Radon is a naturally occurring radioactive element in the 238U decay series that is found in high concentrations in certain geological formations such as Caves. Exposure to high concentrations of radon has been positively linked to the incidence<br /> of lung cancer. This study used Electret ion chambers and the RAD7 continuous radon monitor to measure radon concentrations in the Cango Caves in the Western Cape Province, South Africa. Measurements were taken during summer i.e. February 2004 and March 2005. The results for the radon activity concentrations range from the minimum of<br /> about 800 Bq.m-3 to a maximum of 2600 Bq.m-3. The two techniques give very similar results, though the Electret ion chamber results appear to be consistently higher by a few percent where measurements were taken at the same locations. A<br /> mathematical model has been developed to investigate the radon concentrations in the Cave. Diffusion and ventilation have been considered as mechanisms for explaining the distribution of radon concentrations. The ventilation rate in the Cave has been estimated under certain assumptions, and it is found to be about 7 &times / 10&minus / 6 s&minus / 1 for the Van Zyl hall which is the first large chamber in the Cave. The radon concentration increases as one goes deeper into the Cave, but then becomes fairly constant for the deeper parts. The annual effective dose that the guides are exposed to in the Cave as a result of the radon concentrations, depends strongly on the time that they spend in the Cave and in which, halls they spend most of their time in the Cave. The initial results indicate an annual effective dose of 4-10 mSv, but this needs to be further investigated.

Beryllium-7 is a cosmogenic radionuclide produced in the atmosphere through the spallation of nitrogen and oxygen nuclei by cosmic-ray-produced neutrons and protons. It is carried in the atmosphere attached to aerosols and is deposited on land and ocean surfaces by wet and dry deposition processes. Beryllium-7 decays by electron capture to lithium-7 and has a half-life of approximately 53 days. It is a potentially useful radionuclide for studying different natural processes. This thesis presents a collection of scientific papers on the occurrence of beryllium-7 in the natural environment, particularly in the Southeast Queensland region of Australia. It shows the results of experimental measurements and discusses their implications. Overall, this thesis contributes to advancing our understanding of the distribution and behaviour of beryllium-7 in the natural environment and provides a foundation for the development of nuclear techniques for the evaluation of environmental problems.

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O presente trabalho relata a implementação de um projeto de ensino, referenciado na teoria da aprendizagem significativa e no sócio-interacionismo, em uma turma de segundo módulo do curso de Licenciatura em Ciências da Natureza com Habilitação em Física do Instituto Federal de Santa Catarina. Os alunos foram engajados em um programa de produção textual para publicação de inserções radiofônicas de curta duração e na construção de um blog para a Internet sobre radioatividade e energia nuclear, tema estudado na unidade curricular de Princípios da Ciência II. Para o planejamento e construção dos textos, os alunos foram subsidiados por conteúdos sobre divulgação científica, teorias de aprendizagem, epistemologia e história da ciência, resultado da integração de outras duas unidades curriculares: Português II e Epistemologia e História das Ciências. Como material de apoio para as atividades realizadas por estes estudantes foi construído um site com textos, imagens, vídeos e mapas conceituais apresentados em aula como organizadores prévios. O objetivo do projeto consiste na compreensão dos conteúdos das unidades curriculares envolvidas e da aprendizagem significativa como referencial de ensino passível de aplicação na divulgação científica. O conteúdo dos textos produzidos pelos alunos para o rádio e para a internet, assim como os questionários aplicados antes e depois da implementação do projeto, mostraram uma apropriação de princípios e estratégias da aprendizagem significativa, dos referenciais de divulgação científica e do conhecimento científico relacionado ao tema radioatividade e energia nuclear. / This work describes the implementation, within the Instituto Federal de Educação of Santa Catarina – IFSC, of a teaching project, based on the socio-interactionism and in the meaningful learning theory, with students of the Nature Sciences major in Physics. The students engaged in a text production program to produce short-term radio broadcasts, as well as in the creation of a blog about radioactivity and nuclear energy, matter studied in the subject of Principles of Science II. In planning and in writing those texts, students relied on scientific popularization matters, learning theories, epistemology and history of science, what was a result of the integration with the Portuguese II, Epistemology, and History of Science Subjects. As a supporting material, for the activities carried out by the students, a website with texts, imagery, videos and conceptual maps presented in classes as previous organizers has been created. The project aims at the comprehension of the matters broached in the subjects involved in the course curriculum and at the meaningful learning as reference for a possible way of teaching and scientific popularization. The content of the texts produced by the students for the radio and for the Internet, as well as the questionnaires applied before and after the project development showed an appropriation of the principles and meaningful learning strategies, of the scientific popularization references and of the scientific knowledge related to the radioactivity and nuclear energy themes.

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Made available in DSpace on 2014-10-09T12:27:58Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:54Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:42:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:03Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Made available in DSpace on 2014-10-09T12:55:26Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:56Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP