Total pressure of uranium-bearing species over molten urania

Reedy, Gerald T.; Chasanov, M.G.

doi:10.1016/0022-3115(72)90085-2

Cited by 33 publications

(15 citation statements)

References 6 publications

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“…The two balance equations (2)(3)(4) and (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) are coupled through the two fluxes jg and q.…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

“…T(x,O) = To and C 0 (x,O) = cg @ t=O (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) where T 0 is the initial temperature before laser impingement and cg is the initial mass concentration of oxygen.…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

“…The mass balance for oxygen atoms at the interphase boundary gives: jg = j8 + vq @ x=O (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) where C~ is the mass concentration of oxygen atom of the solid at the surface, j8 is the total vaporization mass flux of oxygen in the gas phase. The latter is:…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

“…The surface recession velocity, v, is the ratio of the evaporation mass flux of uranium-bearing species j6 and the mass concentration of uranium atom in the solid Cu, (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) The sign convention is that a flux (mass or heat) is positive if it is in the positive x direction.…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

“…[<l>J L = .J27T~jRT s mole/ em 2 -sec (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) where Ts is the surface temperature and Pi is the equilibrium pressure of species i over the solid at the surface composition and temperature. The vaporization coefficient is assumed to be unity.…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

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Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

Tsai¹,

Olander

1981

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Prof. D. R. Olander Chairman of CommitteeSafety analyses of nuclear reactors require knowledge of the evaporation behavior of U0 2 at temperatures well above the melting point of 3140 K. In this study, rapid transient heating of a small spot on a U0 2 specimen was accomplished by a laser pulse, which generates a surface temperature excursion. This in turn vaporizes the target surface and the gas expands into vacuum.The surface temperature transient was monitored by a fast-response automatic optical pyrometer. The maximum surface temperatures investigated range from -3700 K to -4300 K. A computer program was developed to simulate the laser heating process and calculate the surface temperature evolution. The effect of the uncertainties of the high temperature material properties on the calculation was included in a sensitivity study for U0 2 vaporization. The measured surface temperatures were in satisfactory agreements. No dimer signal of any vapor molecule was measured, indicating the absence of condensation in the highly supersaturated vapor leaving the surface.A shock wave structure is developed by laser pulsing on a U0 2 target in an ambient inert gas. This structure was photographed during the laser pulse. By applying the Mack disk formula, the total vapor pressure corresponding to maximum temperature was obtained. The resulting low vapor pressure and low heat of vaporization deduced from this measurement is attributed to excessively high surface temperature measured due to nonequilibrium radiation from the hot vapor.Additional diagnostics of the phenomenum included collection of the vapor blowoff on disks followed by neutron activation to determine the angular distribution of the vaporization process. The extent of droplet production was also investigated by disk collection. Liquid droplets are observed, but the quantity of U0 2 they contained was insignificant compared to the total mass evaporated.

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“…The two balance equations (2)(3)(4) and (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) are coupled through the two fluxes jg and q.…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

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Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

Tsai¹,

Olander

1981

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Vapour Pressure Studies Over Liquid Uranium Oxide and Uranium Plutonium Oxide Up to 5000 K

Ohse¹,

Babelot²,

Brumme

et al. 1976

Ber Bunsenges Phys Chem

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The estimation of the energy release in a hypothetical fast breeder reactor core meltdown accident requires a detailed analysis of the disassembly process. Since the vapour pressure presents the ultimate shut-down mechanism, the required data are given by the equation of state of the irradiated fuel. The pressure over the ternary uranium-plutonium oxide was determined to logp(atm) = 7.966 -28,137/T, yielding a heat of evaporation of AH,,,, = 128.7 kcal/mol, fully consistent with the heat of sublimation of AHrub = 148.4 kcal/mol below the melting point, and the heat of fusion of 19.4 kcal/mol. The corresponding equation for liquid U 0 2 was determined as logp(atm) = 7.7 -27,900/T, with a heat of evaporation of AHcrap = 127.6 kcal/mol, again in consistency with the assessed data below the melting point of AH,,, = 144.1 kcal/mol, and the heat of fusion of 17.7 kcal/mol. For this a new high-energy laser technique, including fast temperature recording in the microsecond range, was developed. The first quantitative measurements on (U, Pu)02 above 4000 K were reported to the IAEA Symposium on Thermodynamics of Nuclear Materials in Vienna. The investigation of the total temperature range from 3000 K to T, = 7560 K revealed two principle experimental difficulties, a liquid layer movement at temperatures below 4000 K, and optical absorption due to increasing thermal ionisation above 5000 K. A new double intensity laser pulse technique is presented, which allows the extension of measurements to below 4000 K. In addition a multi-wavelength pyrometer technique has been developed to eliminate, and at a later stage to determine, spectral ernissivities above the melting point, during laser heating within pulse times of micro and nanoseconds.Die Abschatzung der freiwerdenden Energie bei einem hypothetischen Unfall eines schnellen Brutreaktors bedarf einer detaillierten Analyse des Zetstorungsprozesses. Da der Dampfdruck den endgiiltigen ,,Shut-down"-Mechanismus kontrolliert, sind die benotigten Daten durch die Zustandsgleichung des bestrahlten Brennstoffs bestimmt. Der Druck uber dem ternaren Uran-Plutonium-Oxid wurde zu logp(atm) = 7,966 -28 137/T ermittelt. Dies ergibt eine Verdampfungsenthalpie von AHverd = 128,7 kcal/mol, in voller nbereinstimmung mit der Sublimationsenthalpie von AHsub = 148,4 kcal/mol und der Schmelzwarme von 19,4 kcal/mol. Die zugehorige Gleichung fur das flussige U 0 2 wurde bestimmt zu logp(atm) = 7,7 -27900/T mit einer Verdampfungsenthalpie AHverd = 127,6 kcal/mol, ebenfalls in Ubereinstimmung mit friiheren Messungen unterhalb des Schmelzpunktes von AH,,, = 144,l kcal/mol und der Schmelzwarme von 17,7 kcal/mol. Fur diese Messungen wurde eine neue Laseraufheiztechnik entwickelt, die eine Temperaturaufzeichnung in Mikrosekundenbereich einschlieBt. Erste quantitative Messungen am (U, Pu)02 oberhalb 4000 K wurden anlaI3lich des ,,IAEA Symposium on Thermodynamics of Nuclear Materials" in Wien vorgestellt. Die Untersuchung des gesamten Temperaturbereiches von T = 3000 K bis Tkri, = 7560 K zeigt zwei prinzipie...

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High‐temperature mass spectrometric study of thermodynamic properties in the UO₂–ZrO₂ system

Stolyarova

Vorozhtcov

Kurata

et al. 2020

Rapid Comm Mass Spectrometry

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Rationale The UO2–ZrO2 solid solution at high temperatures is the key system of modern nuclear science and technology in the context of the safety operation of nuclear cycles, the consequences of severe accidents, and the incorporation of nuclear waste. Urgent needs of the continuation of experimental studies of this system at temperatures up to 3000 K are aimed at preventing severe accidents similar to Chernobyl and Fukushima when the thermodynamic approach is used for the prediction of high‐temperature behavior of materials. Methods This investigation was carried out using the Knudsen effusion mass spectrometric method using the MS‐1301 magnetic sector mass spectrometer. The samples in the UO2–ZrO2 system were vaporized from a tungsten effusion cell. Vapor species effusing from the cell were ionized at an electron ionization energy of 70 eV. Results The vaporization and thermodynamics of pure UO2 and ZrO2 as well as of the samples in the UO2–ZrO2 system were studied in the range 2000–2730 K. The temperature dependences of the partial vapor pressures of UO and UO2 over pure UO2 were obtained at 2060–2456 K, which agreed with the literature results. The partial vapor pressures of UO, UO2, ZrO, and ZrO2, the vaporization rates, and the UO2 and ZrO2 activities in the UO2–ZrO2 solid solutions were determined at 2370, 2490, 2570, and 2730 K. Conclusions The component activities and excess Gibbs energies of the UO2–ZrO2 system indicated a change in deviations from the ideal behavior from positive to negative with the temperature increase from 2370 to 2730 K. The thermodynamic functions of formation from the oxides of the solid solutions in the UO2–ZrO2 system such as Gibbs energies as well as the enthalpies and entropies of formation were obtained for the first time at 2550 K in the composition range 0.89–1.00 ZrO2 mole fraction.

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Total pressure of uranium-bearing species over molten urania

Cited by 33 publications

References 6 publications

Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

Vapour Pressure Studies Over Liquid Uranium Oxide and Uranium Plutonium Oxide Up to 5000 K

High‐temperature mass spectrometric study of thermodynamic properties in the UO₂–ZrO₂ system

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Total pressure of uranium-bearing species over molten urania

Cited by 33 publications

References 6 publications

Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

Vapour Pressure Studies Over Liquid Uranium Oxide and Uranium Plutonium Oxide Up to 5000 K

High‐temperature mass spectrometric study of thermodynamic properties in the UO2–ZrO2 system

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High‐temperature mass spectrometric study of thermodynamic properties in the UO₂–ZrO₂ system