The plant communities and individual plant species in and around a salt playa near Goshen, Utah County, Utah were studied in relation to three environmental gradients. Forty-eight stands were sampled by means of meter square gradients. Frequency data for all participating plant species were taken. Soil samples were collected from each site and analyzed to establish the environmental gradients (i.e., total soluble salts, soil moisture and hydrogen ion concentration. Results indicate that community vegetation types respond differentially to the three gradients and can be segregated on the basis of one or more of the gradients. The total soluble salts gradient was found to be the most influential of the three gradients. Correlation analysis indicates that 45% of the diversity measured within the plant communities can be accounted for by the three gradients. Individual plant species distribution patterns are strongly influenced by the three gradients. Niche width measurements exhibited no correlation with the measured gradients.

This study focuses on techniques that can be used to fuel next generation reactors. The first two studies are new techniques for recycling used nuclear fuel (UNF) and the third is a method of separating uranium (U) from lithium fluoride (LiF) and thorium fluoride (ThF4) salt also known as FLiTh for a thorium (Th) fuel cycle. The first technique proposed for UNF recycling was to use the cladding as an anode to oxidize the zircaloy and dissolve it into a LiF, sodium fluoride (NaF), zirconium fluoride (ZrF4) salt. Zirconium (Zr) was also reduced and deposited on a tungsten (W) cathode at the same time transporting the Zr through the salt. As commercial zircaloy would be contaminated with UNF oxides, and the oxides will not oxidize as part of the electrochemical process, they would be left at the anode as the Zr is dissolved away. This means the deposited Zr, on the cathode, can be disposed of as low-level waste (LLW) or recycled back into the nuclear industry instead of being stored as high-level waste (HLW). The next technique was fluorination of UNF oxides using ZrF4. Using the same LiF-NaF-ZrF4 salt, uranium oxide (UO2), lanthanum oxide (La2O3), and yttrium oxide (Y2O3) were fluorinated into uranium fluoride (UF4), lanthanum fluoride (LaF3), and yttrium fluoride (YF3). By sampling and recording the change in concentration over time, the reaction rate of all three oxides was determined and a temperature dependent reaction rate was reported from 500°C to 650°C. A zirconium oxide (ZrO2) product layer developed on UO2, but it only slowed down the fluorination process but did not stop it. UO2 and Y2O3 fluorinated entirely but La2O3 did not. The solubility limit of LaF3 in the salt was determined to be the reason the reaction did not go to completion. The last technique was the electrochemical separation of U from FLiTh, to simulate irradiated Th that decays to protactinium (Pa). A constant, albeit small current, was used to deposit U on a W electrode without Th depositing with it. A liquid metal bismuth (Bi) electrode was used as well, and a constant current resulted in Th depositing with the U. To get just U to deposit, the current needed to be applied for a time and then no current applied for a time so the system could reach equilibrium. By cycling these two steps it was possible to get U to deposit in Bi without Th. / Doctor of Philosophy / This study focused on techniques useful to the fabrication of next generation reactor fuels. The first focus was on new techniques for recycling used nuclear fuel (UNF). Nuclear waste currently needs to be stored for hundreds of thousands of years to reach background radiotoxicity levels. If plutonium (Pu) is removed from the waste this time is limited to ten thousand years and if the other transuranics (TRU) are removed the waste only needs to be stored for 300 years to reach background radiotoxicity levels. As recycling UNF can make such a drastic difference, developing techniques for this are of utmost importance. The first technique studied was to show that the zirconium (Zr) in zircaloy cladding could be oxidized and transported through salt. This was done by applying a current between a zircaloy anode and tungsten (W) cathode, dissolving the cladding into the salt. The salt used was lithium fluoride (LiF), sodium fluoride (NaF), and zirconium fluoride (ZrF4) salt called FLiNaZr. This transported Zr through the salt and then deposited it on W. If this process was done with zircaloy contaminated with used nuclear fuel (UNF) oxides, the oxides would not dissolve into the salt as part of the process and would be left behind at the anode as Zr is transported through the salt, effectively separating the two. This alone leads to a 25% reduction in the weight of the UNF that needs to be stored. The next technique studied was converting the UNF oxides into fluorides. This was done by having it react with ZrF4 to make zirconium oxide (ZrO2) and UNF fluorides. The oxides studied here were uranium oxide (UO2), yttrium oxide (Y2O3), and lanthanum oxide (La2O3). UO2 and Y2O3 reacted until no material was left but La2O3 did not. This was due to lanthanum fluoride (LaF3) having a solubility limit in the salt that made it impossible for more to be made and stopping the reacting. The reaction rate for each oxide was found and the order of the reaction rates was Y2O3>UO2>La2O3. This process was a success and should be studied more to ensure it will work with all oxides found in UNF. The last technique studied was electrochemically separating uranium (U) from lithium fluoride and thorium fluoride (ThF4) salt. Thorium (Th) is another nuclear material, and while it cannot fission in a reactor it can be turned into an isotope of U, U-233, that can. To do this Th must be irradiated so it turns into protactinium (Pa) which can then be separated from the salt. In this study U was a surrogate for Pa as it is too radioactive to handle in this lab. First, an inert W electrode was used to deposit U metal, and once it was successful a liquid metal bismuth (Bi) electrode was used. A small constant current was able to deposit U on W without co-deposition of Th. For a Bi electrode, an alternating time of applying current and then letting the system rest was needed to deposit U without co-deposition of Th.

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Molten chloride salts have been proposed to be used as the primary coolant in molten salt reactors, and as the heat transfer fluid in concentrated solar power plants in next generation energy system design. The corrosive properties of molten chloride salts make it challenging to find appropriate structural materials for plant/system realization. In this work, two corrosion mitigation strategies are investigated to determine the relative corrosion performance of high temperature alloys in molten chloride salt mixtures: (1) chemical purification of salt mixture using a Mg sacrificial anode and (2) developing a protective oxide layer on the surface of high temperature alloys after pre-oxidation. These corrosion inhibitors are studied in combination with each other to determine the relative corrosion performance of three high temperature alloys: Incoloy 800H (chromia former), Haynes 214 (alumina former), and Noram SX (silica former). The unprotected and pre-oxidized alloys were exposed to molten chloride salt (62.5 wt % KCl + 37.5 wt % MgCl2·6H2O) with and without 1.7 wt % Mg as a corrosion inhibitor for 100 h at 700 °C under inert Ar atmosphere. SEM-EDS characterization was used to compare cross-sections and surfaces of each alloy exposed to molten salt with and without Mg additions. SEM-EDS cross-sectional characterization revealed significant Cr depletion in each unprotected alloy, and reduced Cr depletion in alloys immersed in molten chloride salt mixtures with chemical purification included. The addition of Mg metal to the salt mixture resulted in the precipitation of MgO on the alloy surfaces. The oxide deposition of MgO on components may impact the thermal and mechanical performance of the system. Therefore, the addition of Mg should be optimized for use in an operational system. Cross-sectional analysis identified the dissolution of Cr2O3 and SiO2 oxide scales and a stable Al2O3 oxide scale post-exposure. / Thesis / Master of Applied Science (MASc)

Different taste preferences and genetic variations may lead to particular food patterns that contribute to nutrient-related health outcomes such as hypertension. The objective of this study was to investigate single polymorphism of taste genes and salt taste perception in order to determine whether single nucleotide polymorphisms (SNPs) in the salt taste receptor genes (SCNN1B, TRPV1) affect salt taste perception in hypertensive participants. A cross-sectional study of 253 adults age 20-82 from each group, hypertensive (49%) and normotensive (51%), were enrolled. Salt taste recognition threshold, food preference score, and salt taste receptor genotype were determined. The hypertensive group had a higher salt taste recognition threshold than the normotensive group. However, there was no correlation between salt taste recognition threshold and salty food preference. Results also provide evidence that the polymorphism TRPV1, rs4790522 with AA genotype is associated with a lower sensitivity threshold of salt taste.

The studies of enzymes from extreme sources have gained significance due to their increasing potential applications. The proteins from halophiles (salt loving) have adapted to challenging environmental conditions and require salt for their structure and function. How halophilic proteins adapt to a hypersaline environment is still an intriguing question. It is important to mimic the environmental conditions of the sample under investigation with experimental techniques. In this study, structure and dynamic features of a halophilic enzyme have been investigated under high salt conditions. The acquisition of NMR data on high salt samples has always been problematic. We have devised a simple and elegant approach for obtaining NMR data for a protein in a high salt buffer that allows for virtually complete 1H, 13C, and 15N assignments. These data were then used to calculate the NMR derived structure of Haloferax volcanii dihydrofolate reductase in 3.5 M NaCl. Structure calculations showed that this protein folds in a similar manner as investigated in the crystal structures of Haloferax volcanii dihydrofolate reductase and Escherichia coli dihydrofolate reductase. To understand the effect of salt on flexibility as well as activity, NMR relaxation studies at 3.5 M and 1.0 M salt concentration were carried out. NMR dynamics of this enzyme revealed that the loss of activity as the salt concentration is lowered is due to lose in the inherent flexibility across the backbone, particularly in the catalytic loops.

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Nanoparticles have been found to have an increasingly wide range of applications including drug delivery systems, chemical sensors, biomolecule sensors, single electron devices, catalysis, Li-ionbatteries, andsolarcells. Avarietyofmethodshavebeenused to produce nanoparticles, but one widely used approach is the application of reverse micellenanoreactorswherebyblockco-polymersareusedtoencapsulateprecursorsalts and serve as a vessel for precursor salts to react. As the encapsulation of precursor salts can be a multi-step process, some nanoparticle formulations have proven difficult to make within the reverse micelle nanoreactor. To fully understand the difficulties in nanoparticle formation, we need to have a method to probe the internal structure of the reverse micelle. This thesis presents a novel method for probing the internal structure of the reverse micelle using a quantitative mechanical mapping (QNM) mode for atomic force microscopy (AFM). Unloaded reverse micelle nanoreactors were analyzed using the QNM AFM mode. A decrease of the Young’s modulus was noted through the centroid of the reverse micelle. Many models were applied to describe the noted decrease of Young’s modulus. The end result indicated that intrinsic differences between the mechanical properties of polystyrene and poly(2vinyl pyridine) and the co-polymer orientation lead to the measured decrease in Young’s modulus through the centroid. Results from the unloaded case were used to explain changes to the reverse micelle nanoreactor after loading with precursor salts. Across all precursor salts similar trends were noted, however there was no consistent relative Young’s modulus or molar salt loading ratio noted within the trends. Three distinct loading zones were consistent acrosstheprecursorsalts. Region I wastypifiedbyaslightdecreaseinrelativeYoung’s modulus with small resultant nanoparticles. Region II was typified by linear increases in relative Young’s modulus for increases in the molar salt loading ratio. Region III was found to have two possible outcomes, either the micelle reach a maximum effective infiltration, where the relative Young’s modulus ratio no longer increases for increased molar salt loading ratio, or the micelle would unravel for increased molar salt loading ratio. Further studies should be done to confirm the existence of the universal loading regions across further co-polymers, solvents, and precursor salts. / Thesis / Master of Applied Science (MASc)