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Estimation of iron-55 volumetric contamination via surrogates produced during Z-machine operationsFlores-McLaughlin, John 2008 August 1900 (has links)
Analysis of the radiation produced by Z-machine nuclear experiments at Sandia
National Laboratory and the materials irradiated indicate that the majority of produced
radionuclides can easily be detected. One significant exception is volumetric
contamination of stainless steel by iron-55. Detecting iron-55 in Z-machine components
presents a particular problem due to its low-abundance and the low-energy (5.9 keV) xray
it emits. The nuclide is often below the minimum detectable activity (MDA)
threshold and resolution criteria of many standard radiation detection devices. Liquid
scintillation has proven useful in determining iron-55 presence in loose contamination at
concentrations below that of regulatory guidelines, but determination of volumetric iron-
55 contamination remains a significant challenge. Due to this difficulty, an alternate
method of detection is needed. The use of radioactive surrogates correlating to iron-55
production is proposed in order to establish an estimate of iron-55 abundance.
The primary interaction pathways and interaction probabilities for all likely
radionuclide production in the Z-machine were tabulated and radionuclides with
production pathways matching those of iron-55 production were noted. For purposes of nuclide identification and adequate detection, abundant gamma emitters with half-lives
on the order of days were selected for use as surrogates.
Interaction probabilities were compared between that of iron-55 production and a
chosen surrogate. Weighting factors were developed to account for the differences in the
interaction probabilities over the range of the known energy spectra produced on the
device.
The selection process resulted in cobalt-55, cobalt-57 and chromium-51 as
optimal surrogates for iron-55 detection in both deuterium and non-deuterium loaded
interactions. A decay corrected correlation of the surrogates (chromium-51, cobalt-57 and
cobalt-55) to iron-55 for deuterium and non-deuterium loaded Z-machine driven
reactions was derived.
The weighting factors presented here are estimates which are based on rough
comparisons of cross-section graphs. Analysis considering factors such as energy
spectrum criteria to provide refined weighting factors may be utilized in future work.
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Padronização dos radionuclídeos sup(201)Ti e sup(55)Fe em sistema de consciências 4`pi`(PC)-Nal(Ti) / Standardization of 201Ti and 55Fe radionuclides in a 4(PC)-Nal(Ti) coincidence systemPIRES, CARLOS A. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:54:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:47Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP
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Padronização dos radionuclídeos sup(201)Ti e sup(55)Fe em sistema de consciências 4`pi`(PC)-Nal(Ti) / Standardization of 201Ti and 55Fe radionuclides in a 4(PC)-Nal(Ti) coincidence systemPIRES, CARLOS A. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:54:19Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:47Z (GMT). No. of bitstreams: 0 / No presente trabalho foi desenvolvido o método de padronização de radionuclídeos produzidos em cíclotrons utilizando o sistema de coincidências 4(PC)-NaI(Tl) composto de um contador proporcional operando a 0,1 MPa. Os radionuclídeos selecionados, foram o 201Tl, de uso em medicina nuclear e o 55Fe padrão primário muito utilizado na calibração de espectrômetros de raios-x. O 201Tl desintegra pelo processo de captura eletrônica, seguido pela emissão de radiação gama. A taxa de desintegração foi determinada pela técnica de extrapolação linear da eficiência empregando dois métodos: discriminação eletrônica e absorvedores externos. As fonte radioativas foram preparadas em substratos de Collodion com espessura de 20 g cm-2. O sistema eletrônico utilizado é o convencional para este tipo de medida. Os eventos observados foram registrados empregando o método TAC. O 55Fe desintegra pelo processo de captura eletrônica decaindo diretamente para o estado fundamental do 54Mn, emitindo raios-x com aproximadamente 6 keV. A taxa de desintegração foi determinada pelo método do traçador. Esta técnica foi aplicada utilizando dois radionuclídeos traçadores, que decaem pelo processo de captura eletrônica seguido da emissão de fótons, são eles 51Cr e 54Mn. As medidas foram feitas com 1 e 2 absorvedores de Al com espessura de 150 g cm-2. A atividade foi obtida extrapolando para zero espessura de Al. As incertezas envolvidas e suas correlações foram analisadas seguindo a metodologia de matriz de covariâncias. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN/CNEN-SP
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