[en] A field site where a minor spill of hydrocarbon material had occurred was chosen to study the effects that augering would have on soil decontamination. The soil was impermeable moist, clay. Therefore, remediation methods that rely on porous soil would not have been appropriate in this case. Excavation was not considered feasible either, since studies have shown that during excavation more than 90% of the volatile components are released to the atmosphere, causing safety hazards. Efficient bioremediation needs the presence of nutrients and oxygen. Before the site was augered, nitrogen and phosphorous fertilizers were spread over the area. Augering allowed the percolation of nutrients to 90 cm depth, and increased the redox potential. It held the volatilization of hydrocarbons to less than 2% of the initial concentration. Total hydrocarbon contaminants were reduced by 78% in 116 days. It was concluded that augering was economical and that it protected the environment by minimizing the release of volatile compounds while enhancing soil remediation. 8 refs., 7 tabs., 7 figs

[en] This project is investigating the chemical processes that govern actinide sequestration in grout materials with the goal of determining the long-term behavior of grouts used to stabilize actinides in source-terms such as high level waste tank heals. Two grouts contained portland cement, blast furnace slag and fly ash, with one formulation containing zeolite and the other fluorapatite. Earlier experimental work was conducted with funds from DOE/West Valley. CEMS funding allowed further exploration of grout behavior, beyond the scope of the original work which consisted of both batch and flow-through column experiments. The primary focus was the late stage behavior of actinides in the grout system when it is expected to be open to the atmosphere and groundwater, resulting in decreases of pH and interactions of U (and other elements) with dissolved carbonate

[en] A fast imaging electron detector is being developed as part of the Toroidal Energy- and Angle-Resolved Electron Spectrometer (TEARES), a high-resolution electron spectrometer for use on synchrotron sources. The analysed solid angle of TEARES is about 100 times greater than that of a conventional hemispherical analyser of similar radius and entrance slit sizes. A 'typical' solid sample at a third-generation synchrotron source would yield count rates in excess of 1 GHz, >10³ times the capability of available imaging electron detectors. We describe a prototype detector based on low-resistance microchannel plates and an adaptation of the cartesian two-dimensional CODACON encoder that aims to achieve a relatively modest 2 MHz counting rate with 32 by 128 simultaneous energy and angle channels. The encoder pattern has been optimised for the output electron distribution of TEARES and directly generates a binary address for each event using simple electronics and the minimum number of signal channels

[en] IPF has recently investigated isotope production with proton beams at energies other than the 100-MeV currently available to the IPF beam line. To maximize the yield of a particular isotope, it is necessary to measure the production rate and cross section versus proton beam energy. Studies were conducted at 800 MeV and 197 MeV to determine the cross section of Tb-159. Also, the ability to irradiate targets at different proton beam energies opens up the possibility of producing other radioisotopes. A proof-of-principle test was conducted to develop a 40-MeV tune in the 100-MeV beam line. Another parameter explored was the beam current, which was raised from the normal limit of 250 μA up to 356 μA via both power and repetition rate increase. This proof-of-principle test demonstrated the capability of the IPF beam line for high current operation with potential for higher isotope yields. For the full production mode, system upgrades will need to be in place to operate at high current and high duty factor. These activities are expected to provide the data needed for the development of a new and unique isotope production capability complementing the existing 100-MeV IPF facility.

[en] The abundance ratio of ¹3^C to ¹2^C was proposed as a measure of the effectiveness of remediation of hydrocarbon contamination, based on the mass differences between the two isotopes and the known preference of biological processes for the lighter isotope. In addition to monitoring changes in total hydrocarbon it should also be possible to track individual components using this technique. Tracking individual hydrocarbons could confirm degradation of individual components of C5+ mixtures in the field. 13 refs., 2 figs. i

[en] We report measurements of the superfluid fraction of 4He confined in small channels 9.4 nm high, 19 μm wide by 2000 μm long. This confinement corresponds to a film of finite lateral extent. The data show a shift in the transition to a lower temperature which is larger than the logarithmic dependence expected from finite-size scaling and Berezinski -Kosterlitz-Thouless theory. This shift however is smaller than the one proposed by Sobnack and Kusmartsev for this kind of geometry. When examining the behavior of the shift for confinement at several widths, we found that the shift favors a power law with a larger exponent than predicted by Sobnack and Kusmartsev

[en] The Spallation Neutron Source (SNS) is one of the largest science projects in the United States, with total cost near 1.4 Billion Dollars. The limiting factor of the facility had always been assumed to be the lifetime of the target window due to radiation damage. After further investigation, the lifetime of the target was determined not to be limited by radiation damage but by cavitation damage. The cavitation damage derives from pressure waves caused by the beam energy deposition. Vapor bubbles form when low to negative pressures occur in the mercury near the stainless steel target window due to wave interaction with the structure. Collapse of these bubbles can focus wave energy in small liquid jets that erode the window surface. Compressibility of the mercury can be enhanced to reduce the amplitude of the pressure wave caused by the beam energy deposition. To enhance compressibility, small (10 to 30 micron diameter) gas bubbles could be injected into the bulk of the mercury. Solubility and diffusivity parameters of inert gas in mercury are required for a complete mechanical simulation and engineering of these strategies. Using current theoretical models, one obtains a theoretical Henry coefficient of helium in mercury on the order of 3.9E15 Pa-molHg/molHe at 300 K. This low solubility was confirmed by a direct, offline experimental method. Mercury was charged with helium and any pressure change was recorded. Any pressure change was attributed to gas going into solution. Therefore, with the sensitivity of the experiment, a lower limit of 9E12 Pa-molHg/molHe was placed on the mercury-helium system. These values guarantee a stable bubble lifetime needed within the SNS mercury target to mitigate cavitation issues.

[en] Magnesium has multiple dislocation and twinning systems with starkly different properties, which make its plastic deformation strongly anisotropic and highly complex. Existing empirical interatomic potentials fail to capture the full scope of these properties, making current molecular statics and dynamics simulation results of limited quantitative and predictive use. Here, based on the work by Kim et al, a new modified embedded-atom method potential for magnesium is introduced and rigorously validated against existing ab initio, continuum theory and experimental results. The new potential satisfactorily reproduces all the necessary mechanical properties for plastic deformation, including the various generalized stacking fault energy surfaces, dislocations core structures, Peierls stresses, surface energies and basal plane cohesive strength. The capability of this potential to accurately describe all the important slip systems and fracture behavior makes it valuable for future realistic atomistic studies of general magnesium deformation and failure problems. (paper)

[en] Recently, it was shown that two confined regions of liquid ⁴He exhibit a proximity effect over distances much larger than the correlation length ξ[1; 2]. Here we report measurements of the superfluid fraction ρ_s/ρ and specific heat c_p of a 33.6 nm film. Comparison with previous data from a 31.7 nm film in contact with an array of 34 × 10⁶ (2 μm)³ boxes of ⁴He allows us to show quantitatively the enhancement in ρ_s/ρ and c_p due to the presence of the boxes in the temperature region where the film orders. The enhancement in ρ_s/ρ is observed up to distances 650 times the bulk correlation length. This anomalously large length scale is analogous to a giant proximity effect observed in High-T_c superconductors (HTSC)[3].

[en] Switchgrass (Panicum virgatum) has been identified as a model dedicated energy crop species. After a perennial grass is established, the major variable costs are for nitrogen (N) fertilizer and harvest. Prior to establishing switchgrass on millions of ha in a particular agro-climatic region, it would be useful to determine switchgrass yield response to N and its response to harvest frequency relative to alternative grass species. The objective of this research is to determine biomass yield response to N for four perennial grass species and to determine the species, N level, and harvest frequency that will maximize expected net returns, given the climate and soils of the U.S.A. Southern Plains. Yield data were produced in an experiment that includes four species (switchgrass, bermudagrass (Cynodon dactylon), weeping lovegrass (Eragrostis curvula), and carostan flaccidgrass (Pennisetum flaccidum)), four N levels, and two harvest levels. Linear response plateau (LRP), linear response stochastic plateau (LRSP), and quadratic response (QR) functions are estimated. For all combinations of biomass and N prices considered, the optimal species is switchgrass. For most price situations, it is economically optimal to fertilize established stands of switchgrass with 69 kg N ha^-1 yr^-1 and to harvest once yr^-1 after senescence. (author)