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Executive SummaryUltrasonic nondestructive evaluation (NDE) and inspection of cast austenitic stainless steel (CASS) components used in the nuclear power industry is neither as effective nor reliable as is needed. With current ultrasonic methods these limitations are in large part due to the detrimental effects of wavemicrostructure interactions on the interrogating ultrasonic beam and interference that results from ultrasonic backscatter. The root cause of these phenomena is the coarse-grain microstructure inherent to this class of materials. Some ultrasonic techniques are found to perform better for particular microstructural classifications and this has led to the hypothesis that an ultrasonic inspection can potentially be optimized for a particular microstructural class. For optimized ultrasonic technique selection, methods will be needed to reliably classify the microstructure in-situ, which is then used to guide the selection and optimization of the inspection. This document summarizes scoping experiments that investigate potential in-situ ultrasonic methods for classification and/or characterization of the material microstructures in CASS components, when making measurements from the outside surface of a pipe.The focus of this preliminary study was to evaluate ultrasonic measurement methods to determine if responses from different known microstructures can be differentiated and hence if in-service characterization of cast austenitic stainless steel (CASS) is potentially feasible. On the basis of an initial literature evaluation, two ultrasonic parameters, (i) the time-of-flight ratio between shear and longitudinal waves and (ii) the attenuation for normal incidence longitudinal waves, were selected for investigation. Scoping experiments were performed to determine the ability of these measured parameters to discriminate between different microstructures in CASS components. The objective was to determine if a more thorough and staged exploration would be justified in progressing toward the real-time characterization of CASS for use as feedback to optimize current or new ultrasonic in-service inspection methodologies. With this objective in mind, measurements were restricted to techniques that potentially should be robust if carried forward to an eventual field implementation.The first parameter investigated was a time-of-flight ratio of a normal incidence shear wave to that of a normal incidence longitudinal wave (TOFRSL). The ratio removes dependency on component thickness which may not be accurately known or reported in the field. The second parameter was the attenuation of a normal incidence longitudinal wave. The selected CASS specimens used for the experimental study were five equiaxed-grain material samples and five columnar-grain material samples, and these were used for a two-class discrimination problem.TOFRSL estimates and a threshold algorithm classified all 10 material samples correctly and indicated a potentially reliable and robust technique. Qualitative longitudinal wave attenuation estimate...

SummarySnohomish Public Utility District #1 (SnoPUD) proposes to deploy two OpenHydro tidal turbines in Admiralty Inlet, Puget Sound. The fisheries service of the National Oceanic and Atmospheric Administration (NOAA Fisheries) has expressed concerns that the turbines may cause a risk for the highly endangered Southern Resident Killer Whale (SRKW) population if a whale is struck by an operating turbine. NOAA Fisheries is responsible for protecting the (fewer than 90) SRKWs under the Endangered Species Act and the Marine Mammal Protection Act. Because the SRKW numbers are so small, significant injury of a single animal could place the population in jeopardy.The potential risk to a SRKW can be parsed into the probability that a whale would encounter a turbine, the probability that the encounter would injure the whale, and the severity of any injury. During a meeting with representatives of SnoPUD, OpenHydro, the Department of Energy, and NOAA Fisheries, participants agreed that the probability of a SRKW encountering a turbine by chance is negligibly small as the whales spent greater than 97 percent of their time in Admiralty Inlet in the top 30 meters of water, while the turbines are located at 55 meters of depth, and the SRKW have highly evolved acoustic sensory capabilities that would help them detect the presence of a turbine. NOAA Fisheries expressed concerns over the potential severity of a strike on a SRKW should it occur. A proposed solution was to conduct an estimate of the level of injury that might occur from an encounter between a turbine blade and a SRKW, which would allow NOAA Fisheries to determine the permitting requirements for the tidal project.Pacific Northwest National Laboratory (PNNL) and Sandia National Laboratories (SNL) were tasked by the Department of Energy to carry out an analysis of the mechanics and biological consequences of strike of a SRKW by an OpenHydro turbine blade. The approach taken by the two laboratories was to: 1) develop a scenario for the most severe strike of a SRKW; 2) determine the morphological and biomechanical properties of SRKW tissues that might be affected by a strike; 3) model the forces of a strike; and 4) estimate the potential effects on SRKW tissue and bone of a strike.PNNL and SNL developed a worst case exposure scenario for strike of a SRKW. SNL modeled a turbine blade (based on proprietary design data obtained from OpenHydro), and calculated the force of blade impact on the head of an adult male SRKW, weighing approximately 4000 kilograms. The adult SRKW was selected for the model because an adult has a large body mass where more of the energy in a blade strike will be absorbed by the whale's tissue rather than going into momentum transfer that would push the whale out of the path of the turbine blade. This scenario would maximize the risk of injury to the SRKW. Although a juvenile SRKW might intuitively be considered to be at greater risk of injury, because of much smaller mass (~500 kg) more of the energy in the blade strike would go into momentum trans...

We present a combined first-principles and experimental study of the electrical resistivity in aluminum and copper samples under pressures up to 2 GPa. The calculations are based on first-principles density functional perturbation theory, whereas the experimental setup uses a solid media piston-cylinder apparatus at room temperature. We find that upon pressurizing each metal, the phonon spectra are blue-shifted and the net electron-phonon interaction is suppressed relative to the unstrained crystal. This reduction in electron-phonon scattering results in a decrease in the electrical resistivity under pressure, which is more pronounced for aluminum than for copper. We show that density functional perturbation theory can be used to accurately predict the pressure response of the electrical resistivity in these metals. This work demonstrates how the phonon spectra in metals can be engineered through pressure to achieve more attractive electrical properties.density functional theory | electron-phonon coupling | high-pressure conductivity S train has proven to be an effective means of modifying the electronic structure in semiconducting materials, particularly band gap modulation in metal-oxide-semiconductor field-effect transistors (1-6). Strain also affects the phonon structure and transport properties of metals, which have no band gap to modulate, and may be used to engineer more attractive electrical properties at both the macroscale and the nanoscale.The nonzero electrical resistivity of a metal has two main contributions: the presence of defects and the vibrations of the lattice atoms about their equilibrium sites (7). Scattering events between electrons and vibrational quanta (phonons) give rise to the finite electrical resistivity in pure samples. First-principles calculations have proven to be remarkably successful in giving accurate descriptions of the phonon-induced electrical resistivity in metals (8-10). It also has been shown that the phonon-mediated properties, including the electrical resistivity and the superconducting transition temperature, can be altered under pressure (11-13). It has been suggested that the electrical transport properties due to the electron-phonon interaction in aluminum show a particularly strong response to interatomic spacing, particularly when the system is subject to extreme quantum confinement (14,15).Studies of the effect of pressure on the superconducting properties of aluminum suggest that superconductivity is suppressed through a reduction in the critical temperature, T c , as the pressure is increased (11,12,(16)(17)(18). It also has been reported that the electron-phonon coupling constant, λ, decreases in aluminum under pressure (11,16), but a quantitative extension to the electrical resistivity under pressure is lacking. Cheung and Ashcroft (13) suggested a decrease in the electrical resistivity of aluminum under volume compression by using a primitive pseudopotential model with experimentally determined interatomic force constants, but the pressures corresponding t...