Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 142-153).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Made available in DSpace on 2014-10-09T12:46:33Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:30Z (GMT). No. of bitstreams: 1 07966.pdf: 4481327 bytes, checksum: ae11c93769fa67fceb5ed128248bcacb (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:00/00516-7

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In-vessel tungsten components of a future demonstration fusion reactor are likely to be operated in the material's non-ductile regime. Assessment of the components' reliability is not possible with current ductile design codes or through experimental qualification. There is therefore an urgent need for non-ductile assessment procedures. One such approach currently considered is Weibull's weakest link theory, which is based on linear-elastic fracture mechanics and has its origins in ceramics. A full assessment of its validity has been performed, and the challenge of obtaining irradiated material data addressed. Bend tests at the macroscopic scale confirm previous findings that the scatter in strength of pure tungsten follows a two-parameter Weibull distribution, provided the material fractures within its elastic regime. However, tests conducted over a range of specimen sizes reveal the technique's shortcomings in accurately predicting the material's size effect in fracture, questioning its applicability to pure tungsten and also other brittle metallic materials. Fracture strength tests conducted at the micrometre scale through cantilever bending have addressed the challenge of obtaining irradiated material data. An ultra-fine grained self-passivating tungsten alloy, considered as an alternative contender to tungsten for in-vessel components, is shown to fracture within its linear-elastic regime at the microscopic scale. A reliable and repeatable measurement of its strength of approximately 5.9 GPa is obtained. The scatter in measurements is shown to be greater than random errors, and to be described well by a two-parameter Weibull distribution. Cantilever tests conducted over a range of specimen sizes reveal a strong size effect (4.3 - 9.0 GPa), which is accurately predicted by Weibull's weakest link theory. Ion implantations, conducted in the tungsten alloy to mimic neutron induced elastic collision damage, result in a statistically confirmed drop (6 %) in cantilever measured fracture strength at low doses (0.7 dpa), and an increase (9-16 %) at higher doses (7 dpa).The cantilever test technique is therefore suitable for the measurement of ion and neutron irradiation effects on the material's fracture strength. Provided a full validation of Weibull's weakest link theory strength extrapolation from the micro- to macroscopic scale is realised on a future heterogeneity free material batch, irradiated material data obtained from cantilever tests could be used to assess the reliability of in-vessel components fabricated from a self-passivating tungsten alloy, and fill the current gap in non-ductile design assessment procedures.

Made available in DSpace on 2014-06-11T19:31:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-16Bitstream added on 2014-06-13T19:41:49Z : No. of bitstreams: 1 oliveirajunior_b_dr_botfm.pdf: 616970 bytes, checksum: 156878e124f2d8e1dc946e551816e468 (MD5) / Universidade Estadual Paulista (UNESP) / Existem diversas modalidades de tratamento para queloides que isoladamente apresentam resultados desapontadores. O tratamento combinado de excisão cirúrgica e irradiação pós-operatória com elétrons é efetiva para a qualidade da cicatriz e redução da taxa de recidiva. Avaliar comparativamente dois esquemas de tratamento utilizando feixes de elétrons em termos de probabilidade de cura e efeitos colaterais na área irradiada. Este é um estudo clínico, fase III, prospectivo, randomizado, realizado na Faculdade de Medicina de Botucatu-UNESP, no período 2008 a 2010, incluindo pacientes, no pós-operatório imediato de ressecção de queloides, divididos nos grupos G1 e G2 que receberam tratamento radioterápico com elétrons de um Acelerador Linear, 30 Gy/10 frações para G1 e 32 Gy/16 frações para G2. O seguimento foi de 18 meses. Os resultados foram avaliados através de observação feita por dois avaliadores independentes e questionário aplicado aos participantes do estudo. Fizeram parte do estudo 43 pacientes, 21 no grupo G1 e 22 no grupo G2. No grupo G1 52,4%% apresentaram bons resultados e 47,6% de recidivas. No grupo G2, 91% de bons resultados e 9% de recidivas. O esquema 32 Gy/16 frações e superior ao esquema 30 Gy/10 frações, com melhor resposta terapêutica e menos efeitos colaterais / There are many different treatments for keloids that alone show disappointing results. The combined treatment of surgical excision and irradiation post- operative with electrons is effective for the quality of the scar and reduction of the rate of recurrence. To compare two treatments using different quantity of electron beams in terms of the probability of cure and side effects in the area irradiated. This is a clinical study, fase III, prospective, randomized, carried out at the Faculdade de Medicina de Botucatu, UNESP, in the period 2008 to 2010, including patients, in the immediate postoperative period of resection of keloids, divided in G1 and G2. Patients received radiotherapy with electrons of a Linear Accelerator, 30 Gy/10 fractions for G1 and 32 Gy/16 fractions for G2. The follow-up was 18 months. The results were assessed by means of observation made by two independent evaluators and the questionnaire applied to participants of the study. The study involved 43 patients, 21 in group G1 and 22 in group G2. In group G1 52.4 %% showed good results and 47.6 % of relapses. In group G2, 91% of good results and 9% of relapses. The scheme 32 Gy/16 fractions showed better response to treatment and less side effects

Dentre as diversas aplicações dos radioisótopos, a utilização dos radiotraçadores é considerada uma das mais importantes, no diagnóstico de funcionamento dos equipamentos de processos, em plantas de indústrias químicas e petroquímicas. Os radiotraçadores são utilizados em procedimentos analíticos para obtenção de dados qualitativos e quantitativos de sistemas, em estudos de transferências físicas e físico-químicas. Na produção de radioisótopos gasosos utilizados como traçadores em processos industriais, destacam-se o 41Ar e 79Kr, gases nobres (inertes) que possuem baixa reatividade com os demais elementos químicos. O 41Ar é um emissor gama de alta energia (1,29 MeV) e apresenta elevada porcentagem de transformações com essa energia, o que resulta em quantidades relativamente pequenas necessárias em relação a outras para uma detecção eficaz, mesmo em componentes com grandes espessuras. Atualmente, a produção de radioisótopos gasosos em reatores nucleares de pesquisa é realizada em pequenas quantidades (bateladas), por meio de ampolas de quartzo contendo o gás natural 40Ar ou 78Kr. Nesse sentido, o objetivo desse estudo é desenvolver um sistema de irradiação capaz de produzir em escala contínua, o radioisótopo gasoso 41Ar, dentre outros, com atividade de 7,4x1011 Bq (20 Ci) por ciclo de irradiação, por meio do Reator IEA-R1 de 4,5 MW, fluxo de nêutrons térmicos médio de 4,71 x 1013 ncm-2s-1, para suprir uma demanda existente em empresas de END e inspeções, e pelo próprio Centro de Tecnologia das Radiações, no IPEN/CNEN-SP. O sistema de irradiação (SI) é constituído por uma cápsula de irradiação em alumínio, linhas de transferência, válvulas agulhas, conexões anilhadas, conectores rápidos, manovacuômetro, sistema de vácuo, dewar de liquefação, blindagem em chumbo, cilindros de armazenamento e transporte (CAT), dentre outros. O SI foi aprovado nos testes de estanqueidade e estabilidade (testes de formação de bolhas, pressurização, evacuação e com equipamento leak detector SPECTRON 600 T). Na produção experimental para obtenção de 1,07x1011 Bq (2,9 Ci) de 41Ar, distribuíram-se dosímetros de alanina em diversos componentes e dispositivos do SI. Além disso, determinaram-se as taxas de exposição na parede da blindagem em chumbo, ao concentrar o gás radioativo liquefeito e no CAT, após a transferência do 41Ar, pelo medidor de radiação portátil Teletector ® Probe 6150 AD-t/H. / Among the various applications of radioisotopes, the use of radiotracers is considered the most important in diagnosing operation and troubleshooting of industrial process plants in chemical and petrochemical companies. The radiotracers are used in analytical procedures to obtain qualitative and quantitative data systems, in physical and physicochemical studies transfers. In the production of gaseous radioisotopes used as tracers in industrial process measurements, argon-41 (41Ar) and krypton-79 (79Kr) have low reactivity with other chemical elements. 41Ar is a transmitter range with high-energy (1.29MeV) and a high percentage of this energy transformation (99.1%), resulting in relatively small quantities required in relation to the other, for an efficient detection, even in large thicknesses components. Nowadays, the production of gaseous radioisotopes in nuclear research reactors is performed in small quantities (batches), through quartz ampoules containing natural gas 40Ar or 78Kr. In this sense, the aim of this study is to develop an irradiation system for gaseous radioisotope production in continuous scale, applied in industrial applications of emission tomography and flow measurement. The irradiation system may produce 41Ar with activity of 7.4x1011Bq (20Ci) per irradiation cycle, through the Reactor IEA-R1 with 4.5MW and average thermal neutron flux of 4.71x1013 ncm-2s-1 to meet an existing demand in NDT and inspections companies, and even needed by the Radiation Technology Centre, at IPEN/CNEN-SP. The irradiation system consists of an aluminium irradiation capsule, transfer lines, needle valves, stripy connections, quick connectors, manometer, vacuum system, dewar, lead shielding, storage and transport cylinders, among other components. The irradiation system was approved in the leakage and stability tests (bubble test, pressurization, evacuation and with leak detector equipment SPECTRON 600 T). In the experimental production, alanine dosimeters were distributed into various components of the irradiation system, obtaining 1.07x1011Bq (2.9Ci) of 41Ar. In addition, exposure rates were determined in the lead shielding wall, in which the liquefied radioactive gas was concentrated, and in the storage and transport cylinders after 41Ar was transferred, by the portable radiation meter Teletector ® Probe 6150 AD-t/H.

Made available in DSpace on 2014-10-09T12:53:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:31Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP / FAPESP:05/52055-7

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