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Download or read book Aqueous Dissolution Rates of Uranium Oxides written by and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (684 download)
Download or read book Comparison and Modeling of Aqueous Dissolution Rates of Various Uranium Oxides written by and published by . This book was released on 1996 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Purpose of this work was to measure and model the intrinsic dissolution rates of U oxides under a variety of well-controlled conditions that are relevant to a geologic repository. When exposed to air at elevated temperature, spent fuel may form the stable phase U3O. Dehydrated schoepite, UO3·H2O, exists in drip tests on spent fuel. Equivalent sets of U3O and UO3·H2O dissolution experiments allowed a systematic examination of the effects of temperature (25-75 C), pH(8-10), and carbonate (2-200x10−4molar) concentrations at atmospheric oxygen conditions. Results indicate that UO3·H2O has a much higher dissolution rate (at least tenfold) than U3O under the same conditions. The intrinsic dissolution rate of unirradiated U3O8 is about twice that of UO2. Dissolution of both U3O8 and UO3·H2O shows a very high sensitivity to carbonate concentration. Present results show a 25 to 50-fold increase in room-temperature UO3·H2O dissolution rates between the highest and lowest carbonate concentrations. As with the UO2 dissolution data, the classical observed chemical kinetic rate law was used to model the U3O8 dissolution rate data. The pH did not have much effect on the models, in agreement with earlier analysis of the UO2 and spent fuel dissolution data. However, carbonate concentration, not temperature, had the strongest effect on the U3O8 dissolution rate. The U3O8 dissolution activation energy was about 6000 cal/mol, compared with 7300 and 8000 cal/mol for spent fuel and UO2, respectively.
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ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (685 download)
Download or read book Comparison of Uranium Dissolution Rates from Spent Fuel and Uranium Dioxide written by and published by . This book was released on 1994 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two similar sets of dissolution experiments, resulting from a statistical experimental design were performed in order to examine systematically the effects of temperature (25--75°C), dissolved oxygen (0.002-0.2 atm overpressure), pH (8--10) and carbonate concentrations (2--200 x 10−4 molar) on aqueous dissolution of UO2 and spent fuel. The average dissolution rate was 8.6 mg/m2·day for UO2 and 3.1 mg/m2·day for spent fuel. This is considered to be an insignificant difference; thus, unirradiated UO2 and irradiated spent fuel dissolved at about the same rate. Moreover, regression analyses indicated that the dissolution rates of UO2 and spent fuel responded similarly to changes in pH, temperature, and carbonate concentration. However, the two materials responded very differently to dissolved oxygen concentration. Approximately half-order reaction rates with respect to oxygen concentration were found for UO2 at all conditions tested. At room temperature, spent fuel dissolution (reaction) rates were nearly independent of oxygen concentration. At 75°C, reaction orders of 0.35 and 0.73 were observed for spent fuel, and there was some indication that the reaction order with respect to oxygen concentration might be dependent on pH and/or carbonate concentration as well as on temperature.
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ISBN 13 :
Total Pages : 3 pages
Book Rating : 4.:/5 (683 download)
Download or read book Uranium Dioxide Dissolution Under Acidic Aqueous Conditions written by and published by . This book was released on 1995 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding of the long-term dissolution of waste forms in groundwater is required for the safe disposal of high level nuclear waste in a geologic repository, because waste-form radionuclides could be released by dissolution and transported in groundwater. The dissolution of the uranium dioxide (UO2) matrix in spent nuclear fuel is considered the rate-limiting step for release of radioactive fission products. The intrinsic UO2 dissolution rate sets an upper limit on the aqueous radionuclide release rate. Unsaturated spent fuel tests have shown that pH's of leachates have decreased to a range of 4 to 6, presumably due to air radiolysis that oxidizes nitrogen, producing nitric acid. Dissolution rates under such acidic conditions may be different than those previously reported for alkaline groundwater conditions. No dissolution rate measurements of UO2 or spent fuel have been reported for acidic conditions possibly relevant to a geologic repository. The purpose of our work has been to measure the intrinsic dissolution rates of uranium dioxide under acidic conditions that are relevant to a repository and allow for modeling. Experiments have been completed at room-temperature and 75 C, pH's of 4 and 6, and air and oxygen saturated aqueous solutions. These are compared with earlier work on spent fuel and UO2 using alkaline solutions.
Author : L. M. Ferris
Publisher :
ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.3/5 (91 download)
Download or read book Aqueous Processes for Dissolution of Uranium-molybdenum Alloy Reactor Fuel Elements written by L. M. Ferris and published by . This book was released on 1961 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : W. E. Schortmann
Publisher :
ISBN 13 :
Total Pages : 132 pages
Book Rating : 4.3/5 (91 download)
Download or read book Kinetics of the Dissolution of Uranium Dioxide in Carbonate-bicarbonate Solutions written by W. E. Schortmann and published by . This book was released on 1958 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : M. J. Nicol
Publisher :
ISBN 13 : 9780869990063
Total Pages : 23 pages
Book Rating : 4.9/5 (9 download)
Download or read book Anodic Dissolution of UO2 in Aqueous Solutions written by M. J. Nicol and published by . This book was released on 1972 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (684 download)
Download or read book The Dissolution of Uranium Oxides in HB-Line Phase 1 Dissolvers written by and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of characterization and dissolution studies has been performed to define flowsheet conditions for the dissolution of uranium oxide materials in dissolvers. The samples selected for analysis were uranium oxide materials. The selection of these uranium oxide materials for characterization and dissolution studies was based on high enriched uranium content and trace levels of plutonium. Test results from the characterization study identified ferric oxide (Fe2O3) and iron/chromium/nickel (Fe/Cr/Ni) particles as impurities along with the tri-uranium oxide (U3O8) and uranium trioxide (UO3). The weight percent uranium in this material was found to vary depending on the impurity content. The trace impurity plutonium appears to be associated with the Fe/Cr/Ni particles. A small amount of absorbed moisture and waters of hydration is present. Most of the uranium oxides easily dissolved in low-molar nitric acid solutions without fluoride within one to two hours at solution temperature s between 60-80 degrees C.A small amount of residue remained following this dissolution step. To assure complete dissolution of uranium from these oxide materials, an additional dissolution step at 90 degrees C to boiling for at least one to two hours has been suggested. Only trace amounts of iron associated with Fe2O3 and Fe/Cr/Ni particles will dissolve during the dissolution steps. Neither hydrogen nor heat will be generated during the dissolution of these uranium oxide materials in nitric acid solutions. Some brown nitrogen dioxide (NO2) fumes will be generated during the dissolution of U3O8.
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ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (957 download)
Download or read book Exploration of Basic Dissolution Chemistry of Irradiated Uranium Oxides as Applied to Slug Rupture Decontamination in Recycling Reactor Water Systems written by and published by . This book was released on 1952 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Resume of Uranium Oxide DATA--VII. written by and published by . This book was released on 1956 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A survey of development in preparation and properties of uranium dioxide was made, including powder preparation, physical measurements, fabrication and sintering, stability in water, kinetics in water, UO/sub 2/ --O/sub 2/ equilibrium and kinetics, diffusion studies, in-pile gas release, UO/sub 2/ dissolution rates, and nickel plating of UO/sub 2/ pellets for recoil experiments. The UO/sub 2/ irradiation test program is described, including steam oxidized MCW UO/sub 2/, hot pressed MCW UO/sub 2/, experiments with UO/sub 2/ rods containing 0.2 wt.% TiO/sub 2/, experimental irradiation of natural UO/sub 2/ rods, power cycling of PWR reference UO/sub 2/ fuel rods, density vs. fission product release in hot water, the second PWR bundle proof test, a statistical irradation experiment, and defect tests on Chalk River UO/sub 2/. Contributions from Battelle Memorial Inst. ceramic studies, physical and electrical property investigation of uranium oxides, and kinetics of zircorium --uranium dioxide reactions are presented. A uranium dioxide panel report from Corning Glass Works concerning rupture tests on uranium dioxide compacts, sintering methods, and corrosion tests is presented along with a summary of the uranium dioxide program at MCW, and fit tolerance tests at Hanford. Contributions for the uranium dioxide Panel sponsored by WAPD concerning physical property, fabrication, and mechanical property data are presented along with a note on the melting point of uranium dioxide from work done at KAPL. (J.R.D.).
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ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (685 download)
Download or read book Modeling of UO2 Aqueous Dissolution Over a Wide Range of Conditions written by and published by . This book was released on 1993 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previously it was not possible to predict reliably the rate at which spent fuel would react with groundwater because of conflicting data in the literature. The dissolution of the UO2 spent fuel matrix is a necessary step for aqueous release of radioactive fission products. Statistical experimental design was used to plan a set of UO2 dissolution experiments to examine systematically the effects of temperature (25--75C), dissolved oxygen (0.002--0.2 atm overpressure), pH (8--10) and carbonate (2-200 x 10−4 molar) concentrations on UO2 dissolution. The average uranium dissolution rate was 4.3 mg/m2/day. The regression fit of the data indicate an Arrhenius type activation energy of 8750 cal/mol and a half-power dependence on dissolved oxygen in the simulated groundwater.
Author : John D. Eichenberg
Publisher :
ISBN 13 :
Total Pages : 198 pages
Book Rating : 4.3/5 (91 download)
Download or read book Effects of Irradiation on Bulk UO2 written by John D. Eichenberg and published by . This book was released on 1957 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 29 pages
Book Rating : 4.:/5 (727 download)
Download or read book Dissolution Characteristics of Mixed UO2 Powders in J-13 Water Under Saturated Conditions written by and published by . This book was released on 1991 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Yucca Mountain Project/Spent Fuel program at Argonne National Laboratory is designed to determine radionuclide release rates by exposing high-level waste to repository-relevant groundwater. To gain experience for the tests with spent fuel, a scoping experiment was conducted at room temperature to determine the uranium release rate from an unirradiated UO2 powder mixture (14.3 wt % enrichment in 235U) to J-13 water under saturated conditions. Another goal set for the experiment was to develop a method for utilizing isotope dilution techniques to determine whether the dissolution rate of UO2 matrix is in accordance with an existing kinetic model. Results of these analyses revealed unequal uranium dissolution rates from the enriched and depleted portions of the powder mixture because of undisclosed differences between them. Although the presence of this inhomogeneity has precluded the application of the kinetic model, it also provided an opportunity to elaborate on the utilization of isotope dilution data in recognizing and quantifying such conditions. Detailed listings of uranium release and solution chemistry data are presented. Other problems commonly associated with spent fuel, such as the effectiveness of filtering media, the existence of uranium concentration peaks during early stages of the leach tests, the need for concentration corrections due to water replenishments of sample volumes, and experience derived from isotope dilution data are discussed in the context of the present results. 10 refs., 5 figs., 7 tabs.
Author : Timothy G. Adams
Publisher :
ISBN 13 :
Total Pages : 77 pages
Book Rating : 4.:/5 (857 download)
Download or read book Dissolution of Uranium Dioxide Microspheres in Carbonate and Hydrogen Peroxide Solutions written by Timothy G. Adams and published by . This book was released on 2013 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt: Uranium dioxide has been used in industry both as a fuel for power reactors and as a target for the production of radioisotopes. One of the most important radioisotopes produced using these targets is molybdenum-99 (Mo-99, 65.94hr half-life), which is the parent isotope to technetium-99m (Tc-99m, 6.01hr half-life), a radioisotope used in 70% of diagnostic medical isotope procedures performed in the United States of America. [1] [2] Molybdenum-99, produced by either the thermal neutron fission of uranium-235 in nuclear reactors or by neutron activation of molybdenum-98, is purified, packaged, and shipped to hospitals worldwide. The maximal activity of Tc-99m is reached in 22.9hrs, so it can be milked from the parent Mo-99 repeatedly. Mo-99 is one of many fission products generated during the thermal neutron fission of uranium-235. For production of Mo-99, irradiation targets based on metallic uranium, uranium alloys, or uranium dioxide are produced. After neutron irradiation in a reactor, the uranium target must first be dissolved in a suitable medium. This has traditionally been done using boiling nitric acid solutions. In literature and in industry, the use of alkaline solutions, specifically carbonate salt solutions combined with hydrogen peroxide, are being explored as an alternative to the nitric acid based dissolution process. The carbonate-peroxide dissolution scheme has several advantages over traditional nitric acid dissolutions including less damage to equipment during operation and smaller volumes of waste produced during process. This thesis research work explores the initial dissolution rates of uranium dioxide in carbonate medium containing hydrogen peroxide. Effect of three different counter cations- ammonium, sodium, and potassium - on the dissolution behavior of uranium was investigated. The kinetic factors of dissolution, activation energy, frequency factor, and reaction order with respect to both the carbonate salt and hydrogen peroxide were found for each of these systems. Information in this thesis is organized into six chapters and list of cited literature sources.
Download or read book Dissolving Uranium Oxide--aluminum Fuel written by and published by . This book was released on 1973 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dissolution of aluminum-clad uranium oxide-aluminum fuel was studied to provide basic data for dissolving this type of enriched uranium fuel at the Savannah River Plant. The studies also included the dissolution of a similar material prepared from scrap uranium oxides that were to be recycled through the solvent extraction process. The dissolving behavior of uranium oxide-aluminum core material is similar to that of U-Al alloy. Dissolving rates are rapid in HNO/sub 3/-Hg(NO/sub 3/)/sub 2/ solutions. Irradiation reduce s the dissolving rate and increases mechanical strength. A dissolution model for use in nuclear safety analyses is developed, . based on the observed dissolving characteristics. (auth).
Author : Peter C. Burns
Publisher : Walter de Gruyter GmbH & Co KG
ISBN 13 : 1501509195
Total Pages : 696 pages
Book Rating : 4.5/5 (15 download)
Download or read book Uranium written by Peter C. Burns and published by Walter de Gruyter GmbH & Co KG. This book was released on 2018-12-17 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 38 of Reviews in Mineralogy provides detailed reviews of various aspects of the mineralogy and geochemistry of uranium. We have attempted to produce a volume that incorporates most important aspects of uranium in natural systems, while providing some insight into important applications of uranium mineralogy and geochemistry to environmental problems. The result is a blend of perspectives and themes: historical (Chapter 1), crystal structures (Chapter 2), systematic mineralogy and paragenesis (Chapters 3 and 7), the genesis of uranium ore deposits (Chapters 4 and 6), the geochemical behavior of uranium and other actinides in natural fluids (Chapter 5), environmental aspects of uranium such as microbial effects, groundwater contamination and disposal of nuclear waste (Chapters 8, 9 and 10), and various analytical techniques applied to uranium-bearing phases (Chapters 11-14). This volume was written in preparation for a short course by the same title, sponsored by the Mineralogical Society of America, October 22 and 23, 1999 in Golden, Colorado, prior to MSA's joint annual meeting with the Geological Society of America.
Author : John Baker Hunt
Publisher :
ISBN 13 :
Total Pages : 146 pages
Book Rating : 4.:/5 (494 download)
Download or read book The Dissolution of Uranium Hydride in Aqueous Solutions written by John Baker Hunt and published by . This book was released on 1962 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
