An ultra-high burnup metallic inert matrix nuclear fuel concept is being characterized and evaluated by Lawrence Livermore National Laboratory based on a metal matrix fuel concept originally developed at the Bochvar Institute in Russia. The concept comprises a dispersion of uranium metal microspheres in a Zr-based alloy matrix that provides thermal bonding between the fuel particles and the cladding material. The objective of this study was to experimentally evaluate both the microstructural and thermophysical properties of Zr-Fe-Cu alloys. The experiments and analyses described were divided into three main parts, nominally based on the analysis methods used to examine the alloys. An Electron Probe Microanalyzer (EPMA) was used to characterize the metallurgical properties of the proposed matrix alloys. The groups of alloys were cast using a high temperature inert atmosphere furnace. The cast alloys showed the expected combination of phases with the exception of the ZrFe2 Laves phase which was predicted for the Zr-12Fe-15Cu1 alloy but was not detected. The Zr-12Fe-5Cu alloy consisted of a Zr solution phase dispersed in a matrix of two different intermetallic phases. The second alloy, Zr-12Fe-10Cu, did not produce a homogenous mixture and consisted of two distinct phase morphologies. The top half of the sample was Zr rich and contained Zr precipitates dispersed in a matrix of intermetallic compounds while the bottom half consisted solely of intermetallic compounds. The third alloy, Zr-12Fe-15Cu, was comprised of four different intermetallic phases three of which had the same apparent Zr_(2)(Fe,Cu) structure but had distinct phase morphologies based on the Backscatter Electron (BSE) images. Upon determining the phase morphologies of each of the fabricated alloys Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were used to measure phase transformation and melting temperatures. Little difference was observed between the as-cast and annealed samples. The transitions shifted slightly to higher temperatures and the annealed Zr-12Fe-15Cu alloy only had two transitions compared to three seen in the as-cast samples. Slight changes were observed in the melting temperatures between the as-cast and annealed alloys. Zr-12Fe-5Cu had the largest melting temperature (886.3°C) while Zr-12Fe-10Cu had the smallest melting temperature (870°C). The third alloy, Zr-12Fe-15Cu, had a melting point just below that of Zr-12Fe-5Cu at 882.7°C. Light Flash Analysis (LFA) was implemented to determine the low temperature (20-260°C) thermal diffusivity values of each alloy. The as-cast measurements were more precise than the annealed samples, most likely the result of non-ideal sample integrity prior to loading. Each of the three alloys showed a linear increase in thermal diffusivity over the temperature range. Values for Zr-12Fe-5Cu ranged from 3.54 ± 0.06 mm2/s to 4.42 ± 0.10 mm^(2)/s. The Zr-12Fe-10Cu alloy had maximum and minimum values of 4.19 ± 0.22 mm^(2)/s and 3.17 ± 0.16 mm^(2)/s, respectively. Lastly, Zr-12Fe-15Cu had the largest thermal diffusivity ranging from 3.52 ± 0.15 mm^(2)/s at 20°C to 4.64 ± 0.16 mm_(2)/s at 260°C. Overall, the data from the LFA measurements showed that the Zr-Fe-Cu alloy system had similar diffusivity values compared to other common reactor materials.

The ultimate goal of this project was to improve the sensitivity and detection limits of inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) and then apply it to the speciation analysis of As. To this end, two approaches were taken: the use of organic modifiers and that of a pre-evaporation interface between the spray chamber and the plasma torch. The radial profiles of some background ions and analytes in three different matrices (1% HNO3, 1% HNO3 with 2% v/v methanol, 1% HNO3 with 0.2% m/v sodium dodecylsulfate (SDS)) were investigated in ICP-TOFMS. Although these concentrations of methanol and SDS induced the same increase (37%) in sample introduction efficiency, the change in analyte signal as a function of m/z followed opposite trends in these two matrices. The results show that matrix effects arising from different organic modifiers affected the distribution of ions in the plasma differently as a result of changes induced in the predominant ionisation mechanisms in the plasma. The effect of a pre-evaporation interface on the distribution of ions in ICP-TOFMS was also investigated by spatial profiling, which showed that the optimal axial position of all elements shifted closer to the load coil. Furthermore, the radial profiles became significantly narrower and Gaussian. The decrease of droplet size thus improved the sensitivity and detection limits for multi-elemental analysis. A further investigation of the effect of the pre-evaporation interface revealed that, for cationic analytes, the signal enhancement had an inverse dependency on analyte mass upon heating the interface. In the case of As, a signal enhancement upon heating the interface only resulted when concomitant ionic analytes were present or with a 0.01 M NaOH matrix. All these observations could be rationalised by changes in the number of Coulomb fission events occurring during pre-evaporation, which depend on the size and charge of droplets, as well as the identity and concentration of the matrix. Finally, the baseline separation of four As species by ion exchange liquid chromatography with detection by ICP-TOFMS and application of the pre-evaporation interface tube to As speciation were achieved using a mobile phase of NH4NO3, following an investigation of its matrix effects. / Thesis (Ph.D, Chemistry) -- Queen's University, 2007-07-12 13:51:55.115

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Avian point counts were conducted in tall-grass prairie fragments and adjacent grassland and agricultural matrix habitat in southern Manitoba. Bird density/abundance was compared between habitat types, while variables within prairie at local, patch or landscape level were modeled to determin avian habitat selection. Prairies and matrix grassland habitat supported the same number of species in both years, and densities of all focal bird species were the same in non-native grasslands as compared with native tall-grass prairies. Overall species richness in tall-grass prairies was mainly driven by vegetation variables. Variable responses to habitat structure and composition between avian species indicate that managing grasslands to promote heterogeneity is important to sustain a diverse assemblage of avian species. As individual species were affected most strongly by vegetation structure and richness, it follows that management of prairie vegetation through techniques such as grazing and prescribed burning could optimize habitat usability for birds.

This thesis is devoted to investigation of some properties of the permanent function over the set Omega_n of n-by-n doubly stochastic matrices. It contains some basic properties as well as some partial progress on Foregger's conjecture. CONJECTURE[Foregger] For every n\in N, there exists k=k(n)>1 such that, for every matrix A\in Omega_n, per(A^k)<=per(A). In this thesis the author proves the following result. THEOREM For every c>0, n\in N, for all sufficiently large k=k(n,c), for all A\in\Omega_n which minimum nonzero entry exceeds c, per(A^k)<=per(A). This theorem implies that for every A\in\Omega_n, there exists k=k(n,A)>1 such that per(A^k)<=per(A).

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