<p>This thesis aims to measure the rate of radon loss from water in a systematic way. The dependence on surface area, temperature and concentration will be investigated. The experiments were done at UWC by creating radon using radium sources and then measuring the radon concentrations inside a vacuum chamber to obtain the speed of radon escape from the water. The results are compared to a model [Cal 2002] where the radon concentration in the air and hence the transfer rate is measured using a RAD7 radon detector. Since the equations cannot be solved analytically, a numerical solution is employed. The radon transfer velocity coefficient is found to be (1.9&plusmn / 0.5)&times / 10-6m/s. This value indicates that the escape of radon should not be a problem when a sample is open to the air for a minute or two.</p>

<p>This thesis aims to measure the rate of radon loss from water in a systematic way. The dependence on surface area, temperature and concentration will be investigated. The experiments were done at UWC by creating radon using radium sources and then measuring the radon concentrations inside a vacuum chamber to obtain the speed of radon escape from the water. The results are compared to a model [Cal 2002] where the radon concentration in the air and hence the transfer rate is measured using a RAD7 radon detector. Since the equations cannot be solved analytically, a numerical solution is employed. The radon transfer velocity coefficient is found to be (1.9&plusmn / 0.5)&times / 10-6m/s. This value indicates that the escape of radon should not be a problem when a sample is open to the air for a minute or two.</p>

Orientador: Julio Cesar Hadler Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-26T04:48:46Z (GMT). No. of bitstreams: 1 Pereira_LucasAntoniassi_M.pdf: 1401742 bytes, checksum: e450c67acc972690e5fca996ffceb006 (MD5) Previous issue date: 2014 / Resumo: A medida da atividade de radônio (222Rn) no ar ambiental tem sido feita intensamente nas últimas quatro décadas, pelo fato de ser este o contaminante natural mais importante a que o homem está sujeito. Sabe-se que os filhos do 222Rn são os verdadeiros contaminantes a serem considerados no caso da contaminação de ambientes internos por radônio, no entanto ainda não há uma metodologia robusta para a medida passiva da concentração de atividade dos filhos no ar. Resultados anteriores do Grupo de Cronologia da Unicamp apontam que a utilização de detectores CR-39 de tamanhos reduzidos se apresentam como possível alternativa na investigação da concentração dos produtos de decaimento do 222Rn no ar. Nesse sentido, conjuntos com detectores de traços nucleares CR-39 de diversos tamanhos foram expostos no interior de ambientes fechados e de pouca ventilação, longe de qualquer superfície material. As exposições ocorreram em duas etapas: conjuntos com 6 detectores foram expostos durante cerca de 7 meses em 14 ambientes, e conjuntos com 10 detectores foram novamente expostos durante aproximadamente 5 meses em 3 destes locais. Observou-se que a densidade de traços nos detectores foi tanto maior quanto menor o tamanho do detector. Dados de densidade de traços foram ajustados utilizando-se uma equação deduzida com base no pressuposto de que o comportamento dos átomos dos filhos do radônio no ar pode ser descrito pela Lei de Fick, ou seja, o principal mecanismo de transporte dessas partículas no ar é a difusão. Considerou-se também o fenômeno da deposição (plate-out) dos filhos do radônio (livres ou ligados em aerossóis) em superfícies dos ambientes, incluindo as dos detectores. A atividade de radônio no ar foi determinada de maneira independente pela técnica do monitor NRPB/SSI. A equação resultante para a densidade de traços nos detectores das montagens expostas nos vários ambientes foi ajustada aos resultados experimentais. Observou-se, de fato, que na maioria dos ambientes pouco ventilados vale a lei de Fick, o que significa que radônio e filhos estariam em equilíbrio de atividades. Este resultado, se confirmado com mais dados experimentais, é importante por duas razões: i) porque é raro se fazer medidas conjuntas de radônio e filhos em exposições longas, e ii) porque ambientes de convívio humano pouco ventilados são comumente usados. Porém, a quantificação destes ajustes precisa ser aprimorada, tanto no que diz respeito a testes estatísticos como simulação computacional / Abstract: Radon activity in indoor environments has been intensively studied in the last four decades, probably because it is the main natural contamination to which man is subjected. It is well known that radon daughters are in fact the true contaminants. However, there is not yet a robust and accepted methodology for measuring radon progeny activity in the air passively. Previous results obtained by the Chronology Group of Unicamp show that the use of CR-39 detectors in reduced sizes may be an alternative to investigate the radon progeny concentration in the air. In this sense, sets of CR-39 nuclear track detectors of different sizes were exposed in poor ventilated indoor environments, far from any material surfaces. The exposures occurred in two steps: sets with 6 detectors were exposed during 7 months in 14 environments, and sets with 10 detectors were again exposed during approximately 5 months in 3 of these same places. It was observed that track density was as greater as smaller was the detector¿s size. Alpha particle track densities were fitted against an equation deduced based on the assumption that the behavior of radon progeny in the air was described by Fick¿s Law, i.e., the main transport mechanism of these particles was diffusion. It was also considered the deposition phenomenon (plate-out) of radon progeny (free or attached to aerosols) on environmental surfaces, including the detector themselves. Radon activity in the air was determined independently by NRPB/SSI monitor technique. The resulting equation for the track density was fitted to the experimental track densities measured on each exposed set of detectors. It was observed, indeed, that in most of the poor ventilated environments the Fick¿s law was valid under ?2 test, which means that radon and its progeny would be in equilibrium of activities. If, confirmed with more experimental data, these results are important for two reasons: i) because results of simultaneous measures of radon and progeny for long term expositions are rare, and ii) because poorly ventilated indoor environments are commonly used all over the world. However, these fittings quantification needs improvement, both regarding statistical tests and computer simulations / Mestrado / Física / Mestre em Física

Magister Scientiae - MSc / This thesis aims to measure the rate of radon loss from water in a systematic way. The dependence on surface area, temperature and concentration will be investigated. The experiments were done at UWC by creating radon using radium sources and then measuring the radon concentrations inside a vacuum chamber to obtain the speed of radon escape from the water. The results are compared to a model [Cal 2002] where the radon concentration in the air and hence the transfer rate is measured using a RAD7 radon detector. Since the equations cannot be solved analytically, a numerical solution is employed. The radon transfer velocity coefficient is found to be (1.9±0.5)×10-6m/s. This value indicates that the escape of radon should not be a problem when a sample is open to the air for a minute or two. / South Africa

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