Sistemas multiplicativos subcríticos foram, por muito tempo, pouco estudados, de modo que sua descrição teórica permanece com muitas questões em aberto. A presente Tese apresenta o um reatímetro subcrítico, um software desenvolvido em LabVIEWTM capaz de medir as mudanças no fluxo de nêutrons em regime subcrítico e de transformar este sinal em reatividade. A principal vantagem de um dispositivo como este é aumento da precisão das medidas de reatividade. É sabido que reatímetros convencionais não são capazes de operar em regime subcrítico nem de descrever a dinâmica de sistemas multiplicativos nessas condições, pela própria estrutura das equações de cinética pontual clássicas em que são baseados. Diversas teorias têm sido propostas para descrever a física de sistemas subcríticos, no entanto, a maior parte envolve parâmetros extremamente complexos para serem aplicados em situações práticas. A teoria de Gandini difere das outras por ser baseada em parâmetros simples, o que a torna a escolha mais conveniente para o desenvolvimento de um reatímetro subcrítico e suas aplicações. Desta maneira, o reatímetro subcrítico desenvolvido é baseado na teoria de cinética de sistemas subcríticos de Gandini e em resultados experimentais, de altíssima qualidade e relevância, alcançados no próprio IPEN/MB-01. Deve-se destacar que a aplicação de equações de cinética específicas para sistemas subcríticos é um fato inédito no desenvolvimento de reatímetros e apenas desta maneira a reatividade pode ser estimada com precisão neste regime. O presente estudo é especialmente focado na aplicação em reatores de fissão, o qual poderá se utilizado em inúmeros experimentos em reatores de pesquisa. Portanto, o presente trabalho tem relevância tanto teórica quanto prática, já que discute um ponto fundamental da física de reatores nucleares. / Multiplying subcritical systems were for a long time, poorly studied, and its theoretical description remains with plenty open questions. This Thesis presents a subcritical reactivity meter, a software developed in LabVIEWTM capable of measuring changes in neutron flux in subcritical regime and to transform this signal into reactivity. The main advantage of such device is the increase in accuracy of reactivity measurements. It is known that conventional reactivity meters cannot operate in subcritical regime nor describe the dynamics of multiplying systems under these conditions by the very structure of classical point kinetics equations. Many theories have been proposed to describe subcritical systems but most involve very complex parameters to be applied in practical situations. Gandini\'s theory differs from others by being based on simple parameters, being considered the most convenient choice to be made for the development of a reactivity meter and its applications. The developed subcritical reactivity meter was based on the Gandini\'s subcritical kinetic theory and on experimental results, of high quality and relevance, achieved at the IPEN/MB-01 reactor. It should be highlighted that the utilization of specific kinetic equations for subcritical systems is an unprecedented event in the development of reactivity meters and only by this manner the reactivity can be precisely estimated in this regime. The present study is mainly addressed to fission reactors, and it could be employed in numerous experiments in research reactors. Therefore, this work has a theoretical and practical relevance, since it discusses a fundamental point of the nuclear reactor physics.

Sistemas multiplicativos subcríticos foram, por muito tempo, pouco estudados, de modo que sua descrição teórica permanece com muitas questões em aberto. A presente Tese apresenta o um reatímetro subcrítico, um software desenvolvido em LabVIEWTM capaz de medir as mudanças no fluxo de nêutrons em regime subcrítico e de transformar este sinal em reatividade. A principal vantagem de um dispositivo como este é aumento da precisão das medidas de reatividade. É sabido que reatímetros convencionais não são capazes de operar em regime subcrítico nem de descrever a dinâmica de sistemas multiplicativos nessas condições, pela própria estrutura das equações de cinética pontual clássicas em que são baseados. Diversas teorias têm sido propostas para descrever a física de sistemas subcríticos, no entanto, a maior parte envolve parâmetros extremamente complexos para serem aplicados em situações práticas. A teoria de Gandini difere das outras por ser baseada em parâmetros simples, o que a torna a escolha mais conveniente para o desenvolvimento de um reatímetro subcrítico e suas aplicações. Desta maneira, o reatímetro subcrítico desenvolvido é baseado na teoria de cinética de sistemas subcríticos de Gandini e em resultados experimentais, de altíssima qualidade e relevância, alcançados no próprio IPEN/MB-01. Deve-se destacar que a aplicação de equações de cinética específicas para sistemas subcríticos é um fato inédito no desenvolvimento de reatímetros e apenas desta maneira a reatividade pode ser estimada com precisão neste regime. O presente estudo é especialmente focado na aplicação em reatores de fissão, o qual poderá se utilizado em inúmeros experimentos em reatores de pesquisa. Portanto, o presente trabalho tem relevância tanto teórica quanto prática, já que discute um ponto fundamental da física de reatores nucleares. / Multiplying subcritical systems were for a long time, poorly studied, and its theoretical description remains with plenty open questions. This Thesis presents a subcritical reactivity meter, a software developed in LabVIEWTM capable of measuring changes in neutron flux in subcritical regime and to transform this signal into reactivity. The main advantage of such device is the increase in accuracy of reactivity measurements. It is known that conventional reactivity meters cannot operate in subcritical regime nor describe the dynamics of multiplying systems under these conditions by the very structure of classical point kinetics equations. Many theories have been proposed to describe subcritical systems but most involve very complex parameters to be applied in practical situations. Gandini\'s theory differs from others by being based on simple parameters, being considered the most convenient choice to be made for the development of a reactivity meter and its applications. The developed subcritical reactivity meter was based on the Gandini\'s subcritical kinetic theory and on experimental results, of high quality and relevance, achieved at the IPEN/MB-01 reactor. It should be highlighted that the utilization of specific kinetic equations for subcritical systems is an unprecedented event in the development of reactivity meters and only by this manner the reactivity can be precisely estimated in this regime. The present study is mainly addressed to fission reactors, and it could be employed in numerous experiments in research reactors. Therefore, this work has a theoretical and practical relevance, since it discusses a fundamental point of the nuclear reactor physics.

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第23558号 / 地環博第215号 / 新制||地環||41(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 梶井 克純, 准教授 田中 周平, 准教授 上田 佳代 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第20038号 / 地環博第154号 / 新制||地環||31(附属図書館) / 33134 / 京都大学大学院地球環境学舎環境マネジメント専攻 / (主査)教授 梶井 克純, 准教授 真常 仁志, 准教授 田中 周平 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

The reaction of the model compound hexachlorocyclotriphosphazene (N₃P₃Cl₆) with various organometallic reagents have been studied in some detail. These reactions are quite complex yielding substitution products as well as degradation products. The reaction of alkyl Grignard reagents, in the presence of a copper complex ((n-Bu₃PCuI)₄), have been studied and produce good yields of mono- and di-alkylated chlorocyclotriphosphazenes. This method is limited in that higher substitution products can not be obtained. The reaction of trimethylaluminum (TMA) with (N₃P₃Cl₆) was examined and found to yield the fully substituted hexamethylcyclotriphosphazene (N₃P₃(CH₃)₆) in modest yield (40 %). The study of this reaction, with respect to time allowed for the determination of the substitution pathway and the preparation of two new methylated chlorocyclotriphosphazenes. It was then possible to prepare a nearly complete set of methylated chlorocyclotriphosphazenes (N₃P₃(CH₃)_nCl_6-n) using this method and the Grignard route. The reactions of other alkylaluminum reagents were also examined and are discussed. The effects of the complexation of TMA with the homologous series was next examined using ¹H, and ³¹P NMR. The results for these investigations indicate that the overall electron donating ablity of the phosphazene ring increased with increasing methyl substitution. Variable temperature NMR studies allowed for the determination of the sites of complexation and their relative strengths with respect to the number of methyl groups on the phosphazene ring. / Ph. D. / incomplete_metadata

The reactions of methyl-substituted chlorocyclotriphosphazenes with aryl Grignard reagents and with bifunctional amines, aminoalcohols, and alkoxides were investigated. The characterization data for the compounds formed in the reactions of monomethylpentachlorocyclotriphosphazene and the Grignard reagents were found to be informative with respect to the extent and nature of the interaction between the phosphazene ring and its exocyclic substituents. This interaction was found to be responsible for significant effects on the reactions of the phosphazene ring with nucleophiles. The reactions of the bifunctional nucleophiles were found to be useful probes of the reactivity of the phosphazene ring. Specifically, a single methyl group is found to activate the chlorine on the same phosphorus atom, while a pair of geminally substituted methyl groups is found to deactivate the chlorine atoms on a different phosphorus atom. The results allow a new interpretation of the substitution patterns of various nucleophiles on chlorocyclotriphosphazenes. / Ph. D. / incomplete_metadata

The acld-oata17zed oyclodehydrat1on reaction of 2-benzylphenyl l-naphthyl ketone gives two products! 9-(1-naphthyl)anthracene, the expected product and in addition lO-phenyl-l,2-benzanthracene. This second product is the one expected it the ketone were subjected to the conditions of an .Elba reaction. The effect of substituents on the course of this reaction was investigated by synthesizing six 2-benzylphenyl 1- and 2-naphthyl ketones and subjecting each of them to the acid catalyzed reaction and to Elba reaction conditions. Of the six ketones, two had unsubstituted benzyl groups, two had 3'-methyl groups in the benzyl group and the remaining two had ,'-tr1fluoromethyl groups. The original finding was confirmed and the other ketones that cyoilzed by either treatment gave the expected products. When 2-(3'-methylbenzyl) 2-naphthl1 ketone was subjected to Elbs reaction conditions, 9-(2-naphthyl)anthraoene, the product of aromatic oyclodehydrat1on, was obtained. An explanation oft the unusual experimental results is suggested. The results of treat1ng the ketones w1th alumina and w1th l1qu1d hydrogen fluoride are reported. / Ph. D.

The relative reactivities of pulverized samples (100-200 mesh) of 3 marcasite and 7 pyrite specimens from various sources were determined at 25°C and pH = 2.0 in ferric chloride solutions with initial ferric iron concentrations of 10⁻³ molal. The rate of the reaction: FeS₂ + 14Fe³⁺ + 8H₂O = 15Fe²⁺ + 2SO₄²⁻ + 16H⁺ was determined by calculating the rate of reduction of aqueous ferric ion from measured oxidation-reduction potentials. The reaction follows the rate law: -d m_Fe³⁺ / dt = k (A/M) m_Fe³⁺ where m_Fe³⁺ is the molal concentration of uncomplexed ferric iron, k is the rate constant and A/M is the surface area of reacting solid to mass of solution ratio. The measured rate constants, k, range from 1.0x10⁻⁴ to 2.7x10⁻⁴ sec⁻¹ ±5%, with lower-temperature/early diagenetic pyrite having the smallest rate constants, marcasite intermediate, and pyrite of higher-temperature hydrothermal and metamorphic origin having the greatest rate constants. Geologically, these small relative differences between the rate constants are not significant, so the fundamental reactivities of marcasite and pyrite are not appreciably different. The activation energy of the reaction for a hydrothermal pyrite in the temperature interval of 25 to 50°C is 92 kJ mol⁻¹. The BET-measured specific surface area for lower-temperature/ early diagenetic pyrite is an order of magnitude greater than that for pyrite of higher-temperature origin. Consequently, since the lower-temperature types have a much greater A/M ratio, they will appear to be more reactive per unit mass than the higher temperature types. / Master of Science

Ion exchange and precipitation technologies were examined for the selective separation and recovery of silver and mercury from COD waste solutions. Batch equilibrium studies were conducted to determine ion exchange selectivity of several commercial and regenerated resins. Resin capacity and metal ion recovery efficiency were evaluated in continuous-flow column studies. Solubility studies were included to determine if metal ions could be selectively separated and included in a treatment regime for removal and recovery of silver and mercury from the waste solution. Reduction of waste volume was also an important consideration for precipitation of metal ions. The results indicated that ionic strength considerations dictate overall treatment and recovery efficiency. Silver and mercury ions were removed by ion exchange while iron and chromium uptake did not occur. Highest removal efficiencies were observed for a mercury-specific resin and an anionic resin compared to cationic or mixed resins. Column capacity was severely impacted by the acidic, high strength, waste solution. Additional studies showed that the solution ionic strength and dissolved solids concentration were more important than solution pH in determining ion exchange preference and column capacity. Reuse of column regenerant solutions in the COD test procedure indicated the strength of sulfuric acid was critical in obtaining complete oxidation of a synthetic waste solution. / M.S.

The oxidation of arsenic (III) by chromium (VI) has been studied in pyridine - pyridinium buffers with and without added oxalate ion. The rate law at pH 4.6 for the reactions without oxalate is best described as - d[Cr(VI)]/dt = (0.535 [As(III)]² [Cr(VI)])/(1+187 [As(III)]) This is in accord with the general mechanism for chromium (VI) oxidation proposed by Beattie and Haight. The behavior in pyridine - pyridinium buffers is different from that observed in acetic acid acetate buffers of the same pH. In the presence of oxalate, the observed rate law is - d[Cr(VI)]/dt = (310 [As(III)] [C₂O₄²⁻] [Cr(VI)])/(1+31.0 [As(III)]) In each case the reaction stoichiometry was found to be 3As(III) + 2Cr(VI) = 3As(V) + 2Cr(III). The role of oxalate was found to be catalytic although it was incorporated in the final Cr(III) product. Complex kinetic behavior was observed as a function of pH, [AsIII], and buffer composition. / M.S.