The displacement damage induced by primary recoils of fusion neutrons in tungsten and alloys has been studied with self-ion irradiations, followed by damage characterization with electron microscopy. Tungsten and alloys (≤ 5 wt.% Re, Ta, V) were implanted with 2 MeV W+ ions over a dose range of 3.3×1017 - 2.5×1019 W+m-2 at temperatures ranging from 300 to 750°C. Dislocation loops of b = ½<111> (> 60%) and b = <100> were identified, and that ½<111> loops were found more thermally stable. Among loops that were large enough for nature determination, at least 50% were found to be of interstitial type, with larger fractions in high-temperature and high-dose conditions. The diameter of loops did not exceed 20 nm, with the majority being ≤ 5 nm. The loop number density varied between 1022 and 1023 m-3. The effects of ion dose, irradiation temperature, composition and grain orientation on damage microstructure were investigated. In-situ irradiations (150 keV W+ ions) were carried out as a complement to the bulk implantations. Qualitative trends in loop size, geometry and nature with irradiation dose and temperature were similar to bulk irradiated specimens. Also, the dynamics of defects and their effects on the damage evolution were explored. In-situ annealing of irradiated thin foils was performed to investigate the thermal stability of radiation damage in tungsten. The majority of microstructure transformations were completed within 15 min of annealing. However, extended durations did favour the increase of loop size and the fraction of ½<111> loops.

Nenhuma / Microanalysis performed in situ by electron microprobe technique (EPMA) enabled systematic and detailed studies of chemical dating of monazite from marine placers in Buena region, northern coast of Rio de Janeiro State. High spatial resolution BSE imaging allowed recognizing complex internal zoning and selecting spots for microanalysis. Zoning patterns commonly concentric and complex types for every heterogeneous grains studied presented remarkably similar composition. Heterogeneous patterns probably are associated with metamorphic recristalization (peak of metamorphism) and/or dissolution-reprecipitation (retrograde metamorphism) processes which transported Th contents between different domains of heterogeneous grains. Homogeneous grains are scarce and could be specific cross-cutting section of domains from heterogeneous grains. Following elements have been identifyied by EPMA: Ce, La, Pr, Nd, Sm, Gd, Dy, Y, Th, U, Pb, Si, Ca, Fe and Mn and revealed a typical Monazite-(Ce) composition. Th contents for concentric heterogeneous grains range from &#8776; 4 to 7 wt% and from &#8776; 2 to 10 wt% for complex heterogeneous grains are related to magmatic monazites undergone to metamorphic processes. Light rare earth elements (including Gd) demonstrate strong depletion related to Dy and Y in every analysed grain of monazite. (La/Nd)N ratio for both heterogeneous (&#8776; 1.5 a 2.7) and homogeneous grains (&#8776; 1.7 a 3.2) is similar, as well as (La/Y)N ratio shows an average value approximately ~ 200 for all grains. U-Th-Pb contents yielded chemical ages in the range since 592 to 530Ma consistent with metamorphism peak during 590 and 550Ma sin-collisional event of the Araçuaí/Ribeira Belt related to Mantiqueira Tectonic Province. Isotopic age data obtained by LA-ICP-MS (580 to 530Ma) are equivalent to chemical ages and validate the laborious methodology for U-Th-Pb ages by EPMA developed and applied in this study. Supported on ages and igneous and metamorphic growing patterns showed by heterogeneous grains, the suggested source rocks for monazite from Buena could possibly be related with lithologies of G2 and G3 suite, crystalized and submitted to metamorphic processes from high-amphibolite to granulite facies. / As microanálises executadas in situ pela microssonda eletrônica, segundo a metodologia desenvolvida neste trabalho, tornaram possível um estudo sistemático da química mineral e datação U-Th-Pb da monazita proveniente de pláceres marinhos na região de Buena-RJ, litoral norte fluminense. Imagens obtidas por elétrons retroespalhados com alta resolução espacial permitiram reconhecimento de complexo zoneamento interno e posicionamento dos pontos para execução das microanálises. Os padrões de zoneamento comumente encontrados em todos os grãos heterogêneos estudados correspondem aos tipos concêntricos e complexos que apresentam composições muito semelhantes. As heterogeneidades de grãos provavelmente estão associadas a processos de recristalização durante metamorfismo progressivo (pico do metamorfismo) e/ou dissolução-reprecipitação (retrometamorfismo), os quais remanejam os teores de Th entre os diferentes domínios dos grãos. Escassos grãos homogêneos de monazita parecem tratar de uma seção de corte em domínios específicos de grãos heterogêneos. Os seguintes elementos foram identificados por EPMA: Ce, La, Pr, Nd, Sm, Gd, Dy, Y, Th, U, Pb, Si, Ca, Fe e Mn e apontam para composição de monazita-(Ce). Os teores em Th para grãos heterogêneos concêntricos no intervalo entre &#8776; 4 e 7 % (peso) e para grãos heterogêneos complexos entre &#8776; 2 a 10 % (peso) são semelhantes aos valores de monazita magmática submetidas a processos metamórficos. A distribuição de elementos terras-raras em todos os grãos apresenta um forte empobrecimento dos elementos mais leves (incluindo Gd), em relação a Dy e Y. A razão (La/Nd) N para os grãos heterogêneos (&#8776; 1.5 a 2.7) e homogêneos (&#8776; 1.7 a 3.2) é equivalente. O valor médio em torno de 200 na razão (La/Y) N é similar nos grãos homogêneos e heterogêneos. A partir de teores de U-Th-Pb foram determinadas idades químicas no intervalo entre 530 e 592Ma relacionadas com o pico do metamorfismo regional da Província Mantiqueira, durante a fase sin-colisional da Faixa Araçuaí/Ribeira, onde idades variam entre 590 e 550Ma. Idades isotópicas realizadas por LA-ICP-MS forneceram idades (530 e 580Ma) compatíveis com as idades químicas. Esses resultados comprovam a validade da laboriosa rotina analítica para obtenção das idade U-Th-Pb em monazita, utilizando a microssonda eletrônica, que foi desenvolvida e aplicada durante este trabalho. Com base nas idades e nos padrões ígneos e metamórficos de desenvolvimento dos grãos heterogêneos, as prováveis rochas-fonte desses grãos de monazita seriam as litologias das suítes G2 e G3 que foram cristalizadas e, concomitantemente, submetidas a processos de metamorfismo que variaram de fácies anfibolito alto a granulito.

"Radionuclides in particulate matter associated with outdoor and indoor dusts were analyzed to determine the form and concentration of radioactive isotopes present. These radioactive isotopes, such as Strontium 90, Cesium 137, and Uranium 235, consist of, or are sorbed onto fine particulate matter, (PM). The airborne dispersion of this fine particulate matter results in the facilitated transport of these sorbed or neat radionuclides. Sources of particulate-bound radioactive contaminants include fallout from weapons testing, accumulation of radon daughters, transport of soils containing naturally-occurring radioactive material, remediation of radiologically-contaminated sites, and nuclear material processing. Radiological contaminants in PM, may exist as trace contamination in homogenous collections of particles, but may also exist heterogeneously, as a small number of high-concentration radionuclides among a larger set of uncontaminated particles. A total of 114 samples of indoor and outdoor airborne dusts were collected from a former nuclear weapons production facility near Richland, WA, the Los Alamos National Laboratory, and the Yakama Indian Nation in Wapato, WA. Los Alamos, NM was also the site of the May 2000 Cerro Grande wildfire. The wildfire created very large amounts of airborne particulate matter, including smoke and soot. The area affected by open burning included 43,000 acres. At the national laboratory, greater than 7600 acres were affected, including some areas that were radiologically- contaminated, such as a U-238 ammunition firing area. (LANL, 2007) This introduces a potential source of hot particles in dusts and other archived particulate matter, which may remain in the environment. LANL Airborne radionuclide surveillance has historically found higher uranium levels during windy periods, and saw elevated air uranium levels associated with the Cerro Grande fire. (Ibid, p. 108) Dust samples were sieved to pass a 150 micron screen and analyzed by gamma spectroscopy. Samples with higher activity were analyzed by Scanning Electron Microscopy/Energy Dispersive X-ray analysis, SEM/EDS. The results of gamma spectroscopy and individual particle counts were compared to determine the degree of radioactive heterogeneity in each sample. Radioactive heterogeneity, isotopic distribution, and particle size can be related to the source of the radioactive PM. Radiological contaminants in particulate matter, (PM), may exist as trace contamination in homogenous collections of particles, but may also exist heterogeneously, as a small number of high-concentration radionuclides among a larger set of uncontaminated particles. Residential and source area dusts were collected from locations surrounding, and potentially impacted, by operational and remedial activities at the HNR. The dust samples were analyzed, by multiple means, in order to identify those with radiologically- contaminated particles. Samples with higher activity were further analyzed by Scanning Electron Microscopy/Energy Dispersive X-ray analysis, (SEM/EDS), to determine if the radiological contamination was homogenous or heterogeneous. Two case studies were followed. The method isolated and analyzed lead and bismuth from naturally occurring radioactive material in coal fly ash. The method isolated and fingerprinted thorium, and the rare earths cerium, lanthanum, samarium, neodymium, and gadolinium in sedimentary cerium monazite minerals, nuclear waste processing dusts, and fission waste products in a WWTP effluent channel."

第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告

One of the main risks that exposed and unvegetated tailings pose to the environment and human health is airborne dust that may be inhaled or ingested. In the case of Pb-bearing dust, both particle size and the identity of the Pb-hosting minerals affect the degree of risk. Finer dusts (<5µm diameter) have a higher potential of being ingested deeper into the human lung causing possible tissue damage and toxic effects. We have collected size-fractionated airborne dust and near-surface pH-neutral tailings at New Calumet Mine, Quebec, Canada, a former Pb-Zn mine. Bioaccessibility describes how much of a substance can be dissolved by body fluids and become available for absorption by the body. The most bioaccessible Pb compounds are PbCO3 (cerussite), Pb3(CO3)2(OH)2 (hydrocerussite) and PbO, followed by PbSO4 (anglesite), PbS (galena) and Pb5(PO4)3Cl (pyromorphite). Airborne dust samples were collected on the tailings piles using a PIXE Cascade Impactor which separates aerosol fractions onto nine impactor stages ranging from 16µm to 0.06µm. These stages were then analyzed by PIXE to obtain elemental concentrations. Samples of non-vegetated and vegetated near-surface tailings were collected for bioaccessibility tests as well as for total metal content, grain size distribution, and Pb speciation using ESEM and synchrotron techniques. Both airborne dust and near-surface tailings samples underwent synchrotron microanalysis including microXRD for identification of microcrystalline compounds and microXRF for element mapping and metal ratio evaluation. Despite extensive oxidation of iron sulfide minerals in the near-surface tailings, galena persists as the most abundant Pb-bearing phase in the pH-neutral tailings. However, rims of cerussite and hydrocerussite forming alteration rims on galena grains have been identified throughout the tailings. In vitro bioaccessibility testing of Pb in the tailings resulted in 0-0.05% bioaccessible Pb in lung fluid and 23-69% bioaccessible Pb in the gastric fluid. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2012-02-28 21:09:08.432

No description available.

No description available.

Thesis (Ph. D.)--Pennsylvania State University. / Includes bibliographical references (p. 118-124).

Thesis (Ph. D.)--Lehigh University, 2005. / Includes vita. Includes bibliographical references (leaves 261-275).

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