[en] Pressure-volume-temperature data and mass spectrometric results obtained during exposure of PuO₂ to D₂O show that the dioxide reacts with water at room temperature to produce a higher oxide (PuO_2+x)and H₂. Results demonstrate that PuO_2+x is the thermodynamically stable oxide in air. The absence of O₂ at detectable levels in the gas phase implies that radiolytic decomposition of water to the elements is not a significant reaction. The rate of the PuO₂+H₂O reaction is 6±4 nmol H₂/m² day, a value that is independent of the H₂O concentration on the oxide over a range that extends from fractional monolayer coverage to saturation by liquid water. Evaluation of literature data shows that oxide compositions in excess of PuO_2.25 are attained, but the maximum value of x is unknown. During exposure of PuO₂ to a 2:1 D₂:O₂ mixture at room temperature, the elements combine by a process consistent with a surface-catalyzed reaction. Water is simultaneously formed by the H₂+O₂ reaction and consumed by the PuO₂ + H₂O reaction and accumulates until the opposing rates are equal. Thereafter, PuO_2+x is formed at a constant rate by the water-catalyzed PuO₂ + O₂ reaction. The failure of earlier attempts to prepare higher oxides of plutonium is discussed and the catalytic cycle that promotes the reaction of PuO₂ with O₂ is described. Implications of the results for extended storage and environmental chemistry of oxide are examined. Moisture-catalyzed oxidation of PuO₂ accounts for observation of both pressure increases and decreases in oxide storage containers with air atmospheres. Application of the experimental rate results indicates that the reaction of a typical oxide with 0.5 mass % of adsorbed water maybe complete after 25 to 50 years at room temperature

[en] Chemistry and kinetics of air reactions with plutonium monoxide monohydride (PuOH) and with mixtures of the oxide hydride and plutonium metal are defined by results of pressure-volume-temperature (PVT) measurements. Test with specimens prepared by total and partial corrosion of plutonium in 0.05 M sodium chloride solution show that reaction of residual water continues to generate H₂ after liquid water is removed by evacuation. Rapid exposure of PuOH to air at room temperature does not produce a detectable reaction, but similar exposure of a partially corroded metal sample containing Pu and PuOH results in hydride (PuH_x)-catalyzed corrosion of the residual Pu. Kinetics of he first-order reaction resulting in formation of the PuH_x catalyst and of the indiscriminate reaction of N₂ and O₂ with plutonium metal are defined. The rate of the catalyzed Pu+air reaction is independent of temperature (E_a = 0), varies as the square of air pressure, and equals 0.78 ± 0.03 g Pu/cm² min in air at one atmosphere. The absence of pyrophoric behavior for PuOH and differences in the reactivities of PuOH and PuOH + Pu mixtures are attributed to kinetic control by gaseous reaction products. Thermodynamic properties of the oxide hydride are estimated, particle size distributions of corrosion products are presented, and potential hazards associated with products formed by aqueous corrosion of plutonium are discussed

[en] Kinetic studies show that plutonium corrosion in air is catalyzed by plutonium hydride on the metal surface and suggest that the process has caused storage containers to fail. The catalyzed reaction initiates at 25 degrees C, indiscriminately consumes both O₂ and N₂, and transforms metal into a dispersible product at a 10⁷-10¹⁰ faster rate (0.6 ± 0.1 g Pu/cm² min) than normal air oxidation. The catalyzed Pu+O₂ reaction advances into the metal at a linear rate of 2.9 m/h. Rate equations and particle size data, which are presented for catalyzed and atmospheric corrosion at temperatures up to 3500 degrees C, provide a technical basis for more accurately assessing the dispersal hazard posed by plutonium metal

[en] 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_2.4 and PuO_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 PuO₂ indicating that the recombination reaction is faster than radiolytic decomposition of adsorbed water but a chemical reaction produces H₂; (4) PVT studies of the reaction between PuO₂ and water demonstrate that PuO_2+x and H₂ form and that PuO₂ 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

[en] The specific goal of this project was to evaluate the magnitude and practical significance of radiation effects involving mixtures of chloride salts and plutonium dioxide (PuO₂) sealed in stainless steel containers and stored for up to 50 yr, after stabilization at 950 C and packaging according to US Department of Energy (DOE) standards. The potential for generating chemically aggressive molecular chlorine (and hydrogen chloride by interaction with adsorbed water or hydrogen gas) by radiolysis of chloride ions was studied. To evaluate the risks, an annotated bibliography on chloride salt radiolysis was created with emphasis on effects of plutonium alpha radiation. The authors present data from the material identification and surveillance (MIS) project obtained from examination and analysis of representative PuO₂ items from various DOE sites, including the headspace gas analysis data of sealed mixtures of PuO₂ and chloride salts following long-term storage

[en] Kinetic studies show that plutonium corrosion in air is catalyzed by plutonium hydride on the metal surface and causes storage containers to fail. The reaction initiates at 25 C, indiscriminately consumes both O₂ and N₂, and transforms Pu into a dispersible product at a 10⁷-10¹⁰ faster rate (0.6±0.1 g Pu/cm² min) than normal air oxidation. The catalyzed reaction of O₂ advances into the metal at a linear rate of 2.9 m/h. Rate equations and particle size data for atmospheric and catalyzed corrosion at temperatures up to 3500 C provide a technical basis for assessing the dispersal hazard posed by plutonium metal. (orig.)

[en] Characterization of glovebox atmospheres and the black reaction product formed on plutonium surfaces shows that the abnormally rapid corrosion of components in the fabrication line is consistent with a complex salt-catalyzed reaction involving gaseous hydrogen chloride (HCl) and water. Analytical data verify that chlorocarbon and HCl vapors are presented in stagnant glovebox atmospheres. Hydrogen chloride concentrations approach 7 ppm at some locations in the glovebox line. The black corrosion product is identified as plutonium monoxide monohydride (PuOH), a product formed by hydrolysis of plutonium in liquid water and salt solutions at room temperature. Plutonium trichloride (PuCl₃) produced by reaction of HCl at the metal surface is deliquescent and apparently forms a highly concentrated salt solution by absorbing moisture from the glovebox atmosphere. Rapid corrosion is attributed to the ensuing salt-catalyzed reaction between plutonium and water. Experimental results are discussed, possible involvement of hydrogen fluoride (HF) is examined, and methods of corrective action are presented in this report

[en] The termination of operations at many U.S. Department of Energy (DOE) facilities was the result of many factors, including the end of the cold war, the termination of weapons manufacture, as well as significant safety issues found at the facilities. As a result of cessation of operations, the safe storage of nuclear material and nuclear residues from weapons manufacture and research projects became a topic of major importance. The residues are in many forms, including ash, nitrate solutions, oxides of various purity, salts, and glove-box waste. Much of this material has now been stored for more than 5 yr. This paper summarizes the results for the head-space gas sampling, TDMS, and the long term storage studies

[en] The Defense Nuclear Facilities Safety Board (DNFSB) was established by Congress to oversee the operations of U.S. Department of Energy (DOE) facilities for the production of nuclear weapons. On May 26, 1994, the DNFSB approved Recommendation 94-1 requiring the remediation of safety issues after termination of production. After detailed investigation, the DOE issued the Plutonium Working Group report on environmental, safety, and health vulnerabilities of plutonium storage in September 1994. The DOE issued an implementation plan for the 94-1 Recommendation in February 1995, which described activities complexwide to remediate safety problems identified by the DNFSB and the vulnerability assessment . As lead laboratory for plutonium stabilization, Los Alamos National Laboratory (LANL) provides research, development, and testing to accomplish safe storage or disposal of legacy weapons materials

[en] Termination of plutonium part fabrication in the fall of 1989 was followed by the sudden cessation of plutonium processing throughout the U.S. Department of Energy (DOE) complex, leaving reactive residual plutonium legacy materials. There is ∼26 tonnes of plutonium in vulnerable condition located throughout the nuclear complex. This material does not include plutonium, which is safely located in weapons and weapons assemblies. Four sites-Rocky Flats Environmental Technology Site, Westinghouse Hanford Company, Los Alamos National Laboratory (LANL), and Savannah River Site-hold major amounts of plutonium feed materials that must now be stabilized and repackaged. Lawrence Livermore National Laboratory and other sites have lesser amounts