[en] Detonation of hydrogen and oxygen in stainless steel storage containers produces maximum pressures of 68.5 psia and 426.7 psia. The cylinders contain 3,000 g of PuO₂ with 0.05 wt% and 0.5 wt% water respectively. The hydrogen and oxygen are produced by the alpha decomposition of the water. Work was performed for the Savannah River Site

[en] The free energy, enthalpy and entropy of formation of the compounds Cs₃PuCl₆ and CsPu₂Cl₇ have been determined by measuring the sublimation pressures for the reactions: CsCl(s) = CsCl(g), 2/5 Cs₃PuCl₆(s) = 1/5 CsPu₂Cl₇(s) + CsCl(g), and CsPu₂Cl₇(s) = 2 PuCl₃(s) + CsCl(g). The pressures are measured using Knudsen effusion mass spectrometry over the temperature range 600 to 850 K. For the formation of Cs₃PuCl₆ from CsCl and PuCl₃, ΔG₂₉₈⁰ = -77.3 +/- 8.5 kJ/mole, ΔH₂₉₈⁰ = -82.1 +/- 7.8 kJ mole, and ΔS²⁹⁸⁰ = -16.2 +/- 10.9 J/K mole. For CsPu₂Cl₇, ΔG₂₉₈⁰ = -39.4 +/- 3.5 kJ/mole, ΔH₂₉₈⁰ = -40.8 +/- 3.2 kJ/mole, and ΔS₂₉₈⁰ = -4.6 +/- 4.2 J/K mole

[en] The gaseous dimerization equilibrium 2 UF₅=U₂F₁₀ was studied by high temperature mass spectrometry over the range 600 to 870 K. Gaseous UF₅ monomer and dimer were generated by the reaction of UF₆(g) with a solid phase that was initially UF₄(s), and the abundances of the two species were monitored with both the parent and major fragment ions. Measurements of the U₂F₁₀/UF₅ ratio as a function of pressure established that gaseous equilibrium was achieved. The average of several second-law determinations yielded a value of -39.0 +- 1.0 kcal/mole for the enthalpy of dimerization of UF₅ at 750 K corrected to -40.0 +- 1.0 kcal/mole at 298 K. From an absolute pressure calibration, the equilibrium constant was evaluated, leading to an entropy of dimerization of -40.0 cal/mole deg at 750 K. The results indicate that previously reported transpiration studies on UF₅(s) should be interpreted in terms of vapor transport by U₂F₁₀ (g) rather than UF₅ (g). The enthalpies of sublimation of UF₅ (g) and U₂F₁₀ (g) from UF₅ (s) at 298 K are calculated to be 39.0 and 38.5 kcal/mole, respectively, from the corrected transpiration vapor pressure data and the UF₅ dimerization data reported here. The electron impact mass spectra of UF₆ and UF₅ at several ionizing energies are reported. A weak U₂F⁺₁₁ signal was observed at high UF₆ flow rates, apparently the product of the secondary ion source reaction of UF⁺₅ and UF₆

[en] Precise vapor pressure measurements by target collection/mass spectrometric Knudsen effusion techniques were combined with crystal entropy estimates to produce self-consistent free-enrgy functions, permitting calculation of heats, entropies and free energies from 298⁰K to the highest temperatures of measurement. The vapor pressures and thermodyamics of vaporization of americium, curium, berkelium, and californium are compared in terms of electronic structure and bonding trends in the trans-plutonium elements. These resuslts are contrasted with the behavior of the early actinides, with attention to energy states and possible effects of f-electron bonding. 9 figures, 4 tables

[en] The heterogeneous reaction equilibrium (5/6)MoF₆(g) + (1/6)Mo(s) = MoF₅(g) was studied by mass spectrometry over the range 460 to 525 K, and values of Δsub(r)H⁰/R at 298.15 K derived by the second-law and third-law procedures are in close agreement. From the preferred second-law result, Δsub(f)H⁰/R of MoF₅(g) at 298.15 K is found to be -(149.3 +- 0.5) kK, in good agreement with a value obtained previously from gaseous equilibrium measurements in the Mo + S + F system. Another value for MoF₅(g) derived from the vapor pressure of MoF₅(l) appears to be in error because of an incorrect evaluation of the partial pressure of monomer. The primary bond-dissociation function is found to be 47.6 kK, compared with the average value of 53.8 kK in MoF₆. Gas-solid equilibrium in the MoF₆ + MoF₅ + Mo system is attained rapidly at the low temperatures and pressures of these experiments, once a 'clean' Mo surface is generated. (author)

[en] Short note

[en] The vapor pressure of high purity ²⁴³Am metal has been measured over the temperature range 1200--1600 K, using combined target and mass spectrometric Knudsen effusion techniques. This work was performed to extend data into the liquid phase, and to compare results with earlier ²⁴¹Am experiments. Second-law and third-law heats of vaporization are in close agreement with the earlier work, and no isotope effect was found. An additional study of the vaporization of ²⁴³Am from a liquid La host was made to explore solubility relationships and activities for systems with similar electronic properties. Lanthanum was found to be a nearly ideal solvent, giving the correct heat of vaporization for Am, and activity coefficients slowly changing with temperature, representative of the effects of a small heat of mixing

[en] Precise vapor pressure measurements by target collection/mass spectrometric Knudsen effusion techniques were combined with crystal entropy estimates to produce self-consistent free-energy functions, permitting calculation of heats, entropies and free energies from 298 K to the highest temperatures of measurement. The vapor pressures and thermodynamics of vaporization of americium, curium, berkelium, and californium are compared in terms of electronic structure and bonding trends in the transplutonium elements. These results are contrasted with the behavior of the early actinides, with attention to energy states and possible effects of f-electron bonding. 9 figures, 4 tables

[en] The enthalpy of sublimation for the reaction PuF₃(s)→PuF₃(g) over the range 1127 to 1280 K was measured to be 413.8±16.4kJ/mol for the PuF₂⁺/PuF₃ ion intensity and 412.0±35.7kJ/mol for the PuF₃⁺/PuF₃ ion intensity. Combining this data with the measurements of other investigators gives ΔH_s⁰(298 K)=429.5±4.7 kJ/mol for the enthalpy of sublimation of PuF₃(s). (orig.)

[en] The ionization potentials of the molecules PuF₅, PuF₄, and PuF₃ have been measured using electron impact ionization. The values are, respectively, 14.5 +- 0.1, 11.8 +- 0.4, and 8.6 +- 0.5 eV. The parent ion PuF⁺₆ was not detected. From the ionization potentials and the fragment ion appearance potentials the bond dissociation energies of the molecules F₅Pu--F, F₄Pu--F, F₃Pu--F, and F₂Pu--F have been calculated to be 53 +- 2, 108 +- 12, 113 +- 5, and 141 +- 16 kcal/mol, respectively. Upon comparison with data available on the plutonium fluorides the bond energies of F₃Pu--F and F₂Pu--F are accurate to within the stated uncertainty. The values of the bond energies of F₅Pu--F and F₄Pu--F disagree with the reported enthalpy of formation of PuF₆(s). Analysis of available data indicates that the enthalpy of formation of PuF₆(s) is most likely -484 +- 10 kcal/mol