Color center formation in alpha-Al2O3 induced by high energy heavy ions

Single crystals of alpha-alumina were irradiated at room temperature with 1.157 (GeVFe)-Fe-56, 1.755 (GeVXe)-Xe-136 and 2.636 (GeVU)-U-238 ions to fluences range from 8.7 x 10(9) to 6 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet visible absorption measurements. The investigation reveals the presence of various color centers (F, F+, F-2(2+), F-2(+) and F-2 centers) appearing in the irradiated samples. It is found that the ratio of peak absorbance of F-2 to F centers increases with the increase of the atomic numbers of the incident ions from Fe, Xe to U ions, so do the absorbance ratio of F-2(2+) to F+ centers and of large defect cluster to F centers, indicating that larger defect clusters are preferred to be produced under heavier ion irradiation. Largest color center production cross-section was found for the U ion irradiation. The number density of single anion vacancy scales better with the energy deposition through processes of nuclear stopping, indicating that the nuclear energy loss processes determines the production of F-type defects in heavy ion irradiated alpha-alumina.

Color center formation in silica glass induced by high energy Fe and Xe ions

Silica glass samples were implanted with 1.157 GeV Fe-56 and 1.755 GeV Xe-136 ions to fluences range from 1 x 10(11) to 3.8 x 10(12) ions/cm(2). Virgin and irradiated samples were investigated by ultraviolet (UV) absorption from 3 to 6.4 eV and photoluminescence (PL) spectroscopy. The UV absorption investigation reveals the presence of various color centers (E' center, non-bridging oxygen hole center (NBOHC) and ODC(II)) appearing in the irradiated samples. It is found that the concentration of all color centers increase with the increase of fluence and tend to saturation at high fluence. Furthermore the concentration of E' center and that of NBOHC is approximately equal and both scale better with the energy deposition through processes of electronic stopping, indicating that E' center and NBOHC are mainly produced simultaneously from the scission of strained Si-O-Si bond by electronic excitation effects in heavy ion irradiated silica glass. The PL measurement shows three emissions peaked at about 4.28 eV (alpha band), 3.2 eV (beta band) and 2.67 eV (gamma band) when excited at 5 eV. The intensities of alpha and gamma bands increase with the increase of fluence and tend to saturation at high fluence. The intensity of beta band is at its maximum in virgin silica glass and it is reduced on increasing the ions fluence. It is further confirmed that nuclear energy loss processes determine the production of alpha and gamma bands and electronic energy loss processes determine the bleaching of beta band in heavy ion irradiated silica glass. (c) 2009 Elsevier B.V. All rights reserved.

Energy systems and their impacts on marine ecosystem services

Global warming and its link to the burning of fossil fuels has prompted many governments around the world to set legally binding greenhouse gas reduction targets which are to be partially realised through a stronger reliance on renewable (e.g. wind) and other lower carbon (i.e. natural gas and nuclear) energy commodities. The marine environment will play a key role in hosting or supporting these new energy strategies. However, it is unclear how the construction, operation and eventual decommissioning of these energy systems, and their related infrastructure, will impact the marine environment, the ecosystem services (i.e. cultural, regulating, provisioning and supporting) and in turn the benefits it provides for human well-being. This uncertainty stems from a lack of research that has synthesised into a common currency the various effects of each energy sector on marine ecosystems and the benefits humans derive from it. To address this gap, the present study reviews existing ecosystem impact studies for offshore components of nuclear, offshore wind, offshore gas and offshore oil sectors and translates them into the common language of ecosystem service impacts that can be used to evaluate current policies. The results suggest that differences exist in the way in which energy systems impact ecosystem services, with the nuclear sector having a predominantly negative impact on cultural ecosystem services; oil and gas a predominately negative impact on cultural, provisioning, regulating and supporting ecosystem services; while wind has a mix of impacts on cultural, provisioning and supporting services and an absence of studies for regulating services. This study suggests that information is still missing with regard to the full impact of these energy sectors on specific types of benefits that humans derive from the marine environment and proposes possible areas of targeted research.

Energy storage in electrochemical capacitors: designing functional materials to improve device performance

Electrochemical capacitors, also known as supercapacitors, are becoming increasingly important components in energy storage, although their widespread use has not been attained due to a high cost/ performance ratio. Fundamental research is contributing to lowered costs through the engineering of new materials. Currently the most viable materials used in electrochemical capacitors are biomassderived and polymer-derived activated carbons, although other carbon materials are useful research tools. Metal oxides could result in a step change for electrochemical capacitor technology and is an exciting area of research. The selection of an appropriate electrolyte and electrode structure is fundamental in determining device performance. Although there are still many uncertainties in understanding the underlying mechanisms involved in electrochemical capacitors, genuine progress continues to be made. It is argued that a large, collaborative international research programme is necessary to fully develop the potential of electrochemical capacitors.

Critical energies for SSB and DSB induction in plasmid DNA by low-energy photons: action spectra for strand-break induction in plasmid DNA irradiated in vacuum

Purpose: To measure action spectra for the induction of single- strand breaks (SSB) and double-strand breaks (DSB) in plasmid DNA by low-energy photons and provide estimates for the energy dependence of strand-break formation important for track-structure simulations of DNA damage.

The energy factbook : a resource for South Carolina

This fact book describes An introduction to energy, energy basics, South Carolina’s energy situation, nuclear energy, electricity, solar energy, energy conservation and alternative fuels.

Reactores a tório: o futuro da energia nuclear de fissão

Dissertação para a obtenção do grau de mestre em Engenharia Electrotécnica Ramo de Energia

Best Available Techniques (BAT) and coal fired power stations: Can the energy gap be plugged without increasing emissions?

At present, there is much anxiety regarding the security of energy supplies; for example, the UK and other European States are set to become increasingly dependant upon imports of natural gas from states with which political relations are often strained. These uncertainties are felt acutely by the electricity generating sector, which is facing major challenges regarding the choice of fuel mix in the years ahead. Nuclear energy may provide an alternative; however, in the UK, progress in replacing the first generation reactors is exceedingly slow. A number of operators are looking to coal as a means of plugging the energy gap. However, in the light of ever more stringent legal controls on emissions, this step cannot be taken without the adoption of sophisticated pollution abatement technology. This article examines the role which legal concepts such as Best Available Techniques (BAT) must play in bringing about these changes.

What role for nuclear power in Japan after Fukushima?

This chapter brings a human security lens to bear on the energy-mix question in post-Fukushima Japan. In particular, two of the four elements of human security identified in the 1994 Human Development Report (HDR), prevention and people-centeredness, are mobilized. We trace developments in Japan’s post-Fukushima nuclear politics through the demise of DPJ rule to the advent of the LDP government, and evaluate the current nuclear energy strategy of the Abe administration. Using a human security framework, we consider the economic security dimension of the arguments for and against the use of nuclear power, and weigh the result of this consideration against a concern with the six other elements of human security identified in the 1994 HDR. We conclude that the risks and threats to human security engendered by the use of nuclear energy outweigh any benefits that could reasonably be argued to accrue from its use. The notion of prevention, so central to the concept of human security, performs a further ‘trumping’ function, in leading us to put a premium on the downside risk of the use of nuclear energy.

The decline of the world`s energy intensity

Energy intensity of the total primary energy supply (TPES), total final energy consumption (TFC) and LOSSES in the conversion from TPES to TFC were analyzed for the World, OECD and Rest of the World (ROW) countries. LOSSES increased significantly for all groups of countries due to the increase of electricity production from coal in the period studied (1971-2008). Electricity share final consumption almost doubled, increasing from 8.8% to 17.2% in the period studied. However the energy intensity of LOSSES remained practically constant, which reflects the fact that the efficiency of electricity generation from coal (the main source of electricity) remained practically constant in that period. Despite the attractiveness of end-use devices running on electricity such as computers, which is typical of modern societies, the CO(2) emissions are bound to increase unless coal is replaced by less carbon emitting sources such as natural gas, renewables and nuclear energy. (C) 2011 Elsevier Ltd. All rights reserved.

New mechanical samples positioning system for irradiations on a radial channel at nuclear research reactor in a full-power continuous operation

This paper describes a new mechanical samples positioning system that allows the safe placement and removal of biological samples for prolonged irradiation, in a nuclear reactor during full-power continuous operation. Also presented herein the materials of construction and operating principles. Additionally, this sample positioning system is compared with an existing pneumatic and automated transfer system, already available at the research reactors. The system consists of a mechanical arm with a claw, which can deliver the samples for irradiations without reactor shutdown. It was installed in the lEA-R1 research reactor at Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, Brazil, and for the past 5 years, the system has successfully operated and allowed the conducting of important experiments. As a result of its introduction, the facility has been in a position to positively respond to the increased demand in studies of biology, medicine, physics, engineering, detector/dosimeter calibrations, etc. It is one example of the appropriated technologies that save energy and resources. (C) 2010 Elsevier Ltd. All rights reserved.

Regulação estatal do setor nuclear: estudo comparativo dos modelos da Argentina e do Brasil

Este estudo apresenta uma análise comparativa dos modelos de regulação dos setores nucleares da Argentina - a cargo da Autoridad Regulatoria Nuclear (ARN), e do Brasil- sob a responsabilidade da Comissão Nacional de Energia Nuclear (CNEN), que procura identificar, por meio de critérios de análise selecionados a partir do referencial teórico, qual modelo é o mais adequado objetivando o uso seguro da energia nuclear. O Capítulo I apresenta uma breve descrição dos modelos de regulação dos setores nucleares do Brasil e da Argentina, bem como os objetivos, a delimitação do estudo e a relevância da pesquisa. O referencial teórico, Capítulo 2, contém tópicos sobre a reforma do Estado, os tipos de regulação, a regulação no Brasil e as características do setor nuclear internacional e brasileiro. A seguir, foram selecionados critérios de análise que correspondem às características das agências reguladoras brasileiras criadas para outros setores da economia, no bojo da reforma de Estado implementada no Brasil a partir de meados dos anos 90. Posteriormente, estes critérios de análise foram utilizados como parâmetros de comparação entre os modelos de regulação dos setores nucleares da Argentina e do Brasil. A metodologia de pesquisa é descrita no Capítulo 3, definindo-se o tipo de pesquisa, o universo e a amostra, a forma de coleta e tratamento dos dados e as limitações do método empregado. No Capítulo 4 é descrito o modelo de regulação do setor nuclear argentino, apresentando-se também um breve histórico sobre a criação da ARN. O Capítulo 5 apresenta a descrição do modelo de regulação do setor nuclear brasileiro, os estudos e recomendações existentes sobre a regulação do setor e os resultados da pesquisa empírica realizada junto aos servidores da CNEN. Com base na análise comparativa, Capítulo 6, pode-se concluir, Capítulo 7, que a estrutura regulatória e fiscalizadora do setor nuclear argentino, sob responsabilidade da ARN, mostra-se mais adequada no que tange ao uso seguro da energia nuclear, do que o modelo adotado no Brasil pela CNEN, pois incorpora os critérios de independência funcional, institucional e financeira, definição de competências, excelência técnica e transparência, necessários ao desempenho de suas funções de forma autônoma, ética, isenta e ágil.

Vitória na derrota: Álvaro Alberto e as origens da política nuclear brasileira

Os primeiros anos da política nuclear brasileira, entre os anos de 1945 e 1956, é o assunto tratado no presente trabalho. Aqui procuramos compreender as razões por trás da vitória de Álvaro Alberto na CPI da Questão Nuclear de 1956, na qual as suas propostas para o setor foram valorizadas e restabelecidas, mesmo após o Almirante ter sofrido derrotas durante o governo Café Filho (1954-55), quando foi exonerado da presidência do CNPq e teve a sua política atômica suspensa. O trabalho conclui que a vitória foi possível graças ao fato de as suas diretrizes para a área nuclear terem ressonância junto a diversos setores da sociedade brasileira adeptos do monopólio estatal sobre os recursos naturais e de um desenvolvimento científico e tecnológico em bases autônomas; além de uma conjuntura política excepcional no início do governo de Juscelino Kubitschek, marcado por forte polarização política, na qual o assunto nuclear ganhou projeção nacional. Com a sua vitória na CPI de 1956, Álvaro Alberto logrou definir os termos debate sobre a política a ser adotada na área atômica pelos anos e décadas seguintes.

O Programa Nuclear e a construção da democracia : análise da oposição ao Programa Nuclear Brasileiro (1975-1990)

O recorte analítico deste trabalho percorre os anos entre 1975 e 1990, fazendo uma análise sobre diferentes instâncias de oposição doméstica ao Programa Nuclear Brasileiro. A aludida oposição é entendida dentro do contexto político que o Brasil atravessava neste período, que coincide com a distensão do regime militar, a transição para governos civis e, depois, democraticamente eleitos. Nesse sentido, para além de construir uma narrativa sobre oposições domésticas ao programa nuclear e contribuir para as recentes interpretações historiográficas sobre a energia nuclear no Brasil, este trabalho busca situar estes atores dentro do contexto histórico do Brasil, avaliando seu impacto tanto na política nuclear quanto no contexto mais amplo da longa transição que encerrou o regime militar e trouxe o poder de volta para os civis.