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Universiẗat, Diss., 1999--Tübingen.

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Made available in DSpace on 2014-10-09T12:36:14Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:20Z (GMT). No. of bitstreams: 1 03765.pdf: 4268943 bytes, checksum: 1eabaa58f9bf24d34593d59bf89ff6ca (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-03-17T10:41:16Z No. of bitstreams: 0 / Made available in DSpace on 2015-03-17T10:41:16Z (GMT). No. of bitstreams: 0 / Este trabalho apresenta um novo método para o cálculo dos coecientes de sensibilidade, através da união do metodo diferencial e da teoria da perturbação generalizada, que são os dois métodos tradicionalmente utilizados em física de reatores para a obtenção de tais grandezas. Esses dois métodos apresentam algumas deciências tornando os cálculos dos coeficientes de sensibilidade lentos ou computacionalmente exaustivos, mas unindo-os e possível eliminar as deciências apresentadas por ambos e obter uma nova equação para o coe- ciente de sensibilidade. O método proposto neste trabalho foi aplicado em um reator do tipo PWR , onde foi feita análise de sensibilidade da produção e da razão de conversão do 239Pu, para um ciclo de 120 dias de queima. O código utilizado para a análise de queima e análise de sensibilidade, o CINEW, foi desenvolvido durante este trabalho e os resultados obtidos foram comparados com os códigos amplamente utilizados em física de reatores, como o CINDER e o SERPENT. As conclusões obtidas foram que o novo método matemático para a obtenção dos coeficientes de sensibilidade e o CINEW, além de fornecer agilidade numérica também presentam eciência e segurança. Pois o novo método matemático para a obtenção dos coeficientes quando comparados com os métodos tradicionais utilizados para a análise de sensibilidade, mostram resultados satisfatórios, mesmo quando o método utiliza aproximações matemáticas que diferem do método proposto, e com a vantagem de não apresentar as deciências apresentadas pelos métodos diferencial e da teoria da perturbação generalizada. As análises de queima obtidas pelo CINEW foram comparadas com o CINDER, que mostraram uma diferença aceitável, apesar do CINDER apresentar alguns problemas computacionais que advém da época em que foi feito. A originalidade deste trabalho e a aplicação do método proposto em problemas que envolvem dependência temporal e a elaboração do primerio código nacional que faz análise de queima e análise de sensibilidade. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Methods for the determination of the actinide elements in water, biological, soil and sediment samples have been developed using on-line solid phase extraction and high performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS). Initial applications utilised a commercially available resin, namely TRU-Spec resin, for efficient removal of the matrix prior to elution of uranium and thorium analytes. Comparative analyses of reference materials and natural water samples from Plymouth and Dartmoor demonstrated significant improvement in precision and speed of analysis by using TRU-Spec coupled to ICP-MS compared with alpha spectrometry. Further applications of the TRU-Spec resin for the determination of the transuranic actinide elements neptunium, plutonium and americium, resulted in the successful determination of 239Pu and 237Np in biological reference materials. Detection limits were 700, 850, and 600 attograms (ag) for 237Np, 233Pu, and 241Am, respectively, for a 0.5 ml sample injection, and better than 200 ag/g with 50 ml pre-concentration when sector field (SF) ICP-MS was used. A method for the selective sequential elution of uranium and plutonium was also developed to facilitate the determination of 239Pu without interference due to the 238U1H+ polyatomic ion, caused by high concentrations of 238U in sediment samples. Investigations were performed into the use of a polymeric substrate, which was dynamically coated with chelating dyes such as xylenol orange and 4-(2-pyridylazo) resorcinol, and a silica substrate coated with permanently bonded iminodiacetic acid. The latter was used for the successful determination of uranium and thorium in certified reference material waters. However, the column was found to have a high affinity for iron, making it unsuitable for the determination of the actinides in soil and sediment samples. Subsequently, a polystyrene substrate which was dynamically coated with dipicolinic acid was used for HPLC coupled with SF-ICP-MS. Using this column it was possible to separate the various actinides from each other and from the matrix. In particular, it was possible to separate plutonium and uranium to facilitate interference-free determination of the former. The column also exhibited some selectivity for different oxidation states of Np, Pu and U. Two oxidation states each for plutonium and neptunium were found, tentatively identified as Np(V) and Pu(III) eluting at the solvent front, and Np(IV) and Pu(IV) eluting much later. Detection limits were 12, 8, and 4 fg for 237Np, 239Pu, and 241Am, respectively, for a 0.5 ml injection, and the system was successfully used for the determination of 239Pu in water, biological and soil reference materials.

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Made available in DSpace on 2014-10-09T12:44:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:12Z (GMT). No. of bitstreams: 1 06901.pdf: 9310315 bytes, checksum: 34ec97737bf373b58a295f330b6aa935 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP