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Neutron resonance absorption imaging is a non-destructive technique that can characterize the elemental composition of a sample by measuring nuclear resonances in the spectrum of a transmitted beam. Recent developments in pixelated time-of-flight imaging detectors coupled with pulsed neutron sources pose new opportunities for energy-resolved imaging. In this paper we demonstrate non-contact measurements of the partial pressure of xenon and krypton gases encapsulated in a steel pipe while simultaneously passing the neutron beam through high-Z materials. The configuration was chosen as a proof of principle demonstration of the potential to make non-destructive measurement of gas composition in nuclear fuel rods. The pressure measured from neutron transmission spectra (∼739 ± 98 kPa and ∼751 ± 154 kPa for two Xe resonances) is in relatively good agreement with the pressure value of ∼758 ± 21 kPa measured by a pressure gauge. This type of imaging has been performed previously for solids with a spatial resolution of ∼ 100 μm. In the present study it is demonstrated that the high penetration capability of epithermal neutrons enables quantitative mapping of gases encapsulate within high-Z materials such as steel, tungsten, urania and others. This technique may be beneficial for the non-destructive testing of bulk composition of objects (such as spent nuclear fuel assemblies and others) containing various elements opaque to other more conventional imaging techniques. The ability to image the gaseous substances concealed within solid materials also allows non-destructive leak testing of various containers and ultimately measurement of gas partial pressures with sub-mm spatial resolution. [ABSTRACT FROM AUTHOR]

U3Si has the highest uranium density of the U-Si compounds, making it an attractive option for specialized reactor applications. Although the compound has been used in research and test reactors for nearly six decades, little data has been published in the literature which characterizes the thermophysical properties at elevated temperatures. A systematic study was conducted on U3Si to characterize thermal expansion, heat capacity, thermal diffusivity, and thermal conductivity as a function of temperature to 1150 K. Thermophysical properties were also tabulated for the high temperature δ'-U3Si phase as a function of temperature, which has not been reported previously. [ABSTRACT FROM AUTHOR]

Electron beam evaporation and ion beam assisted deposition (IBAD) methods were utilized to fabricate depleted UO2 films and UO2 films with embedded Xe atoms, respectively. The films were fabricated at elevated temperature of 700°C and also subsequently annealed at 1000°C to induce grain growth and Xe atom redistribution. The goal of this work was to synthesize reference UO2 samples with controlled microstructures and Xe-filled bubble morphologies, without the effects attendant to rector irradiation-induced fission. Transmission electron microscopy (TEM) microstructural characterization revealed that fine Xe-filled bubbles nucleated in the as grown films and subsequent annealing resulted in noticeable bubble size increase. Reported results demonstrate the great potential IBAD techniques and UO2 films have for various areas of nuclear materials studies. [ABSTRACT FROM AUTHOR]

We have used a suite of diffraction, thermodynamic, and transport measurements to study the localized rattling of Al guest atoms in VAl10,1. The mean-square displacement of the rattling atom shows a concave-down temperature dependence. This is characteristic of an anharmonic vibration, the frequency of which increases with amplitude, akin to a particle in a box. We find that the rattling is best described in terms of a sixth-order interatomic potential, with negligible contributions from harmonic and quartic terms. The rattler has a characteristic temperature of θRM = 21 K and couples strongly to both the acoustic phonons and conduction electrons. The coupling to the phonons is evident from the large value of the Gruneisen parameter, which increases with decreasing temperature to &Ggr; = 43 at 5 K. Below 6 K, the electrical resistivity varies as T3, which can be explained in terms of electron scattering from damped sixth-order vibrations. VAl10,1 is a superconductor below Tc = 1.53 K, with an upper critical field of ∼ 1 kG. [ABSTRACT FROM AUTHOR]

We have measured the composition and temperature dependence of the shear moduli C' and C(44) for two-phase (alpha+beta)- and single-phase beta-PdH(x). In the two-phase region, the alpha- and beta-phases are coherent. Here, the composition dependence of C(44) and C' deviate negatively from a Vegard-type volume average. We attribute the deviations to two effects: (1) the partly in-series arrangement of the precipitate and matrix phases, relative to the externally applied stress, and (2) thermally activated anelastic relaxations involving the rapid motion of H interstitial atoms, leading to slight changes in the shape of coherent precipitates. The first effect is present for both C' and C(44) and is temperature-independent, whereas the second is present only for C' and is strongly temperature-dependent.