The experiments generated a set of high quality experimental data; from which effective intra-particle diffusion coefficients can be inferred.
Date: September 1, 2011
Creator: Kanouff, Michael P.; Van Blarigan, Peter; Robinson, David B.; Shugard, Andrew D.; Gharagozloo, Patricia E.; Buffleben, George M. et al.
Partner: UNT Libraries Government Documents Department

Uranium for hydrogen storage applications : a materials science perspective.

Description: Under appropriate conditions, uranium will form a hydride phase when exposed to molecular hydrogen. This makes it quite valuable for a variety of applications within the nuclear industry, particularly as a storage medium for tritium. However, some aspects of the U+H system have been characterized much less extensively than other common metal hydrides (particularly Pd+H), likely due to radiological concerns associated with handling. To assess the present understanding, we review the existing literature database for the uranium hydride system in this report and identify gaps in the existing knowledge. Four major areas are emphasized: {sup 3}He release from uranium tritides, the effects of surface contamination on H uptake, the kinetics of the hydride phase formation, and the thermal desorption properties. Our review of these areas is then used to outline potential avenues of future research.
Date: August 1, 2010
Creator: Shugard, Andrew D.; Tewell, Craig R.; Cowgill, Donald F. & Kolasinski, Robert D.
Partner: UNT Libraries Government Documents Department

Reactions of plutonium and uranium with water: Kinetics and potential hazards

Description: The chemistry and kinetics of reactions between water and the metals and hydrides of plutonium and uranium are described in an effort to consolidate information for assessing potential hazards associated with handling and storage. New experimental results and data from literature sources are presented. Kinetic dependencies on pH, salt concentration, temperature and other parameters are reviewed. Corrosion reactions of the metals in near-neutral solutions produce a fine hydridic powder plus hydrogen. The corrosion rate for plutonium in sea water is a thousand-fold faster than for the metal in distilled water and more than a thousand-fold faster than for uranium in sea water. Reaction rates for immersed hydrides of plutonium and uranium are comparable and slower than the corrosion rates for the respective metals. However, uranium trihydride is reported to react violently if a quantity greater than twenty-five grams is rapidly immersed in water. The possibility of a similar autothermic reaction for large quantities of plutonium hydride cannot be excluded. In addition to producing hydrogen, corrosion reactions convert the massive metals into material forms that are readily suspended in water and that are aerosolizable and potentially pyrophoric when dry. Potential hazards associated with criticality, environmental dispersal, spontaneous ignition and explosive gas mixtures are outlined.
Date: December 1, 1995
Creator: Haschke, J.M.
Partner: UNT Libraries Government Documents Department

Quality experimental and calculated powder x-ray diffraction

Description: For several years, we have submitted quality powder XRD patterns to the International Centre for Diffraction Data for inclusion as reference standards in their Powder Diffraction File. The procedure followed is described; examples used are {beta}-UH{sub 3}, {alpha}- BaT{sub 2}, alpha-lithium disilicate ({alpha}-Li{sub 2}Si{sub 2}O{sub 5}), and 2,2`,4,4`,6,6`hexanitroazobenzene-III (HNAB-III).
Date: August 1996
Creator: Sullenger, D. B.; Cantrell, J. S.; Beiter, T. A. & Tomlin, D. W.
Partner: UNT Libraries Government Documents Department

Chemical Reactivity Testing for the National Spent Nuclear Fuel Program. Quality Assurance Project Plan

Description: This quality assurance project plan (QAPjP) summarizes requirements used by Lockheed Martin Energy Systems, Incorporated (LMES) Development Division at Y-12 for conducting chemical reactivity testing of Department of Energy (DOE) owned spent nuclear fuel, sponsored by the National Spent Nuclear Fuel Program (NSNFP). The requirements are based on the NSNFP Statement of Work PRO-007 (Statement of Work for Laboratory Determination of Uranium Hydride Oxidation Reaction Kinetics.) This QAPjP will utilize the quality assurance program at Y-12, QA-101PD, revision 1, and existing implementing procedures for the most part in meeting the NSNFP Statement of Work PRO-007 requirements, exceptions will be noted.
Date: January 24, 1999
Creator: Newsom, H.C.
Partner: UNT Libraries Government Documents Department

Analysis of Hazards Associated with a Process Involving Uranium Metal and Uranium Hydride Powders

Description: An analysis of the reaction chemistry and operational factors associated with processing uranium and uranium hydride powders is presented, focusing on a specific operation in the Development Division which was subjected to the Job Hazard Analysis (JHA) process. Primary emphasis is on the thermodynamic factors leading to pyrophoricity in common atmospheres. The discussion covers feed powders, cold-pressed and hot-pressed materials, and stray material resulting from the operations. The sensitivity of the various forms of material to pyrophoricity in common atmospheres is discussed. Operational recommendations for performing the work described are given.
Date: May 1, 2000
Creator: Bullock, J.S.
Partner: UNT Libraries Government Documents Department

Uranium Hydride Nucleation Kinetics: Effects of Oxide Thickness and Vacuum Outgassing

Description: Many factors such as impurities in the oxide and metal, microstructure, gas impurities, and oxide thickness may influence the rate and location of the nucleation of hydride on uranium. This work has concentrated on isolating one of these variables, the oxide thickness, and measuring the effect of the oxide thickness on uranium hydride nucleation. Uranium samples, all from the same lot, were prepared with different oxide thicknesses. The oxide thickness was measured using Rutherford Backscattering Spectroscopy. Oxidized uranium samples were then exposed to ultra-high purity hydrogen gas under constant volume conditions. Decreases in pressure indicated hydrogen uptake by the sample. The time for hydride nucleation--as well as the maximum hydriding rate--was then calculated from the measured decreases in pressure. The time to nucleate a hydride was found to increase whereas the maximum hydriding rate was found to decrease with increasing oxide thickness. The density of hydride pits also decreased with increasing oxide thickness. The observed results support the argument that the nucleation of hydride is controlled somewhat by diffusion of hydrogen through the oxide layer. Vacuum outgassing of samples, thereby removing the oxide impurities and keeping the oxide thickness constant, dramatically decreased the nucleation time and increased the maximum hydriding rate. Again, this is consistent with hydrogen diffusion through the oxide controlling the nucleation of hydride. Impurities in the oxide layer can decrease the diffusivity of hydrogen and therefore delay the nucleation of uranium hydride.
Date: March 1, 2001
Creator: Teter, David F.; Hanrahan, Robert J. & Wetteland, Christopher J.
Partner: UNT Libraries Government Documents Department

ToF-SIMS study of polycrystalline uranium after exposure to deuterium

Description: Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is employed to examine specific features observed on a polycrystalline depleted uranium sample after exposure to high purity D{sub 2} gas. The ToF-SIMS investigation, being the first of its kind on uranium, investigates a site where the deuterated form of uranium hydride (UD{sub 3}) is clearly observed to have broken through the thin, air-formed oxide. Density functional theory calculations have been performed, which confirm the stability of, and also assign structural geometries to, the various uranium containing fragments observed with SIMS. An inclusion site was also investigated using ToF-SIMS, and these data suggest that the edges of such inclusions exhibit increased D ion, and hence H ion, diffusion when compared to the surrounding surface oxide. These results offer support to the previously published hypotheses that inclusion sites on uranium surfaces exhibit an increased probability to form hydride sites under H{sub 2} exposure.
Date: January 19, 2006
Creator: Morrall, P; Price, D; Nelson, A; Siekhaus, W; Nelson, E; Wu, K J et al.
Partner: UNT Libraries Government Documents Department