No description available.

Made available in DSpace on 2014-10-09T12:38:10Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:50Z (GMT). No. of bitstreams: 1 05651.pdf: 5599024 bytes, checksum: 2673b4e5195ce313cc827fb7eadc9a2c (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:38:10Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:50Z (GMT). No. of bitstreams: 1 05651.pdf: 5599024 bytes, checksum: 2673b4e5195ce313cc827fb7eadc9a2c (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:55:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:02Z (GMT). No. of bitstreams: 1 12872.pdf: 4266706 bytes, checksum: b6331850536761ebbc6e3514d66acac9 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:55:05Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:02Z (GMT). No. of bitstreams: 1 12872.pdf: 4266706 bytes, checksum: b6331850536761ebbc6e3514d66acac9 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Die Endlagerbranche steht vor einem tiefgreifenden Wechsel. Die bisherigen Organisationseinheiten DBE mbH, ASSE GmbH, Bundesamt für Strahlenschutz (BfS) werden neu sortiert und in der neugegründeten Bundes-Gesellschaft für Endlagerung verschmolzen. Eine neue Genehmigungsbehörde, das Bundesamt für Kerntechnische Entsorgungssicherheit (BfE) wird geschaffen. Im Ergebnis dieser Neustrukturierung gibt es eine klare Aufgabentrennung zwischen Regulator und Operator. Darüber hinaus führt die Zusammenlegung der bisher verteilten Aufgaben vom Bauherr und ausführender Baufirma zu Synergieeffekten und einer größeren Umsetzungskompetenz in den Endlagerprojekten. Die neue Bundes-Gesellschaft für Endlagerung (BGE) wird sowohl in der Tiefe als auch in der Breite ihre Aktivitäten jede der bisher bestehenden Organisationen übertreffen und daher eine höhere Schlagkraft haben.

Glassy carbon is a disordered form of carbon with very high temperature resistance, high hardness and strength and chemical stability even in extreme environments. Glassy carbon is also unaffected by nearly all acids and cannot be graphitized even at very high temperature. Because of these characteristics, there is a possibility that glassy carbon can replace copper, iron, titanium alloys and other materials employed in making canisters used in nuclear waste storage. The modification of glassy carbon due to strontium ions implantation and heat treatment is reported. Glassy carbon (GC) samples were implanted with 200 keV strontium ions to a fluence of 2×1016 ions/cm2 at room temperature. Sequential isochronal annealing was carried out on the implanted samples at temperatures ranging from 200 oC - 900 oC for one hour. The influence of ion implantation and annealing on surface topography was examined by the scanning electron microscopy (SEM), while Raman spectroscopy was used to monitor the corresponding structural changes induced in the glassy carbon. The depth profiles of the implanted strontium before and after annealing were determined using Rutherford Backscattering Spectroscopy (RBS). Compared to SRIM predictions the implanted strontium profiles was broader. After annealing at 300 oC, bulk and surface diffusion of the strontium atoms took place. Annealing at 400 oC- 700 oC not only resulted in further diffusion of strontium towards the surface, the diffusion was accompanied with segregation of strontium on the surface of the glassy carbon substrate. Evaporation of the strontium atoms was noticed when the sample was annealed at 800 oC and 900 oC respectively. These annealing temperatures are higher than the melting point of strontium (~769 oC). The Raman spectrum of the virgin glassy carbon shows the disorder (D) and graphitic (G) peaks which characterize disordered carbon materials. Merging of these two peaks was observed when the virgin sample was implanted with strontium ions. Merging of these peaks is due to damage caused by the implantation of strontium. The Raman spectrum recorded after heat treatment showed that only some of the damage due to implantation was annealed out. Annealing at 20000C for 5 hours resulted in a Raman spectrum very similar to that of virgin glassy carbon indicating that the damage due to the ion implantation was annealed out. SEM showed large differences in the surface topography of the polished glassy carbon surfaces and those of as-implanted samples. Annealing did not significantly change the surface microstructure of the implanted samples. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Physics / unrestricted

Apresentamos um estudo de solidificaçaõ e lixiviacão de matrizes de vidros porosos de alto teor de sílica armazenando 20% em peso de solução aquosa simuladora de rejeitos nucleares de alto nível de radioatividade do tipo Savanah River Labratory. A matriz porosa foi preparada após o tratamento térmico de um vidro de 65% SiO2-27%B2O3-8%Na2O, que sofreu separação de fase à 560°C por 20 horas e lixiviado em HCl - 3N à 90°C. O tamanho dos poros (tipicamente de 100 à 250Å de diâmetro) , foi determinado utilizando o método BET. Após sinterização à 1300°C em ar, as amostras foram caracterizadas física e quimicamente através de testes de lixiviação padronizados MCC1, Soxhlet (MCC5) e Estagnante durante cerca de 28 dias. Determinamos a perda de peso total, o pH, as taxas de lixiviação diferencial e as concentrações acumuladas para os seguintes elementos: Si, Na, B, Ca, Mn, Al, Fe e Ni com técnicas de ICP e espectroscopia de chama para o caso do Na. Os resultados são comparados com os obtidos com vidros borosilicatos de referência, fabricados por fusão convencional (SRL 131, PNL 76-68, MCC 76-68, SRL TDS 131, AVM-Ml à M7), vidros fabricados pela técnica sol-gel (TDS 211), vidros de alto teor de sílica (CU PGM), synroc-D, cerâmicas manufaturadas, concreto FUETAP e matrizes metálicas. Os valores obtidos são similares àqueles obtidos com os melhores vidros borosilicato presentemente usados. / We present a study of the sinterization and of the leaching behavior of a high silica porous glass matrix containing 20 weight % of simulated solution of high level liquid nuclear waste of the type Savanah River Laboratory. The porous matrix has been prepared after heat treatment of a 65% SiO2-27%B2O3-8%Na2O glass, phase separate at 560°C for 20 hours and leached in 3N HCl at 90°C. The pore size (typically 100-250Å in diameter) has been determined by the BET method. After sinterization in air at 1300°C, the samples have been physically and chemically characterized during 28 days using the MCC1, Estagnant and Soxhlet (MCC5) standard tests. We have determined thetotal weight loss, the pH, the diferential leaching rate and the cumulative concentrations for the following elements: Si, Na, B, Ca, Mn, Al, Fe and Ni by ICP technique, for Na flames spectroscopy. The results are compared with these obtained with other reference borosilicate glasses made by conventional fusion techniques (SRL 131, PNL 76-68, MCC 76-68, SRL TDS 131, AVM-M1 to M7), glasses made by sol-gel technique (TDS-211), porous glasses matrix (CU PGM), synroc-D, tailored ceramics, FUETAP concrete and metallic matrix. The values obtained are similar to those found for the best borosilicate glass presently used.

Apresentamos um estudo de solidificaçaõ e lixiviacão de matrizes de vidros porosos de alto teor de sílica armazenando 20% em peso de solução aquosa simuladora de rejeitos nucleares de alto nível de radioatividade do tipo Savanah River Labratory. A matriz porosa foi preparada após o tratamento térmico de um vidro de 65% SiO2-27%B2O3-8%Na2O, que sofreu separação de fase à 560°C por 20 horas e lixiviado em HCl - 3N à 90°C. O tamanho dos poros (tipicamente de 100 à 250Å de diâmetro) , foi determinado utilizando o método BET. Após sinterização à 1300°C em ar, as amostras foram caracterizadas física e quimicamente através de testes de lixiviação padronizados MCC1, Soxhlet (MCC5) e Estagnante durante cerca de 28 dias. Determinamos a perda de peso total, o pH, as taxas de lixiviação diferencial e as concentrações acumuladas para os seguintes elementos: Si, Na, B, Ca, Mn, Al, Fe e Ni com técnicas de ICP e espectroscopia de chama para o caso do Na. Os resultados são comparados com os obtidos com vidros borosilicatos de referência, fabricados por fusão convencional (SRL 131, PNL 76-68, MCC 76-68, SRL TDS 131, AVM-Ml à M7), vidros fabricados pela técnica sol-gel (TDS 211), vidros de alto teor de sílica (CU PGM), synroc-D, cerâmicas manufaturadas, concreto FUETAP e matrizes metálicas. Os valores obtidos são similares àqueles obtidos com os melhores vidros borosilicato presentemente usados. / We present a study of the sinterization and of the leaching behavior of a high silica porous glass matrix containing 20 weight % of simulated solution of high level liquid nuclear waste of the type Savanah River Laboratory. The porous matrix has been prepared after heat treatment of a 65% SiO2-27%B2O3-8%Na2O glass, phase separate at 560°C for 20 hours and leached in 3N HCl at 90°C. The pore size (typically 100-250Å in diameter) has been determined by the BET method. After sinterization in air at 1300°C, the samples have been physically and chemically characterized during 28 days using the MCC1, Estagnant and Soxhlet (MCC5) standard tests. We have determined thetotal weight loss, the pH, the diferential leaching rate and the cumulative concentrations for the following elements: Si, Na, B, Ca, Mn, Al, Fe and Ni by ICP technique, for Na flames spectroscopy. The results are compared with these obtained with other reference borosilicate glasses made by conventional fusion techniques (SRL 131, PNL 76-68, MCC 76-68, SRL TDS 131, AVM-M1 to M7), glasses made by sol-gel technique (TDS-211), porous glasses matrix (CU PGM), synroc-D, tailored ceramics, FUETAP concrete and metallic matrix. The values obtained are similar to those found for the best borosilicate glass presently used.

Made available in DSpace on 2014-10-09T12:49:31Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:16Z (GMT). No. of bitstreams: 1 10380.pdf: 7268074 bytes, checksum: fcb1abf468040268c71659acc3619d8d (MD5) / Tese (Doutoramento) / IPEN/T / Intituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP