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Analysis of tru-fueled vhtr prismatic core performance domainsLewis, Tom Goslee 15 May 2009 (has links)
The current waste management strategy for spent nuclear fuel (SNF) mandated by the
U.S. Congress is the disposal of high-level waste (HLW) in a geological repository at
Yucca Mountain. Ongoing efforts on closed-fuel cycle options and difficulties in
opening and safeguarding such a repository have led to investigations of alternative
waste management strategies. One potential strategy would make use of fuels containing
transuranic (TRU) nuclides in nuclear reactors. This would prolong reactor operation on
a single fuel loading and by doing so, would reduce current HLW stockpiles. The
analysis has already shown that high-temperature gas-cooled reactors (HTGRs) and their
Generation IV extensions, very-high-temperature reactors (VHTRs), have encouraging
performance characteristics that will allow for prolonged operation with no intermediate
refueling, as well as for transmutation of TRUs.
The objective of this research was to show that TRU-fueled VHTRs have the possibility
of prolonged operation on a single fuel loading while retaining their Generation IV safety
features. In addition, this research evaluated performance characteristics, and identified
operational domains of these systems, as well as the possibility of HLW reduction.
A whole-core, 3-D model of a power size prismatic VHTR with a detailed temperature
distribution was developed for calculations with the SCALE 5.1 code package. Results
of extensive criticality and depletion calculations with multiple fuel loadings showed that
VHTRs are capable and suitable for autonomous operation when loaded with TRU fuel.
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Impact of PWR spent fuel variations on TRU-fueled VHTRSAlajo, Ayodeji Babatunde 15 May 2009 (has links)
Several alternative strategies are being considered as spent nuclear fuel (SNF) management options. Transuranic nuclides (TRU) are responsible for the SNF long-term radiotoxicity beyond the first 500 years. One of the most viable approaches suggests creating new transmutation fuels containing TRUs for use in thermal and fast nuclear reactors. Irradiation of TRUs results in their transmutation and ultimate incineration by fission. The objective of this thesis is to analyze the impact of conventional PWR spent fuel variations on TRU-fueled Very High Temperature Reactor (VHTR) systems. This effort was focused on the prismatic core configuration. The 3D core models were created for use in calculations with the SCALE 5.1 code system. As part of the research effort, basic nuclear characteristics of TRUs were taken into consideration. The potential variations of PWR spent fuel compositions were modeled with the International Atomic Energy Agency (IAEA) Nuclear Fuel Cycle Simulation System, VISTA. The VHTR configurations with varying TRU compositions were analyzed assuming a single-batch core operation. Their performance was compared to the VHTR cases with low enriched uranium (LEU). The analysis shows that TRUs can be effectively utilized in the VHTR systems. The TRU-fueled VHTRs exhibit favorable performance characteristics.
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Impact of PWR spent fuel variations on TRU-fueled VHTRSAlajo, Ayodeji Babatunde 15 May 2009 (has links)
Several alternative strategies are being considered as spent nuclear fuel (SNF) management options. Transuranic nuclides (TRU) are responsible for the SNF long-term radiotoxicity beyond the first 500 years. One of the most viable approaches suggests creating new transmutation fuels containing TRUs for use in thermal and fast nuclear reactors. Irradiation of TRUs results in their transmutation and ultimate incineration by fission. The objective of this thesis is to analyze the impact of conventional PWR spent fuel variations on TRU-fueled Very High Temperature Reactor (VHTR) systems. This effort was focused on the prismatic core configuration. The 3D core models were created for use in calculations with the SCALE 5.1 code system. As part of the research effort, basic nuclear characteristics of TRUs were taken into consideration. The potential variations of PWR spent fuel compositions were modeled with the International Atomic Energy Agency (IAEA) Nuclear Fuel Cycle Simulation System, VISTA. The VHTR configurations with varying TRU compositions were analyzed assuming a single-batch core operation. Their performance was compared to the VHTR cases with low enriched uranium (LEU). The analysis shows that TRUs can be effectively utilized in the VHTR systems. The TRU-fueled VHTRs exhibit favorable performance characteristics.
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Estudo da viabilidade do uso da punção biópsia aspirativa por agulhas fina comparada ao da “tru-cut”, em testículo de cãesCunha, Guilherme Nascimento [UNESP] 23 July 2009 (has links) (PDF)
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cunha_gn_dr_jabo.pdf: 465416 bytes, checksum: e2fa65c0170bcd5725dafe063644725b (MD5) / O objetivo deste estudo foi avaliar histologicamente as biópsias testiculares de cães obtidas por punção aspirativa por agulhas fina (PAAF) e “tru cut”. Foram utilizados 40 cães, adultos, hígidos, distribuídos em 2 grupos: G1 - punção biópsia aspirativa; e G2 - biópsia com agulha “tru-cut”. Cada grupo foi dividido em quatro subgrupos (Ga, Gb, Gc e Gd) com cinco animais cada, sendo estes orquiectomizados 3, 7, 14 e 62 dias após as biópsias PAAF ou “Tru-cut”. O material colhido pela PAAF foi submetido à avaliação citológica, e o proveniente da biópsia “tru-cut” e orquiectomia submetidos à histopatologia. Foram avaliados os espermiogramas e mensuração de comprimento e largura do escroto e colhido o soro para pesquisa de anticorpo antiespermatozóides. Referente ao espermiograma e a mensuração do escroto não foram observados diferenças (p>0,05) significativas. A amostra direcionada para citologia e histologia obtida pelas duas técnicas foi considerada de quantidade suficiente para diagnóstico. Na histopatologia a PAAF apresentou menor área de lesão e reação inflamatória comparada a “tru cut”, no entanto esta última apresentou maior quantidade de material, preservando a arquitetura dos túbulos seminíferos e interstício. Não foi observado diferença (p>0,05) na produção de anticorpos anti-espermatozóides, após as biopsias. Concluímos que apesar das biópsias fornecerem material em qualidade e quantidade adequadas, e da PAAF ter se mostrado menos traumática, a escolha da técnica a ser empregada dependerá da finalidade para o qual o material se destina. / The aim of this study it was evaluate hystologicaly the testicular biopsies in dogs obtained by aspirative puncture by fine needle and “tru-cut”. Forty males dogs, adults, healthies were used, distributed in 2 groups: G1 – Fine Needle aspiration; and G2- biopsy by “Tru-cut”. Each group were shared in four groups (Ga, Gb, Gc e Gd) with 5 animals each, and all of then were orchiectomized after 3, 7, 14, 62 days after the biopsies by FNA and “tru-cut” being performed. The samples collected by FNA were submitted to cytology evaluate, and the sample from tru-cut biopsy and orchiectomy submitted to histopathology. The spermiograms were evaluated, the testicular length and with were measure, and the animal’s blood were collected to the anti-sperm antibody quantification. About the spermogram and measurement of scrotal bag any significative difference was observed (p>0,05). The sample to cytology and histology obtained from two techniques showed be in quantity enough to diagnostic. In histopathology, the biopsy FNA showed smaller damage area and inflammatory reaction compared to tru-cut, however this one showed biggest quantity of material, preserving the seminiferous tubules architeture and interstitium. It was not observed significative difference at anti-sperm antibodies production. We concluded that althought the biopsies provide material in quantity and quality appropriate, and the PAAF showed less traumatic, the choose of the technique to be used will depend the purpose for which the material is intended.
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High-Fidelity Nuclear Energy System Optimization towards an Environmentally Benign, Sustainable, and Secure Energy SourceAmes, David E. 2010 August 1900 (has links)
A new high-fidelity integrated system method and analysis approach was
developed and implemented for consistent and comprehensive evaluations of advanced
fuel cycles leading to minimized Transuranic (TRU) inventories. The method has been
implemented in a developed code system integrating capabilities of MCNPX for highfidelity
fuel cycle component simulations.
The impact associated with energy generation and utilization is immeasurable due
to the immense, widespread, and myriad effects it has on the world and its inhabitants.
The polar extremes are demonstrated on the one hand, by the high quality of life enjoyed
by individuals with access to abundant reliable energy sources, and on the other hand by
the global-scale environmental degradation attributed to the affects of energy production
and use. Thus, nations strive to increase their energy generation, but are faced with the
challenge of doing so with a minimal impact on the environment and in a manner that is
self-reliant. Consequently, a revival of interest in nuclear energy has followed with much
focus placed on technologies for transmuting nuclear spent fuel.
In this dissertation, a Nuclear Energy System (NES) configuration was developed
to take advantage of used fuel recycling and transmutation capabilities in waste
management scenarios leading to minimized TRU waste inventories, long-term activities,
and radiotoxicities. The reactor systems and fuel cycle components that make up the
NES were selected for their ability to perform in tandem to produce clean, safe, and
dependable energy in an environmentally conscious manner. The reactor systems include
the AP1000, VHTR, and HEST. The diversity in performance and spectral
characteristics for each was used to enhance TRU waste elimination while efficiently
utilizing uranium resources and providing an abundant energy source.
The High Level Waste (HLW) stream produced by typical nuclear systems was
characterized according to the radionuclides that are key contributors to long-term waste
management issues. The TRU component of the waste stream becomes the main
radiological concern for time periods greater than 300 years. A TRU isotopic assessment
was developed and implemented to produce a priority ranking system for the TRU
nuclides as related to long-term waste management and their expected characteristics
under irradiation in the different reactor systems of the NES.
Detailed 3D whole-core models were developed for analysis of the individual
reactor systems of the NES. As an inherent part of the process, the models were
validated and verified by performing experiment-to-code and/or code-to-code
benchmarking procedures, which provided substantiation for obtained data and results.
Reactor core physics and material depletion calculations were performed and analyzed.
A computational modeling approach was developed for integrating the individual
models of the NES. A general approach was utilized allowing for the Integrated System
Model (ISM) to be modified in order to provide simulation for other systems with similar
attributes. By utilizing this approach, the ISM is capable of performing system
evaluations under many different design parameter options. Additionally, the predictive
capabilities of the ISM and its computational time efficiency allow for system
sensitivity/uncertainty analysis and the implementation of optimization techniques.
The NES has demonstrated great potential for providing safe, clean, and secure
energy and doing so with foreseen advantages over the LEU once-through fuel cycle
option. The main advantages exist due to better utilization of natural resources by
recycling the used nuclear fuel, and by reducing the final amount and time span for which
the resulting HLW must be isolated from the public and the environment due to
radiological hazard. If deployed, the NES can substantially reduce the long-term
radiological hazard posed by current HLW, extend uranium resources, and approach the
characteristics of an environmentally benign energy system.
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Advanced Fuel Cycle Scenarios with AP1000 PWRs and VHTRs and Fission Spectrum UncertaintiesCuvelier, Marie-Hermine 2012 May 1900 (has links)
Minimization of HLW inventories and U consumption are key elements guaranteeing nuclear energy expansion. The integration of complex nuclear systems into a viable cycle yet constitutes a challenging multi-parametric optimization problem. The reactors and fuel cycle performance parameters may be strongly dependent on minor variations in the system's input data. Proven discrepancies in nuclear data evaluations could affect the validity of the system optimization metrics.
This study first analyzes various advanced AP1000-VHTR fuel cycle scenarios by assessing their TRU destruction and their U consumption minimization capabilities, and by computing reactor performance parameters such as the time evolution of the effective multiplication factor keff, the reactors' energy spectrum or the isotopic composition/activity at EOL. The performance metrics dependence to prompt neutron fission spectrum discrepancies is then quantified to assess the viability of one strategy. Fission spectrum evaluations are indeed intensively used in reactors' calculations. Discrepancies higher than 10% have been computed among nuclear data libraries for energies above 8MeV for 235U.
TRU arising from a 3wt% 235U-enriched UO2-fueled AP1000 were incinerated in a VHTR. Fuels consisting of 20%, 40% and 100% of TRU completed by UO2 were examined. MCNPX results indicate that up to 88.9% of the TRU initially present in a VHTR fueled with 20% of TRU and 80% of ThO2 were transmuted. Additionally, the use of WgPu instead of RgPu should reduce the daily consumption of 235U by 1.3 and augment core lifetime.
To estimate the system metrics dependence to fission spectrum discrepancies and validate optimization studies outputs, the VTHR 235U fission spectrum distribution was altered successively in three manners. keff is at worst lowered by 1.7% of the reference value and the energy spectrum by 5% between 50meV and 2MeV when a significantly distorted fission spectrum tail is used. 233U, 236Pu and 237Pu inventories and activities are multiplied by 263, 523 and 34 but are still negligible compared to 239Pu mass or the total activity.
The AP1000-VHTR system is in conclusion not dependent on the selected fission spectrum variations. TRU elimination optimization studies in AP1000-VHTR systems will be facilitated by freeing performance metrics dependency from 1 input parameter.
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The current water quality situation at clinics in the Limpopo Province and subsequent management suggestions / Jan Hendrik StanderStander, Jan Hendrik January 2010 (has links)
South Africa's water resources are, in global terms, scarce and extremely limited (DWAF, 2004).
Groundwater is a valuable source of potable water in South Africa. It was found that most of the health
facilities in the Limpopo Province depend on groundwater as sole source of potable water.
Groundwater quality is to a great extent influenced by the dominant land use in the vicinity of an
aquifer. It is therefore important to carefully manage possible pollution sources of anthropogenic origin.
This may be seen as pro–active water quality management that may result in significant saving on water
treatment.
This aim of this study is to obtain a regional view of the water quality situation at clinics and other health
facilities in the Limpopo Province. It was found that the general water quality at health facilities in the
Province is questionable. It is of concern to note that 56% of health facilities use water that is
unacceptable for human consumption.
Water quality may be managed by introducing appropriate treatment options to treat the water to ideal
water quality standards. This dissertation explores some treatment options used at health facilities in
the Province. The efficiency of these treatment systems is also investigated. / Thesis (M.Sc. (Geography and Environmental Studies))--North-West University, Potchefstroom Campus, 2011.
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The current water quality situation at clinics in the Limpopo Province and subsequent management suggestions / Jan Hendrik StanderStander, Jan Hendrik January 2010 (has links)
South Africa's water resources are, in global terms, scarce and extremely limited (DWAF, 2004).
Groundwater is a valuable source of potable water in South Africa. It was found that most of the health
facilities in the Limpopo Province depend on groundwater as sole source of potable water.
Groundwater quality is to a great extent influenced by the dominant land use in the vicinity of an
aquifer. It is therefore important to carefully manage possible pollution sources of anthropogenic origin.
This may be seen as pro–active water quality management that may result in significant saving on water
treatment.
This aim of this study is to obtain a regional view of the water quality situation at clinics and other health
facilities in the Limpopo Province. It was found that the general water quality at health facilities in the
Province is questionable. It is of concern to note that 56% of health facilities use water that is
unacceptable for human consumption.
Water quality may be managed by introducing appropriate treatment options to treat the water to ideal
water quality standards. This dissertation explores some treatment options used at health facilities in
the Province. The efficiency of these treatment systems is also investigated. / Thesis (M.Sc. (Geography and Environmental Studies))--North-West University, Potchefstroom Campus, 2011.
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Intoxicação experimental de cães com sementes de Crotalaria spectabilis (Leg. Papilionoideae)Bellodi, Carolina [UNESP] 28 July 2010 (has links) (PDF)
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bellodi_c_me_jabo.pdf: 837117 bytes, checksum: 80f9b7c3e6c45c6babff0aff0303c9c5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Sabe-se que a C. spectabilis é muito utilizada como adubação verde e para controle de nematóides, com isso espalha-se facilmente, misturando-se com o milho e outros cereais contaminando as rações. O objetivo do presente estudo foi o de avaliar os efeitos tóxicos da semente de Crotalaria spectabilis, quando trituradas e misturadas à ração de cães. Nesse experimento foram utilizados 12 cães, 6 machos e 6 fêmeas, com idades variadas, divididos em três grupos de 4 animais. Os tratamentos foram divididos por grupos, sendo que cada grupo recebeu respectivamente, 0,2, 0,4 e 0,6% de sementes de C. spectabilis, por 28 dias, que foram trituradas e adicionadas à ração. Semanalmente avaliou-se o perfil hematológico e bioquímico dos cães, além do exame físico realizado diariamente. Nos exames bioquímicos realizados, houve alteração significativa da enzima GGT. Os sinais clínicos observados foram, principalmente, alopecia periocular e alopecia difusa, além de hiperceratose nasal, espirros, tosse, vômitos esporádicos, constipação e fezes ressequidas. Para o exame histopatológico foi extraído um fragmento de fígado através de agulha tipo TRU-CUT®. Observou-se hepatócitos tumefados, vacuolização de células nos sinusóides, necrose focal, anisocitose, cariomegalia, células de Kupffer com variadas pigmentações, fibrose e presença de pigmento biliar nos hepatócitos caracterizando doença hepática. Concluise baseado nos exames histopatológicos que as concentrações oferecidas de sementes de C. spectabilis 0,2, 0,4 e 0,6% no período de 28 dias são tóxicas aos cães / It is known that C. spectabilis is widely used as green manure and for controlling nematodes, with that spreads easily, mingling with the infecting maize and other cereal rations. The aim of this study was to evaluate the toxic effects of Crotalaria spectabilis seeds, when crushed and mixed with the food of dogs. In this experiment we used 12 dogs, six males and six females, of various ages, which were divided into three groups of four animals. Each group received respectively 0.2, 0.4 and 0.6% of seeds of C. spectabilis, for 28 days, which were crushed and added to the diet. Weekly it was evaluated the hematological and biochemical profile of dogs, in addition to physical examination performed daily. In biochemical tests performed, significant alteration of the enzyme GGT. Clinical signs observed were mainly periocular alopecia and diffuse alopecia, and hyperkeratosis on nose, sneezing, coughing, occasional vomiting, constipation and dry feces. For the histopathology was extracted through a liver biopsy needle type TRU-CUT®, it was observed tumefactive hepatocytes, vacuolization of cells in the sinusoids, focal necrosis, anisocytosis cariomegalia, Kupffer cells with different pigmentation, fibrosis and presence of bile pigment in hepatocytes, characterizing liver disease. It was based on histopathological examinations offered that concentrations of seeds of C. spectabilis 0.2, 0.4 and 0.6% during the 28 days are toxic to dogs
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Opportunities for the development of understanding in Grade 8 mathematics classroomsde Jager, Gerdi January 2016 (has links)
Learner performance in South Africa is poor in comparison with other countries as
a result of poor teaching. At the core of the concern about learners' performance in
mathematics in South Africa lies a controversy regarding how mathematics should
be taught. The purpose of this study was to explore Grade 8 mathematics teachers'
creation and utilisation of opportunities for learners to develop mathematical
understanding in their classrooms. To accomplish this, an explorative case study
was conducted to explore three mathematics teachers' instructional practices by
using Schoenfeld et al.'s (2014) five dimensions of Teaching for the Robust
Understanding of Mathematics (TRU Math) scheme, namely, the mathematics,
cognitive demand, access to mathematical content, mathematical agency, authority
and identity and uses of assessment. The three participants were conveniently
selected from three private schools in Mpumalanga. The data collected consist of a
document analysis, two lessons observations and a post-observation interview per
teacher.
This study revealed that only one of the three teachers applied all Schoenfeld et
al.'s (2014) TRU Math dimensions. The dimension identified which the teachers
applied most in their classrooms was the mathematics. The dimensions identified
where teachers still lack skills were cognitive demand, access to mathematical
content, agency, authority and identity, and uses of assessment. This study
revealed that the content of most tasks and lessons was focused and coherent, and
built meaningful connections. However, the content did not engage learners in
important mathematical content or provided opportunities for learners to apply the
content to solve real-life problems. Due to the small sample used, the results from
this study cannot be generalised. However, I hope that the findings will contribute
to student-teacher training and in-service teacher training in both government and
private schools. Future research could possibly build on this study by examining
the learners and how they learn with understanding by using the TRU Math
dimensions. / Dissertation (MEd)--University of Pretoria, 2016. / Science, Mathematics and Technology Education / MEd / Unrestricted
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