When soluble boron is used to control reactivity, there are two particular events which can challenge long-term core cooling (LTCC) during the small break loss-of-coolant accident (SBLOCA): boron precipitation and boron dilution. The initial consequences of the SBLOCA are mitigated by the emergency safety systems, but the core continues to boil. As boron is less volatile than steam, the steam is virtually boron free. All the boron remains in the core, the boron concentration in the core rises. If the solubility limit is reached, precipitation could occur. The boron precipitation event was historically considered to be bounded by the large break accident. However, there are characteristics of the SBLOCA which cannot be neglected and an SBLOCA specific methodology is required. On the opposite end of the boron concentration spectrum is the SBLOCA boron dilution event. The steam generators remove heat from the primary and condense the steam. The condensation of the boron-free steam can result in the accumulation of a deborated slug of water. If natural circulation restarts, the slug can be transported toward the core and potentially reduce the core boron concentration enough to induce a recriticality. This thesis describes two analytical methodologies for these SBLOCA LTCC events. The two methodologies have a similar approach. Both use transient system analyses for inputs to and justification of the follow-on boron concentration calculations. For boron precipitation, a maximized concentration is calculated with the Small Break Boron Precipitation model. For boron dilution, a minimized core inlet concentration is calculated using computational fluid dynamics. / Master of Science

Field experiments were conducted during the 1985 growing season on six soils in the Atlantic Coastal Plain region and one from the Piedmont region to determine the response of irrigated corn (<i>Zea mays</i> L.) to boron application. Two treatments applied to each of the soils consisted of 1) a control and 2) both band and foliar boron applied at rates of 2.0 and 0.5 kg ha⁻¹, respectively, as Solubor when corn plants were in the V5 to V6 growth stage. Corn grain yields averaged 13,485 kg ha⁻¹ across treatments on the seven soils. Based on published calibration data for the hot water soluble boron procedure, a corn grain yield response to boron application was not expected on any of the seven soils. Nevertheless, boron application increased corn grain yield from 13,485 kg ha⁻¹ on the control treatment to 14,300 kg ha⁻¹ on the plus boron treatment for one of the seven soils, an Altivista loamy sand. This soil had a hot water soluble boron concentration of 0.56 mg kg⁻¹ and a Mehlich 3 extractable boron concentration of 0.78 mg kg⁻¹. The six soils for which boron application did not increase yields had hot water soluble boron concentrations from 0.55 to 0.92 mg kg⁻¹ and Mehlich 3 extractable boron concentrations from 1.02 to 1.33 mg kg⁻¹. The boron concentration in whole corn plants sampled at the V5 to V6 growth stage was 6.7 mg kg⁻¹ on the Altivista soil where boron application increased corn grain yields and ranged from 9.6 to 103.1 mg kg⁻¹ on the six soils where boron application did not increase yields. The boron concentrations in ear leaves sampled at the early silk growth stage ranged from 8.5 to 18.6 mg kg⁻¹ and in corn grain from 0.66 to 3.31 mg kg⁻¹ on the control treatments of the seven soils. Ear leaf and grain boron concentrations were 10.7 and 0.74 mg kg⁻¹ for plants grown on the control treatment on the Altivista loamy sand, respectively. It can be concluded that, of the plant tissue and soil test procedures evaluated, boron concentration in whole young plants and Mehlich 3 extractable B were the most promising for diagnosis of boron deficiency in corn plants. Nevertheless, research is required on more soils before boron concentrations in young plants and Mehlich 3 extractable B can be used as a routine procedure for detection of boron deficiency in corn plants. / M.S.

Greenhouse and laboratory experiments were conducted to investigate the distribution of native B, the availability of native and applied B in 14 Virginia soils and the specific reactions of B in soil and hydroxy Al and Fe systems. Total B in the 14 soils ranged from 21.5 to 96.3 mg kg⁻¹. Only a small portion of the total B was in soil solution, non-specifically and specifically adsorbed forms and Mn minerals. These fractions of B are readily available to plants. A large part of the total B was associated with non-crystalline and crystalline Al and Fe minerals and soil silicates. These forms of B contribute little to B absorption by plants. Hot water soluble B, NH₄-acetate extractable B, mannitol exchangeable B and Mehlich III extractable B from the soils closely correlated with the concentrations in corn plants from native B in the greenhouse experiment. A yield response of corn plants to B application did not occur on the soils. Both tissue B concentration from applied B and maximum B adsorption by the soils closely correlated with soil clay, hydroxylamine hydrochloride extractable Mn and NH₄—oxalate (pH 3.25) extractable Al and Fe (under UV light). These data indicated that soil clay and Al-, Fe- and Mn-oxides and hydroxides have high affinities to adsorb B in plant unavailable forms. Boron adsorption on both gibbsite and goethite was pH and temperature dependent. At pH 6.5, boric acid was major species in the system and B was absorbed by the negatively charged surface of gibbsite and the positively charged surface of goethite. At pH 10, borate was primarily species in the system and B was adsorbed on negatively charged surfaces of both minerals. Boron adsorption was greater at pH 10 than at pH 6.5. An increase in temperature increased B adsorption on both minerals at both pH levels. This indicated that the B adsorption was an exothermic process. Boron adsorption on gibbsite and goethite shifted the ZPC of the minerals downward. This verified that specific B adsorption occurred on the surfaces. Aluminum substitution in goethite increased the affinity of the surface for B adsorption. / Ph. D.

Made available in DSpace on 2014-06-11T19:22:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-09-06Bitstream added on 2014-06-13T18:07:57Z : No. of bitstreams: 1 biscaro_t_me_botfca.pdf: 707769 bytes, checksum: a5322c5ecf4e0883a2d95b9be40fdd31 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Em algumas condições não se têm obtido correlações entre os teores de B do solo, extraído com água quente, o teor de boro na planta e a produtividade da soja no Estado do Mato Grosso, mais precisamente na região de Campo Novo do Parecis. Sabe-se que o boro é um nutriente fortemente adsorvido nas partículas minerais do solo. Objetivou-se com este trabalho submeter amostras de solo de uma determinada área de estudo, na qual foi cultivada soja por três anos consecutivos e posteriormente cultivado algodão, a diferentes métodos de extração de boro, a fim de se estabelecer correlações entre a dose de boro na planta, a dose de nutriente aplicada e o teor de boro no solo disponível às plantas e, ainda, com a produtividade da soja. Amostras de solo, cultivadas com soja, coletadas por ocasião da condução do experimento no campo, foram analisadas quanto à concentração de B extraída pelos métodos: água quente modificado com solução de BaCl2 1,25 g L-1 (recomendado e chamado de método da água quente pelo IAC); água quente modificado com solução de CaCl2 0,01 mol L-1,a quente e água quente tradicional (o qual é preconizado por muitos autores como o método oficial) para dessa forma, tentar quantificar a real disponibilidade de boro neste solo, caracterizado como um LATOSSOLO VERMELHO AMARELO (LVA), possibilitando a determinação de um nível crítico. Ainda, durante o período de condução do trabalho, foi feito um estudo de adsorção de B nas amostras, e um estudo do comportamento da lixiviação do nutriente em colunas de solo, procurando verificar o efeito das adubações na dinâmica do nutriente. Em relação aos métodos de extração de boro no solo, o CaCl2 foi o que apresentou correlação positiva e significativa com o boro presente no tecido vegetal nos três anos agrícolas. Os métodos do BaCl2 e... / In some conditions, doesn't have obtained correlations among boron content in soil, boron extracted by hot water, boron content in plants and soybean productivity in a region (Campo Novo do Parecis) of the state of Mato Grosso/Brazil. This work was carried out to submit soil samples from determined area of study where was tillage soybean for three subsequent years and after tillage cotton, to differents extraction methods by boron with the aim to establish correlations among, amount of boron content in plants, amount of nutrient putted in soil, boron content in soil disponible to plants and the productivity. Soil samples obtained during the conduction of experiment on field were analyzed to predict the amount of boron in soil by the methods: hot water modified with BaCl2 solution (recommended and called by hot water from IAC - Instituto Agronômico de Campinas/SP-Brazil), hot water modified CaCl2 0,01 mol L-1 solution and hot water traditional (which is preconized by many authors like the official method) to this way try to quantify the real situation of boron disponibility in this soil, characterized like a Yellow Red Latossol, to take the determination of a critical level. During the conduction period of this work was made an adsorption study in the samples, and still a study of boron leaching behavior in soil columns, to verify fertilizer effect in nutrient dynamic. The extraction method with CaCl2 presented positive and significative correlation with boron present in soybean leaves on three subsequent farm work years. BaCl2 method and hot water traditional also presented positives and significatives correlations each one in two farm work years, this results were expected in function of similarity among three methods, it's an evidence that there is a method with capacity to predict boron disponibility in soils of Mato Grosso... (Complete abstract, click eletronic address below)

The incidences of suspected Boron (B) deficiency have increased recently in Kentucky tobacco fields, potentially due to recent changes in management practices. The symptoms observed in the field include; hollow stalk, stunted growth, deformed or no bud formation, small slits on the lower leaf midrib and uncontrollable breaking of the midrib approximately two inches from the stalk. B is a micronutrient tobacco needs in minute amounts, however excessive additions of B could cause toxicity. The objectives of this work were to 1) establish critical points for B sufficiency, 2) describe and define B deficiency and toxicity symptoms and 3) develop field strategies to aid in the mitigation of B deficiency. A general nutrient response curve was generated utilizing solution culture experiments. The peak of the response curve appeared to occur at solution B concentration of 100 µM. Trace-levels of B contamination and small plant size in the solution culture limited the development of deficiency symptoms. Toxicity was observed at solution concentrations of 400 µM and above. Despite choosing sites with a history of B deficiency, deficiency symptoms were not observed during this study. Toxicity was observed when 0.56 kg B/ha or greater was applied as simulated transplant water treatments. No toxicity was observed when B was applied as a soil broadcast or foliar application. Recommendations are to apply B with caution as a broadcast application to avoid potential problems with toxicity. Additional research is required to refine the nutrient response curve and better understand B deficiency.

The eastern margin of the Proterozoic Athabasca Basin in northern Saskatchewan is host to several of the highest-grade unconformity-related (U/C-related) uranium deposits in the world. Many researchers agree that uranium deposition occurred due to oxidized basinal brines transporting uranium mixing with reducing fluids or interacting with reduced rock causing uranium to precipitate, although the source of the uranium is still an unresolved and highly debated subject. Boron isotopic signatures, preserved in refractory minerals such as tourmaline, can aid in determining the source of fluids and P-T conditions during crystallization whereas lithium isotopic fractionation is indicative of weathering, hydrothermal alteration, and/or igneous and metamorphic processes. For this study a suite of fresh to strongly altered basement samples were selected from multiple sites below the eastern Athabasca Basin to measure the bulk delta7Li, delta11B and Pb-Pb isotopic signatures. Kinetic modelling of the Li and B isotopic systems suggest that both systems are slightly conservative of their original fluid reservoir, and by calculating the Damkohler numbers (ND) it is predicted that delta11B will be more indicative of the fluid source whereas lithium isotopes will equilibrate over shorter distance. However, both isotopic systems will fractionate with large concentration changes. Significant variations were observed for both delta7Li and delta11B, delta7Li values ranged from 0 to 14 ‰, the range in delta7Li was interpreted to be representative of both partial melting of metasediments to form granitic pegmatites and hydrothermal fluids. In comparison the range for delta11B was much larger from -16 to +17‰, within the dataset there appeared to be regional isotopic differences but unfortunately this dataset was too small to determine regional isotopic patterns. For each region the delta11B for the pegmatites was often heavier than the metasedimentary samples suggesting a metasedimentary source for the granitic pegmatites. Elevated U concentrations and decreasing 207Pb/206Pb ratios in both altered and unaltered samples suggest radiogenic Pb and U are present both in the basement and in fluids transporting U through the basement. Partial digestion 207Pb/206Pb ratios range from the common 207Pb/206Pb ratios of 0.7 to radiogenic 207Pb/206Pb ratios of 0.1. The radiogenic 207Pb/206Pb are indicative of either resetting of residual material during fluid migration or radiogenic fluids sources interacting with the rocks of this study.

Doctor of Philosophy / Department of Chemical Engineering / James H. Edgar / Semiconducting icosahedral boron arsenide, B[subscript]12As[subscript]2, is an excellent candidate for neutron detectors and radioisotope batteries, for which high quality single crystals are required. Thus, the present study was undertaken to grow B[subscript]12As[subscript]2 crystals by precipitation from metal solutions (nickel) saturated with elemental boron and arsenic in a sealed quartz ampoule. B[subscript]12As[subscript]2 crystals of 8-10 mm were produced when a homogeneous mixture of the three elements was held at 1150 °C for 48-72 hours and slowly cooled (3°C/hr). The crystals varied in color and transparency from black and opaque to clear and transparent. X-ray topography (XRT), Raman spectroscopy, and defect selective etching confirmed that the crystals had the expected rhombohedral structure and a low density of defects (5x10[superscript]7 cm[superscript]-2). The concentrations of residual impurities (nickel, carbon, etc) were found to be relatively high (10[superscript]19 cm[superscript]-3 for carbon) as measured by secondary ion mass spectrometry (SIMS) and elemental analysis by energy dispersive x-ray spectroscopy (EDS). The boron arsenide crystals were found to have favorable electrical properties (μ = 24.5 cm[superscript]2 / Vs), but no interaction between a prototype detector and an alpha particle bombardment was observed. Thus, the flux growth method is viable for growing large B[subscript]12As[subscript]2 crystals, but the impurity concentrations remain a problem.

Call number: LD2668 .T4 1948 S65 / Master of Science

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