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.

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.

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.

Made available in DSpace on 2014-06-11T19:31:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-23Bitstream added on 2014-06-13T21:02:19Z : No. of bitstreams: 1 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.

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.

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.

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.

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.

Made available in DSpace on 2014-06-11T19:23:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-28Bitstream added on 2014-06-13T19:50:58Z : No. of bitstreams: 1 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

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