Analysis of blowdown experiment of 110 scale steam generator model

A subcooled blowdown experiment in a $\text{1}\text{10}$ scale steam generator (SG) model is analyzed by the use of a fluid-structure computer code (MULTIFLEX). The experimental model simulates the secondary side of a SG with a preheater. The MULTIFLEX code that solves simultaneously a coupled set of one-dimensional hydraulic conservation equations and structural dynamic equations is used to analyze the experiment, taking into account the fluid structure interaction between the secondary coolant and the SG structure, the baffle and tube support plates and the divider plate. The computed values of pressure and wall displacement histories agree well with the experimental data. The success of the analysis supports the use of the one-dimensional MULTIFLEX code to analyses of thermal hydraulic transients in the SG secondary side and the validity of the method for modeling the complicated system of the fluid-structure interactions.     

Electron capture from atomic hydrogen in the keVamu energy range

The results of molecular calculations for electron capture from hydrogen by a number of fully stripped projectiles and projectiles with a 1s² core are reported and compared with theoretical and experimental values from the literature     

Structural response of 120-scale models of the CRBR to a simulated HCDA

The structural integrity of scale models of the Clinch River Breeder Reactor (CRBR) vessel and head under a simulated hypothetical core disruptive accident (661 MWs) is evaluated experimentally. Tests of three $\text{1}\text{20}\text{-}\text{scale}$ models of the CRBR, each of increasing complexity, showed the effects of the upper internals structure (UIS), a thermal liner, and other structural details on vessel and head response. A fourth model, identical to the most complex model but with more instrumentation, demonstrated experimental reproducibility. Ni 200 simulated 304 SS, the material used to fabricate the full-scale vessel wall, core barrel, and core support platform; water simulated liquid sodium; and the detonation products of a low-density explosive simulated the HCDA core loads. Loading pressures, strains, and accelerations were measured.     

Precision X-ray spectroscopy on 8.5 MeVamu heavy ions

A new experimental capability has been developed at the Lawrence Berkeley Laboratory Super-HILAC to investigate questions relating to high resolution atomic spectroscopy. A key element of these measurements is a dual arm Johann spectrometer. The ion beam passes inside the Rowland circle of two curved crystals which are mounted such that diffracted X-rays have equal and opposite linear Doppler shifts. The X-ray lines are detected with high speed X-ray film mounted on the Rowland circle. The beam-crystal geometry is arranged so a spectral range θ_B ~ 30°–70° is detected. The spectrometer efficiency is high with useful exposures obtained with only 10 mC of beam. A wavelength calibration is obtained by simultaneously exposing the film with diffracted K and L X-rays from an X-ray tube. X-ray lines from the beam are slanted, with respect to the calibration lines, due to Doppler shifts arising from X-rays incident on the crystal at angles other than perpendicular to the diffraction plane. The slope of these lines provides an independent determination of the beam velocity, which is used to correct for the transverse Doppler shift. Typical results are presented.     

〈c〉-Component dislocations in zirconium alloys

Dislocations with $\text{〈c〉-}\text{component}$ Burgers vectors have been found in abundance near deformation twins, and to a lesser extent near grain boundary junctions, in deformed Zircaloy-2 and Zircaloy-4. Both pure $\text{〈c〉}$ and $\text{〈c + a〉}$ dislocations have been identified by TEM contrast experiments. The segments of $\text{〈c〉-}\text{component}$ dislocations tend to be long, straight, and to lie on either basal or pyramidal planes. It is suggested that these dislocations are generated in order to maintain compatibility between crystallites which differ significantly in their ability to accommodate an imposed deformation by $\text{〈a〉-}\text{slip}$. The manner in which $\text{〈c〉-}\text{component}$ dislocations can alter the partitioning of irradiation-produced point defects, and their influence on irradiation growth are discussed.     

Stopping cross sections and backscattering factors for 4He ions in matter Z = 1–92, E(4He) = 400–4000 keV

A table is presented of semiempirical values of stopping cross sections [expressed in eV/(atom/cm²)] for ⁴He ions in every element (1 ≤ Z ≤ 92) for ion energies from 400 to 4000 keV. The semiempirical results have been fitted with polynomial expansions whose coefficients are also tabulated. The stopping cross sections provide parameters for the interpretation of backscattering experiments, for example factors for converting backscattering-peak widths to areal density (atoms/cm²). The semiempirical results are based on recent experimental measurements and on theoretical values calculated in the Lindhard-Winther formalism with Hartree-Fock-Slater elemental wavefunctions. Comments are included on combining the specific energy loss tables for compound backscattering analysis by using Bragg's Rule, and also on the effects on backscattering of target tilt and of the finite thicknesses of targets.     

Investigations on UAlx-Al dispersion fuels for high-flux reactors

The paper outlines the preparation of $\text{UAl}{}_{\mathrm{x}}\text{-Al}$ dispersion fuel plates for thermal high-flux reactors. The work described includes the preparation of UAl₂, UAl₃ and UAl₄ compounds by induction melting and their processing to Al-clad fuel plates using the picture-frame technique. Induction melting in alumina crucibles and subsequent homogenisation can be used to produce relatively homogeneous $\text{UAl}{}_{\mathrm{x}}$ compounds. After comminution to a predetermined size range and blending with Al, the pressed compacts can be rolled into Al-clad fuel plates. UAl₃ and UAl₂ compounds react with Al forming UAl₄. The reactions begin at about 673 K, and have an activation energy of 52.6 and 42.6 kcal/mol, respectively. The measured properties of the dispersions and UAl-phases such as thermal expansion, thermal and electrical conductivity, tensile strength, microhardness and hot hardness are affected by the concentration of the dispersed phase and can be explained in the light of existing theoretical models. Due to its potential as a high-flux reactor fuel with higher uranium content the preparation and properties of UAl₂-Al dispersions as well as the preliminary data about their stability under irradiation may be of particular interest.     

Parametric determination of a Si(Li) detector efficiency curve using KβKα branching ratios

The efficiency curve of a Si(Li) detector was determined with the parametric model of Gallagher and Cipolla which considers the parameters to be free, being determined by a least-squares fit to experimentally measured points. A least-squares fit can strongly correlate the physically uncorrelated parameters. In this paper, we do an energy analysis of the parametric expression and we propose a method to calculate the low energy parameters independently of those of the high energy region.     

Oxygen diffusion measurements in porous UO2 + x

The ion microprobe mass analyzer was used to measure oxygen diffusivity in porous hyperstoichiometric uranium dioxide. The effect of porosity on diffusivity is discussed in terms of percolation theory. The limited data reported herein indicate a diffusivity threshold when the volume fraction of pores is 0̃.3. At this porosity, the oxygen diffusion changes from solid-like to gas-like behavior.     

Phase relation and defect structures of nonstoichiometric U4O9±y and UO2+x at high temperatures

Phase relations in the composition range from $\text{UO}{}_{\mathrm{2+x}}$ to $\text{U}{}_3\text{O}{}_{\mathrm{8?z}}$ were studied by electrical-conductivity measurements and X-ray diffraction in the ranges $\text{1025°C ? T ? 1140°C}$ and . The plot of log σ versus log showed straight lines with distinct slopes, which corresponded to four regions ($\text{UO}{}_{\mathrm{2+x}}$, $\text{U}{}_4\text{O}{}_{\mathrm{9?y}}$, $\text{U}{}_4\text{O}{}_{\mathrm{9+y}}$ and $\text{U}{}_3\text{O}{}_{\mathrm{8?z}}$). The existence of the hyperstoichiometric $\text{U}{}_4\text{O}{}_{\mathrm{9+y}}$ phase was suggested in the temperature range from 1025 to 1126°C. The peritectoid temperature ($\text{U}{}_4\text{O}{}_{\mathrm{9\pm y}}\text{= UO}{}_{\mathrm{2+x}}\text{+ U}{}_3\text{O}{}_{\mathrm{8?z}}$) was estimated to be present between 1126 and 1131°C. The partial free enthalpies and entropies for the two-phase equilibrium ($\text{U}{}_4\text{O}{}_{\mathrm{9+y}}\text{+ U}{}_3\text{O}{}_{\mathrm{8?z}}$, and $\text{U}{}_4\text{O}{}_{\mathrm{9?y}}\text{+ UO}{}_{\mathrm{2+x}}$) were calculated and compared with previous results. From the dependence of the electrical conductivity on the oxygen partial pressure the nonstoichiometric defect structures of $\text{UO}{}_{\mathrm{2+x}}$ and $\text{U}{}_4\text{O}{}_{\mathrm{9\pm y}}$ were interpreted as consisting of doubly charged oxygen interstitials (O_i'') and doubly charged oxygen vacancies (V_O''). At room temperature, the homogeneity range of the U₄O₉ phase was investigated with a Debye-Scherrer camera.     

Sublimation thermodynamics of UO2 − x

The uranium activity has been measured between 1667 and 2175 K, and between $\text{U}\text{(l) +}\text{UO}{}_{\mathrm{2\; ?\; x}}$ and UO_2.0 using a mass spectrometer to study the behavior of UO(g). Equations are presented which allow the pressure of the vapor species to be calculated as a function of temperature and composition. The composition variation of activity agrees well with the average of the results from previous activity measurements, but the variation in the measured enthalpy of vaporization is in direct conflict.     

The average number of prompt neutrons v̄p, from neutron induced fission of 235U between 0.2 and 1.4 MeV

For the clarification of existing discrepancies in the energy dependence of $\text{v}\text{?}{}_{\mathrm{p}}$ for ²³⁵U an experiment was performed which was based on a method independent of current techniques. A considerable reduction of background and correction problems was achieved by renouncing on an absolute measurement. Thus the resulting systematic uncertainty was 0·6%. In the energy range between 0·2 and 1·4 MeV the shape of $\text{v}\text{?}{}_{\mathrm{p}}$ was measured at 22 points in steps of 50 keV with an average energy resolution of 3·3%. Repetition of several runs with modified experimental conditions ensured the consistent reproduction of the results. It was found that $\text{v}\text{?}{}_{\mathrm{p}}$ of ²³⁵U shows distinct deviations of up to 2% from a linear energy dependence.     

Ionization of He,Ne and Ar atoms by 1.05 MeVamuCq+(q = 2–6) and Arq+(q = 4–14) ion impact

Total “apparent” ionization cross sections and partial cross section of the production of highly ionized recoil ions of He, Ne and Ar in 1.05 MeV/amu highly charged C^q+(q = 2–6) and Ar^q+(q = 4,6,10–14) ion impact have been measured and compared with theoretical prediction and other experimental data. The total ionization cross sections have been found to scale as the square of the effective charge of projectile ions $\text{q}{}^1$, as predicted by theories.     

Equilibrium oxygen partial pressure and phase diagram of the uranium-oxygen system in the composition range 2.61 < o/u < 2.67 between 844 and 1371 K

The equilibrium partial pressure of oxygen in the uranium-oxygen system has been determined by a thermogravimetric technique in the composition range $\text{2.61 < O/U < 2.67}$ and for temperatures between 800 and 1400 K. The nature of the uranium-oxygen phase diagram in this composition and temperature range has been established from the results obtained.The nearly stoichiometric phase $\text{U}{}_3\text{O}{}_{\mathrm{8\; \pm \; z}}$ has been confirmed to exist in the U-O system, together with a nonstoichiometric $\text{U}{}_8\text{O}{}_{\mathrm{21\; \pm \; x}}$ phase which is stable in the range $\text{2.617 < O/U < 2.655}$. The high precision of the experimental set up has permitted the determination of the narrow two phase region ($\text{U}{}_3\text{O}{}_{\mathrm{8?z}}\text{+ U}{}_8\text{O}{}_{\mathrm{21\; +\; x}}$) with small errors.A hysteresis has been observed in the versus O/U ratio. The corresponding metastable states could have been obtained only upon oxidation of the $\text{U}{}_8\text{O}{}_{\mathrm{21\; \pm \; x}}$ phase. These metastable states have been observed to depend on sample morphology.The partial molar enthalpy and entropy of solution of oxygen in the $\text{U}{}_8\text{O}{}_{\mathrm{21\; \pm \; x}}$ phase have also been evaluated.     

Neutron production cross sections and energies for the reactions 7Li(p,n)7Be and 7Li(p,n)7Be1

Center-of-mass best values for the normalized Legendre coefficients and the 0° differential cross sections as functions of input energy have been derived from various experimental results for the reactions ⁷Li(p,n)⁷Be and ${}^7\text{Li}\text{(p,n)}{}^7\text{Be}{}^1$ (431 keV). This information has been used to calculate laboratory differential cross sections as functions of the laboratory proton energy and neutron emission angle which are given in tabular form together with the corresponding neutron energies.     

Transport properties of U0.7Ce0.3O2 − x

We have determined a number of transport properties of $\text{U}{}_{0.7}\text{Ce}{}_{0.3}\text{O}{}_{\mathrm{2-x}}$ at 1273 K for various deviations from stoichiometry and compared them with available results on $\text{(UPu)O}{}_{\mathrm{2\; ?\; x}}$. They are: the electrical conductivity, Seebeck coefficient, effective charge number and chemical diffusion coefficient.A very characteristic behaviour is observed for the electronic properties of $\text{(UCe)O}{}_{\mathrm{2\; ?\; x}}$. A p-type conduction for all the studied deviations from stoichiometry (up to $\text{x = 3 × 10}{}^{\mathrm{?2}}$) is interpreted in terms of a high electronic disorder in the stoichiometric compound. Electronic disorder at stoichiometry is probably less important in $\text{(UPu)O}{}_{\mathrm{2\; ?\; x}}$, which presents a sharp p-n transition at $\text{x = 5 × 10}{}^{\mathrm{?3}}$.Ionic transport properties obtained on $\text{(UCe)O}{}_{\mathrm{2\; ?\; x}}$ indicate an approximate proportionality between the ionic conductivity resulting from oxygen ions transport and the deviation from stoichiometry. Results available on $\text{(UPu)O}{}_{\mathrm{2\; ?\; x}}$ do not appear to be compatible with ours and some arguments are presented which cast doubt on their validity.     

Photoionization and photoabsorption cross sections of He, O,N2 and O2 for aeronomic calculations

A compilation of experimental and theoretical photoionization and photoabsorption cross sections is presented for He, O, N₂, and O₂ for use in studies of ion and photoelectron production in the terrestrial ionosphere. In wavelength regions where rapid variations occur in the cross sections, averaged cross sections are calculated. When necessary the cross sections have been extrapolated to shorter wavelengths. The cross sections are tabulated at the wavelengths of the solar lines and continua given in the solar reference spectrum of Hinteregger from ～1030 to ～34 Å. For the molecules N₂ and O₂, branching ratios are given for ionization into the ground and electronic states of the molecular ions and for dissociative ionization.