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AbstractAbstract
[en] In order to increase safety during the long-term storage of Kr-85 it has been proposed to encaosulate this gas in zeolite 5A. Due to the decay heat of Kr-85 it is expected, however, that the inorganic matrix will be at an increased temperature over several decades. Below 6000C only very small Kr-desorption rates are observed when a linear temperature gradient is applied to a loaded 5A zeolite sample. If heating is interrupted and the temperature kept konstant at a certain value (>6000C), it is observed that the desorption rate either decreased below the detection limit or stayed constant at some measurable value. The overall activation energy in the temperature range 5700C-7450C is found to be 250 kJ/mol. At temperature above 7900C the total encapsulated gas is rapidly liberated. No significant leakage was apparent from zeolite 5A samples containing between 19 and 57 cm3 STP Kr/g kept at 2000C for up to 2500 h and 4000C for up to 3500 h. From these studies it is found that type 5A zeolites are particularly suitable as a matrix for the inmobilization of Kr-85. (Author)
[pt]
Para aumentar a seguranca durante o longo periodo de armazenamento do Kr-85, propoe-se o armazenamento desse gas em zeolitos tipo 5A. Devido ao calor originado pelo decaimento radioativo do Kr-85, espera-se um aumento de temperatura na matriz inorganica por varias decadas. Abaixo de 6000C encontram-se somente pequenas taxas de desorcao do Criptonio quando aplica-se um gradiente linear de temperatura na amostra zeolitica 5A. Se o aquecimento e interrompido e a temperatura tomada constante a um certo valor (>6000C), observa-se que a taxa de desorcao decresce ate abaixo do limite de deteccao ou permanece constante num valor mensuravel. Encontra-se o valor de 250 KJ/mol para a energia de ativacao total num alcance de temperatura entre 570-7450C. Em temperatura acima de 7900C, todo o gas encapsulado e rapidamente liberado. Nenhuma fuga significante de amostra zeolitica 5A e encontrada, as quais possuem cargas entre 19 e 57 Ncm3Kr/grama de zeolito, guardadas a 200C por mais de 2500 horas e a 4000C por mais de 3500 horas. A partir destes experimentos aparece o zeolito tipo 5A como matriz propicia a fixacao do Kr-85. (Autor)Original Title
Fixacao de gases nobres em zeolitos
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Sep 1980; 98 p; Tese (M.Sc.).
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Miscellaneous
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Thesis/Dissertation
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