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Gas-Phase Oxidation of Cm+ and Cm2+ -- Thermodynamics of neutral and ionized CmO

Description: Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm+ and Cm2+; parallel studies were carried out with La+/2+, Gd+/2+ and Lu+/2+. Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M+-O](M = Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO+ with dienes, and the second ionization energies, IE[MO+](M = Cm, La, Gd, Lu), from the rates of electron-transfer reactions from neutrals to the MO2+ ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO]= 6.4+-0.2 eV; IE[CmO+]= 15.8+-0.4 eV; D[Cm-O]= 710+-45 kJ mol-1; D[Cm+-O]= 670+-40 kJ mol-1; and D[Cm2+-O]= 342+-55 kJ mol-1. Estimates for the M2+-O bond energies for M = Cm, La, Gd and Lu are all intermediate between D[N2-O]and D[OC-O]--i.e., 167 kJ mol-1< D[M2+-O]< 532 kJ mol-1 -- such that the four MO2+ ions fulfill the thermodynamic requirement for catalytic O-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO2+, LaO2+, GdO2+ and LuO2+ dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO2+ ion appeared during the reaction of Cm+ with O2 when the intermediate, CmO+, was not collisionally cooled -- although its formation is kinetically and/or thermodynamically unfavorable, CmO2+ is a stable species.
Date: December 8, 2008
Creator: Gibson, John K; Haire, Richard G.; Santos, Marta; Pires de Matos, Antonio & Marcalo, Joaquim
Partner: UNT Libraries Government Documents Department

Remote micro-encapsulation of curium-gold cermets

Description: A technique is described for fabricating minature, high-density capsules of curium-244 oxide contained in three concentric jackets of metallic gold (or silver), with the outer surface being free of alpha contamination. The completed capsules are right circular cylinders 0.2500-inch diameter and 0.125-inch tall, with each level of containment soldered (or brazed) closed. A typical capsule would contain approx. 70 mg of /sup 244/Cm (5.7 Ci) mixed with 120 mg of gold powder in the form of a cermet wafer clad in three concentric, 0.010-inch thick, liquid tight jackets. This method of fabrication eliminates voids between the jackets and produces a minimum size, maximum density capsule. Cermet densities of 11.5 g/cc were obtained, with an overall density of 17.3 g/cc for the finished capsule.
Date: October 6, 1980
Creator: Coops, M.S.; Voegele, A.L.; Hayes, W.N. & Sisson, D.H.
Partner: UNT Libraries Government Documents Department

ORNL isotopic power fuels quarterly report for period ending December 31, 1973

Description: Heat soak periods were completed on the remaining 49 couples of the compatibility matrix which was put on test in May 1973. Examination of the 18 couples which were taken off test in August 1973 was completed. The planned short-term ceramic compatibiliiy matrix exposures were completed, and optical microscope examinations were done. Experiments were started to develop fabrication techniques for preparation of an 11-couple compatibility matrix scheduled for FY 1974. The design of this matrix was finalized, and component procurement was started. Free energy calculations were made for the reactions of Cm/sub 2/O/sub 3/ fuel with Haynes 188, Ta-10% W, and TZM alloys and with beryllium. Measurements of the helium release characteristics of hot-pressed / sup 244 Cm/sub 2/O/sub 3/ were started at 500, 650, and 800 deg C. A vapor pressu re determination was run on curium metal in the temperature range from 900 to 1800 deg C. Vapor pressure measurements of/sup 244/Cm/sub 2/O/sub 3/ in the range from 1200 to 1600 deg C were begun these will continue next quarter. Examinations by x-ray diffraction were made on materials resulting from exposures of/sup 244/Cm/sub 2/O/sub 3/ to flowing seawater, boiling scawater, and dry air as well as on/sup 244/Cm/sub 2/O/sub 3/ sam ples taken at various stages in the fuel forming process. The equipment which will be used for emissivity measurements was improved and checked with nonradioactive samples. Observations of two 25-W//sup 244/Cm/sub 2/O/sub 3/ pellets stored in argon ond one 25-W/sup 244/Cm/sub 2/O/sub 3/ pellet stored in dry air continued. A /sup 244/Cm/sub 2/O/ sub 3/ pellet was leac hed with boiling distilled water and the rate of/sup 244/ Cm loss measured. Calculational studies of /sup 244/Cm yields and isotopic abundances from various types of reactor operations were continued. A study of the potentinl fur criticality problems in/sup ...
Date: February 1, 1974
Creator: Lamb, E.
Partner: UNT Libraries Government Documents Department

Effect of physico-chemical properties on metabolism of transuranium oxide aerosols inhaled by beagle dogs

Description: The oxides of four transuranium isotopes ($sup 238$Pu, $sup 239$Pu, $sup 241$Am, and $sup 244$Cm), prepared by identical methods of calcining the oxalate at 750$sup 0$C for two hours, had different physico-chemical properties. For all four oxides the density ranges from 9.8 to 11.4 g cm$sup -3$ and initial ultrafilterability (suspended fraction of activity less than 24 A) varied from 0.002 percent for $sup 239$PuO$sub 2$ to 2.24 percent for $sup 238$PuO$sub 2$. Dogs were exposed by nose-only techniques to aerosols generated by nebulizing water suspensions of the oxides. The dogs were sacrificed at intervals from one week to about a year postexposure. The rate of translocation of material from lung to other tissues increased from $sup 239$Pu to $sup 238$Pu to $sup 241$Am to $sup 244$Cm, possibly reflecting the decrease in mean particle size from an MMD of 0.7 $mu$m to $sup 239$PuO$sub 2$ to 0.6 $mu$m for $sup 238$PuO$sub 2$ to 0.4 $mu$m for $sup 241$AmO$sub 2$ to 0.1 $mu$m for $sup 244$CmO/sub x/. Accumulation of the isotopes in the liver and skeleton as a percentage of final body burden was 1 percent $sup 239$Pu and 7 to 23 percent for $sup 238$Pu at about a year postexposure, while at 270 days postexposure, values were 40 percent for $sup 241$Am and 40 to 30 percent for $sup 244$Cm. (auth)
Date: January 1, 1975
Creator: Craig, D.K.; Park, J.F. & Ryan, J.L.
Partner: UNT Libraries Government Documents Department

Helium release from $sup 244$Cm$sub 2$O$sub 3$

Description: The release of helium from hot-pressed pellets and sol-gel microspheres of /sup 244/Cm/sub 2/0/sub 3/ was investigated under isothermal steady-state release at 900 to 1700 deg C. The release of helium from hot-pressed pellets of coprecipitated 75 mole% /sup 244/Cm/sub 2/O/sub 3/ 25 mole% Gd/sub 2/O/sub 3/ and 46 mole% /sup 244/Cm/sub 2/O/sub 3/-54 mole% Gd/s ub 2/O/sub 3/ was also tnvestigated at 1300 to 170O deg C. Release characteristics could be approximately described by diffusion models. Rationally consistent mechanisms are postulated for the release of helium from /sup 244/Cm/sub 2/O/sub 3/. (auth)
Date: November 1, 1973
Creator: Angelini, P. & McHenry, R.E.
Partner: UNT Libraries Government Documents Department

Experimentally determined neutron and gamma-ray spectra from an encapsulated Cm$sub 2$O$sub 3$ power source

Description: The experimentally determined neutron and gamma ray spectra of a Cm/sub 2/O/sub 3/ spontaneously fissioning source are presented. The neutron spectrum is given for the energy range 30 keV to 10 MeV, while the gamma ray spectrum spans the energy range 205 keV to 12 MeV. (auth)
Date: March 1, 1974
Creator: Freestone, R.M. Jr.
Partner: UNT Libraries Government Documents Department