Thermal Expansion of a Simulated Fuel with Fission Products Forming Solid Solutions

Thermal expansions of UO₂ and a simulated fuel with fission products forming a solid solution were studied using a dilatometer in the temperature range from 298 to 1800 K. The densities of the UO₂ and the simulated fuel used in the measurements were 10.43 g · cm⁻³ (95.2% of theoretical density (TD)) and 10.35 g · cm⁻³ (95.6% of TD), respectively. The linear thermal expansion of the simulated fuel is higher than that of UO₂, and the difference between this fuel and UO₂ increases monotonically with temperature. The average linear thermal expansion coefficients of UO₂ and the simulated fuel are 1.09× 10⁻⁵ and 1.23×10⁻⁵ K⁻¹, respectively. As the temperature increases to 1800 K, the relative densities of UO₂ and the simulated fuel decrease to 95.1 and 94.7% of their initial densities at 298 K.Paper presented at the Seventh Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui, P. R. China.     

Thermal Expansion of Simulated Fuels with Dissolved Fission Products in a UO2 Matrix

As a part of the DUPIC (direct use of spent PWR fuel in CANDU reactors) fuel development program, the thermal expansion of simulated spent fuel pellets with dissolved fission products has been studied by using a thermo-mechanical analyzer (TMA) in the temperature range from 298 K to 1773 K to investigate the effects of fission products forming solid solutions in a UO₂ matrix on the thermal expansions. Simulated fuels with an equivalent burn-up of (30 to 120) GWd/tU were used in this study. The linear thermal expansions of the simulated fuel pellets were higher than that of UO₂, and the difference between these fuel pellets and UO₂ increased monotonically with temperature. For the temperature range from 298 K to 1773 K, the values of the average linear thermal expansion coefficients for UO₂ and simulated fuels with an equivalent burn-up of (30, 60, and 120) GWd/tU are 1.19 × 10⁻⁵ K⁻¹, 1.22 × 10⁻⁵ K⁻¹, 1.26 × 10⁻⁵ K⁻¹, and 1.32 × 10⁻⁵ K⁻¹, respectively.     

Thermal Conductivity of a Simulated Fuel with Dissolved Fission Products

The thermal diffusivity of a simulated fuel with fission products forming a solid solution was measured using the laser-flash method in the temperature range from room temperature to 1673 K. The density and the grain size of the simulated fuel with the solid solutions used in the measurement were 10.49 g · cm⁻³ (96.9% of theoretical density) at room temperature and 9.5 μm, respectively. The diameter and thickness of the specimens were 10 and 1 mm, respectively. The thermal diffusivity decreased from 2.108 m² · s⁻¹ at room temperature to 0.626 m² · s⁻¹ at 1673 K. The thermal conductivity was calculated by combining the thermal diffusivity with the specific heat and density. The thermal conductivity of the simulated fuel with the dissolved fission products decreased from 4.973 W · m⁻¹ · K⁻¹ at 300 K to 2.02 W · m⁻¹ · K⁻¹ at 1673 K. The thermal conductivity of the simulated fuel was lower than that of UO₂ by 34.36% at 300 K and by 15.05% at 1673 K. The difference in the thermal conductivity between the simulated fuel and UO₂ was large at room temperature, and decreased with an increase in temperature. Paper presented at the Seventeenth European Conference on Thermophysical Properties, September 5–8, 2005, Bratislava, Slovak Republic.     

Deviation from Wiedemann–Franz Law for the Thermal Conductivity of Liquid Tin and Lead at Elevated Temperature

The thermal conductivities of tin and lead in solid and liquid states have been determined using a nonstationary hot wire method. Measurements on tin and lead were carried out over temperature ranges of 293 to 1473 K and 293 to 1373 K, respectively. The thermal conductivity of solid tin is 63.9±1.3 Wm^–1K^–1 at 293 K and decreases with an increase in temperature, with a value of 56.6±0.9 Wm^–1K^–1 at 473 K. For solid lead, the thermal conductivity is 36.1±0.6 Wm^–1K^–1 at 293 K, decreases with an increase in temperature, and has a value of 29.1±1.1 Wm^–1K^–1 at 573 K. The temperature dependences for solid tin and lead are in good agreement with those estimated from the Wiedemann–Franz law using electrical conductivity values. The thermal conductivities of liquid tin displayed a value of 25.7±1.0 Wm^–1K^–1 at 573 K, and then increased, showing a maximum value of about 30.1 Wm^–1K^–1 at 673 K. Subsequently, the thermal conductivities gradually decreased with increasing temperature and the thermal conductivity was 10.1±1.0 Wm^–1K^–1 at 1473 K. In the case of liquid lead, the same tendency, as was the case of tin, was observed. The thermal conductivities of liquid lead displayed a value of 15.4±1.2 Wm^–1K^–1 at 673 K, with a maximum value of about 15.6 Wm^–1K^–1 at 773 K and a minimum value of about 11.4±0.6 Wm^–1K^–1 at 1373 K. The temperature dependence of thermal conductivity values in both liquids is discussed from the viewpoint of the Wiedemann–Franz law. The thermal conductivities for Group 14 elements at each temperature were compared.     

Thermophysical Property Measurements of Supercooled and Liquid Rhodium

The density, the isobaric heat capacity, the surface tension, and the viscosity of liquid rhodium were measured over wide temperature ranges, including the supercooled phase, using an electrostatic levitation furnace. Over the 1820 to 2250 K temperature span, the density can be expressed as (T)=10.82×10³–0.76(T–T _m ) (kgm^–3) with T _m =2236 K, yielding a volume expansion coefficient (T)=7.0×10^–5 (K^–1). The isobaric heat capacity can be estimated as C _P (T)=32.2+1.4×10^–3(T–T _m ) (Jmol^–1K^–1) if the hemispherical total emissivity of the liquid remains constant at 0.18 over the 1820 to 2250 K interval. The enthalpy and entropy of fusion have also been measured, respectively, as 23.0 kJmol^–1 and 10.3 Jmol^–1K^–1. In addition, the surface tension can be expressed as (T)=1.94×10³–0.30(T–T _m ) (mNm^–1) and the viscosity as (T)=0.09 exp[6.4×10⁴(RT)] (mPas) over the 1860 to 2380 K temperature range.     

Synthesis,structure, and physicochemical properties of compounds Pb(B<Superscript>V</Superscript>UO<Subscript>6</Subscript>)<Subscript>2</Subscript> ⋅ <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (B<Superscript>V</Superscript> = P,As, V)

Compounds Pb(B^VUO₆)₂ nH₂O (B^V = P, As, V) were synthesized and studied by X-ray diffraction, IR spectroscopy, thermal analysis, and reaction calorimetry. The standard enthalpies and Gibbs energies of formation of the compounds at T = 298 K were determined, and processes involving these compounds were quantitatively characterized.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 412–417.Original Russian Text Copyright © 2004 by Suleimanov, Chernorukov, Golubev.     

Non-Contact Measurements of the Thermophysical Properties of Hafnium-3 Mass% Zirconium at High Temperature

Several thermophysical properties of hafnium-3 mass % zirconium, namely the density, the thermal expansion coefficient, the constant pressure heat capacity, the hemispherical total emissivity, the surface tension and the viscosity are reported. These properties were measured over wide temperature ranges, including overheated and undercooled states, using an electrostatic levitation furnace developed by the National Space Development Agency of Japan. Over the 2220 to 2875 K temperature span, the density of the liquid can be expressed as _L (T)=1.20×10⁴–0.44(T–T _m ) (kgm^–3) with T _m =2504 K, yielding a volume expansion coefficient _L (T)=3.7×10^–5 (K^–1). Similarly, over the 1950 to 2500 K span, the density of the high temperature and undercooled solid -phase can be fitted as _S (T)=1.22×10⁴–0.41(T–T _m ), giving a volume expansion coefficient _S (T)=3.4×10^–5. The constant pressure heat capacity of the liquid phase can be estimated as C _PL (T)=33.47+7.92×10^–4(T–T _m ) (Jmol^–1K^–1) if the hemispherical total emissivity of the liquid phase remains constant at 0.25 over the 2250 K to 2650 K temperature interval. Over the 1850 to 2500 K temperature span, the hemispherical total emissivity of the solid -phase can be represented as _TS (T)=0.32+4.79×10^–5(T–T _m ). The latent heat of fusion has also been measured as 15.1 kJmol^–1. In addition, the surface tension can be expressed as (T)=1.614×10³–0.100(T–T _m ) (mNm^–1) and the viscosity as h(T)=0.495 exp [48.65×10³/(RT)] (mPas) over the 2220 to 2675 K temperature range.     

Density Determination of Liquid Copper, Nickel, and Their Alloys

A method for the determination of the density of electromagnetically levitated metallic liquids has been developed. This method employs an enlarged beam of parallel laser light to produce a shadow image of the sample. The shadow is recorded by a digital CCD-camera, and the images are analyzed using an edge detection algorithm. The circumference is fitted by Legendre polynomials that can be used for calculations of the volume of the sample. The method has been tested successfully on various alloys of copper-nickel (Ni _x Cu _y ), as well as on the pure elements, Cu and Ni. Densities were measured for each sample at different temperatures below and above the melting point, and a linear behavior was observed. At the melting point the densities for copper and nickel were 7.9 and 7.93gcm^–3, respectively. For T=1270°C liquid copper has a density of 7.75gcm^–3 which strongly increases up to roughly 8.1gcm^–3 if a small amount (10–40 at.%) of nickel is added to the system. For nickel concentrations larger than 50at.% the density remains nearly constant.     

Solubility of tributyl phosphate and its degradation products in concentrated uranyl nitrate solutions and of uranyl nitrate in tributyl phosphate at elevated temperatures

Solubility of UO₂(NO₃)₂, TBP, and its degradation products in the organic and aqueous phases of the system TPB-H₂O-HNO₃-UO₂(NO₃)₂ at 25–128°C over the uranyl nitrate concentration range 200–1200 g 1^–1 is studied. The solubility of TBP and its degradation products in uranyl nitrate hexahydrate melt decreases in the order H₂MBP > HDBP > TBP > H₃PO₄. At the boiling point of the melt, their solubility ranges from 100 to 0.5 g l^–1. The solubility of uranyl nitrate in the TBP phase under the same conditions is caused by formation of complexes with a composition close to that of the monosolvate UO₂(NO₃) ₂ TBP.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 436–439.Original Russian Text Copyright © 2004 by Usachev, Markov.     

Compressed Liquid and Supercritical Densities of 1,1,1,2,3,3,3-Heptafluoropropane (R227ea)

Densities of 1,1,1,2,3,3,3-heptafluoropropane (R227ea) have been measured with a computer-controlled high-temperature high-pressure vibrating-tube densimeter system (DMA-HDT) in the sub- and supercritical states. The densities were measured at temperatures from 278 to 473 K and pressures up to 30 MPa (overall 257 data points), whereby a density range between 285 and 1588 kgm^–3 was covered. The uncertainty in the density measurement was estimated to be better than ±0.2 kgm^–3. The experimental data of R227ea were correlated with a virial-type equation of state (EoS) and compared with published data. A comparison is also made with a recent wide-range dedicated equation of state for R227ea.     

Isochoric Heat Capacity Measurements for 0.5 H2O+0.5 D2O Mixture in the Critical Region

The isochoric heat capacity C _V of an equimolar H₂O+D₂O mixture was measured in the temperature range from 391 to 655 K, at near-critical liquid and vapor densities between 274.05 and 385.36 kgm^–3. A high-temperature, high-pressure, nearly constant-volume adiabatic calorimeter was used. The measurements were performed in the one- and two-phase regions including the coexistence curve. The uncertainty of the heat-capacity measurement is estimated to be ±2%. The liquid and vapor one- and two-phase isochoric heat capacities, temperatures, and densities at saturation were extracted from the experimental data for each measured isochore. The critical temperature and the critical density for the equimolar H₂O+D₂O mixture were obtained from isochoric heat capacity measurements using the method of quasi-static thermograms. The measurements were compared with a crossover equation of state for H₂O+D₂O mixtures. The near-critical isochoric heat capacity behavior for the 0.5 H₂O+0.5 D₂O mixture was studied using the principle of isomorphism of critical phenomena. The experimental isochoric heat capacity data for the 0.5 H₂O+0.5 D₂O mixture exhibit a weak singularity, like that of both pure components. The reliability of the experimental method was confirmed with measurements on pure light water, for which the isochoric heat capacity was measured on the critical isochore (321.96 kgm^–3) in both the one- and two-phase regions. The result for the phase-transition temperature (the critical temperature, T _{C, this work}=647.104±0.003 K) agreed, within experimental uncertainty, with the critical temperature (T _{C, IAPWS}=647.096 K) adopted by IAPWS.     

Sorption of cesium iodide radioactive aerosols on metal felt during oxidative hydrolysis in steam gas-system

The behavior of ¹³⁷Cs ¹³¹I radioactive aerosols at sorption in a column packed with Bekipor WB metal felt from argon, air, and steam-gas flow was studied to assess the possibility of formation of CsI CsOH and CsI₃ in the course of CsI oxidative hydrolysis. The layer distribution of radionuclides in the column was analyzed as influenced by temperature (405–560 K), carrier gas humidity (up to 60 vol %), flow velocity (2–6 cm s¹), and amount of cesium iodide sorbed on the felt (0.7–65.0 mg). It was found that the oxidative hydrolysis under certain conditions yields CsI CsOH and CsI₃ aerosols. Although under the experimental conditions studied the sorption of radionuclides on the metal felt is nearly quantitative (97–99%), escape of the radionuclides from the column upon prolonged passing of steam-gas mixtures cannot be excluded.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 449–453.Original Russian Text Copyright © 2004 by Kulyukhin, Mikheev, Kamenskaya, Rumer, Konovalova, Novichenko.     

Thermal Conductivity of Simulated Fuels with Dissolved Fission Products

The thermal diffusivity of simulated fuels with dissolved fission products was measured by using the laser-flash method in the temperature range from room temperature to 1,473 K. Three kinds of simulated fuels with an equivalent burn-up of 3, 6, and 12 at% were used in the measurement. The thermal diffusivity and the thermal conductivity of the simulated fuels with the dissolved fission products decreased, as the temperature and the equivalent burn-up increased. The thermal conductivities of simulated fuels with equivalent burn-ups of 3, 6, and 12 at% were lower than that of UO₂ by 84.70, 67.17, and 44.97% at 300 K and 99.17, 89.88, and 80.56% of UO₂ at 1,473 K, respectively. The difference in the thermal conductivity between the simulated fuel and UO₂ was large at room temperature, and it decreased as the temperature increased. The thermal resistivity of the simulated fuels increased linearly with temperature up to 1,473 K.     

The Density of UO2–ZrO2 Alloys

The density of a UO₂–ZrO₂ melt (atomic ratio U/Zr = 1.528) is experimentally measured by a pycnometric method in the temperature range of 2973–3373 K. The found temperature dependence of density has the form (T) = (7.0 ± 0.01) – (4.5 ± 0.4) × 10^–4 × (T – 2973 K), g/cm³. The temperature dependence measured enables one to calculate the values of the density of UO₂–ZrO₂ melts depending on the temperature and composition for any atomic ratio U/Zr.     

Measurement of the Surface Tension of Undercooled Liquid Ti90Al6V4 by the Oscillating Drop Technique

The surface tension of liquid Ti₉₀Al₆V₄ was measured. The samples have been processed containerlessly by electromagnetic levitation, which allows the handling of highly reactive materials and measurements in the undercooled temperature region. The use of digital image processing allows the identification of oscillation modes and calculation of the surface tension from the l = 2 and m = 0, m = 2 oscillation modes. A linear least squares fit to the data showed the following temperature dependence: = 1.389 ± 0.09 – 9.017 × 10^–4 ± 5.64 × 10^–5(T – 1660°C) [Nm^–1]     

Surface Tension and Density of Oxygen-Free Liquid Aluminum at High Temperature

New values of densities and surface tensions of liquid aluminum obtained in the range 1600 to 2360 K by contactless techniques in neutral gases are reported. Conditions for oxygen-free aluminum are fulfilled which allow determination of the surface tension of aluminum. Extrapolation to the melting point, T _m = 933 K, confirms the value of (T = 933K) = 1.05 N m^–1.     

System ZnO ⋅ B<Subscript>2</Subscript>O<Subscript>3</Subscript>-CuO ⋅ B<Subscript>2</Subscript>O<Subscript>3</Subscript>

Differential thermal analysis and x-ray diffraction data indicate that the ZnO B₂O₃-CuO B₂O₃ join of the ternary system CuO-B₂O₃-ZnO is pseudobinary, with eutectic phase relations and a liquid-liquid miscibility gap in the composition range 25–35 mol % CuO.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 339–340.Original Russian Text Copyright © 2005 by Kasumova, Bananyarly.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Measurement of the enthalpy and specific heat of a Be2C-graphite-UC2 reactor fuel material to 1980 K

The enthalpy and specific heat of a Be₂C-Graphite-UC₂ composite nuclear fuel material have been measured over the temperature range 298–1980 K using both differential scanning calorimetry and liquid argon vaporization calorimetry. The fuel material measured was developed at Sandia National Laboratories for use in pulsed test reactors. The material is a hot-pressed composite consisting of 40 vol% Be₂C, 49.5 vol% graphite, 3.5 vol% UC₂, and 7.0 vol% void. The specific heat was measured with the differential scanning calorimeter over the temperature range 298–950 K, while the enthalpy was measured over the range 1185–1980 K with the liquid argon vaporization calorimeter. The normal spectral emittance at a wavelength of 6.5×10^–5 cm was also measured over the experimental temperature range. The combined experimental enthalpy data were fit using a spline routine and differentiated to give the specific heat. Comparison of the measured specific heat of the composite to the specific heat calculated by summing the contributions of the individual components indicates that the specific heat of the Be₂C component differs significantly from literature values and is approximately 0.56 cal · g^–1 · K ^–1 (2.3×10³J · kg^–1 · K ^–1) for temperatures above 1000 K.     

Thermodynamic functions of Americium metal

A critical analysis of the data for the specific heat from 15 K to 300 K of two samples of ²⁴¹Am and one sample of ²⁴³Am leads to a set of best values. From these the thermodynamic functions are calculated, giving (C _p)₂₉₈ = 25.5 ± 1 J mol^–1 K^–1 and S ₂₉₈ = 55.4 ± 2 J mol^–1 K^–1. The derived Debye characteristic temperature _D is estimated as 120 ± 20 K and the electronic specific heat coefficient as 1 ± 1 mJ mol^–1 K^–2.     

Electron-Phonon Coupling in Bolometers Used for Cryogenic Particle Detection

Superconducting transition-edge sensors have been used extensively in cryogenic particle detectors, either as thermometers for microcalorimetry or as bolometers for the detection of the prompt phonons resulting from a particle decay in a single crystal absorber. Bolometer action depends upon the energy coupling of the prompt phonons to the bolometer electrons. A study has been made of the electron-phonon coupling for a series of Au-Ti bolometers on a Si substrate and of the use of these bolometers for prompt phonon detection below 1 K. The electron-phonon coupling was found to be proportional to the normalized resistance (R/R _n) of the bolometer; R is the bolometer resistance and R _n is the normal resistance. When extrapolated to R/R _n = 1, this coupling was consistent with /VT ³ = 3 × 10⁹ Wm^–3K^–4 where is the thermal conductance from the bolometer electrons to the Si phonons and V and T are the volume and transition temperature of the bolometer. The response of the bolometers to heat pulses generated by a thin film heater on the opposite face of a Si single crystal were similar to that generally seen above 1 K, apart from a delay time constant that varied from 0.5 to 1.3 µs as the transition temperature decreased from 600 to 200 mK. This delay time constant is attributed to the thermal equilibrium time of normal regions of the bolometer.