D.Phil. / The existence of radioactive waste (or ‘radwaste’) has become a problem that afflicts the nuclear industry worldwide. The search for a social consensus on radwaste management strategies is proving to be one of the most complex challenges facing nuclear technological development. The categories of radwastes that are currently of greatest concern are spent nuclear fuel (SF) that is discharged from nuclear power reactors and high level waste (HLW) arising from reprocessing of SF, as they continue to accumulate in storage facilities around the world and perceived to be without an end solution to their existence. Like many other nuclear countries, South Africa too is facing major decisions about future management of SF that is generated from its nuclear power and research reactors. It remains undecided on which of the available spent fuel management (SFM) options it must adopt. This research study seeks to produce a framework for evaluating SFM options that will identify and characterise the elements or aspects to be analysed, and use it to evaluate the SFM options in order to identify a preferred or optimum option for South Africa. The methodological approach to this study involves the use of literature research, a case study on Eskom’s SFM approach and a questionnairebased survey complemented by in-depth interviews with key stakeholders of nuclear power in South Africa. These qualitative methods are used to verify and validate the SFM evaluation framework. To complement the qualitative approach, a cost analysis of the options based on input from Eskom and literature data as well as on assumed scenarios, is carried out. Both the qualitative and the cost analysis lead to identification of a preferred SFM option for South Africa. Three principal SFM options were identified and evaluated: the reprocessing and recycling (or closed fuel cycle) option, the direct disposal (or once-through fuel cycle) option, and the indefinite storage (or deferral-of-a-decision) option. There are at least nine categories of issues that have been identified as factors affecting these SFM options: technology, safety, environmental impact, proliferation resistance, physical security, economics, sociopolitical influence, ethical principles and institutional capability. These formed the evaluation framework and were used as the criteria for the assessment of the SFM options. Based on the analysis conducted in the study concerning the feasibility of the SFM options for the South African context in terms of these criteria, it is concluded that the direct disposal option is the most favourable option for implementation in the South African nuclear power programme. However, all three options have their technical merits but are also contentious in various degrees both within the nuclear industry and the public domain.

The selection of the form of spent nuclear fuel disposition, currently under debate, will precipitate an immediate requirement for spent-fuel transport regardless of the disposition alternative chosen. In this study, a constrained transportation model of the spent fuel cask scheduling problem is formulated with the objective of determining the minimum number of casks required to meet a fixed transport schedule. An iterative search procedure is employed to determine schedules which minimize cask idle time for each required spent fuel cask. The formulated model and the iterative search procedure are applied to a reference case to demonstrate their utility. An economic analysis of the results was performed to compare the truck and rail transport modes. Results indicate a substantial savings when rail transport is employed. An economic comparison of the cask lease and cask purchase options indicates that cask purchase is preferable for the 23-year planning horizon. / Master of Science

The purpose of this study is to determine the constituents of value in spent nuclear fuel and integrate these results into an economic time dependent model of a spent fuel assembly. The value of the constituents in the spent fuel is balanced against the cost of the various nuclear fuel cycle services. BWR and PWR-UO₂/MOX spent fuel assemblies are modeled at 5 different burnups. The recycle modes that are examined are uranium recycle with and without fission product sales and uranium and plutonium recycle with and without fission product sales. UO₂ and MOX spent fuel assemblies discharged from a nuclear reactor from 1977 to 1990 are modeled for a period of 19 years. Four key results of this study are: (1) a re-examination of the value of recycling materials other than uranium and plutonium, namely cesium-137, 134, rhodium, palladium and xenon is justified; (2) the magnitude of the net profits obtainable from the recycling of spent nuclear fuel are tied primarily to burnup and the decision to sell fission products; (3) for fission product recycle, any burnup yields a net positive value with the greater values being at high burnups; and (4) under only spent uranium and plutonium recycle, it is marginally profitable or unprofitable to recycle spent nuclear fuel. The utilization of cesium-137, 134 in the treatment of municipal sludge can reduce the importation of oil by 47.92 million U.S. barrels annually for the United States. / Master of Science

Brewer's spent grain (BSG) is the most abundant by-product of the brewing industry and its main application is limited to low-value cattle feed. Since BSG contains 20 to 25% of proteins, it has the potential to provide a new protein source to the food industry. In this research, an ultrasound-assisted enzymatic extraction was designed to extract protein hydrolysates from BSG. Original BSG and ultrasound pretreated BSG were hydrolyzed under different enzyme (Alcalase) loadings and incubation times. Centrifugation was applied to separate solubilized proteins from insoluble BSG residue. When the enzyme loading increased from 1 to 40 uL /g BSG, the solubilized proteins increased from 34% to 64.8%. The application of ultrasound further increased the solubilized proteins from 64.8% to 69.8%. Solubilized proteins from ultrasound pretreated BSG was significantly higher (p < 0.05) than that from the original BSG. Particle size distribution analysis showed that the application of ultrasound pretreatment reduced the BSG particle size from 331.2 to 215.7 um. Scanning electron microscopy images revealed that the BSG particle surface was partially ruptured by the ultrasound pretreatment. These two phenomena might have contributed to the increased protein separation efficiency with ultrasound pretreatment. The solubility (pH 1.0 to 11.0) of protein hydrolysate increased by the application of ultrasound and the ultrasound did not lead to the change of the amino acid composition of the separated protein hydrolysates. Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile, the protein was degraded to peptides which had molecular weights lower than 15 kDa. The color of the separated protein hydrolysates by enzymatic hydrolysis was brighter and lighter than the original BSG. The application of ultrasound did not affect the color of the separated protein hydrolysates. Overall, the ultrasound pretreatment prior to enzymatic hydrolysis enhanced the extraction of proteins from BSG in terms of higher protein separation efficiency, lower enzyme loadings, and reduced incubation time. This study developed a novel and green method to effectively extract value-added protein hydrolysates from the low-value food processing byproducts. / MSLFS / Brewer’s spent grain (BSG) is the most abundant waste generated by beer industries after beer production and it is mainly used to feed cattle. Since BSG contains 20 to 25% proteins, it has the potential to provide a new protein source to food industries. The aim of this research is to study if the ultrasound technology can assist the enzymatic extraction of proteins from BSG. If it can, the cost of the protein extraction from BSG can be reduced. In this research, the original BSG and the BSG pretreated with ultrasound were incubated under different enzyme loadings and incubation times. The protein-rich liquid was separated from fiber-rich solids using a centrifuge. When the enzyme loading increased from 1 to 40 L /g BSG, 34% to 64.8% of proteins were separated from the original BSG. The application of ultrasound further increased the solubilized proteins from 64.8% to 69.8%. For the BSG pretreated with ultrasound, there were significantly more proteins separated from BSG compared to the original BSG. Particle size of the original BSG and the ultrasound pretreated BSG was measured, and the results showed that the application of ultrasound pretreatment decreased the BSG particle size from 331.2 to 215.7 µm. Scanning electron microscopy images were taken to investigate the effect of ultrasound on the surface of BSG particles. Based on the photos, we found that the BSG particle surface was partially broken by the ultrasound pretreatment. The surface was rough and contained large amounts of holes instead of being flat and smooth observed without ultrasound. Therefore, there were more locations for the enzyme to attack. These two phenomena might have contributed to extracting more proteins from BSG. Protein solubility (pH 1.0 to 11.0) increased by the application of ultrasound. The nutritional value of the protein extracted was not altered by the ultrasound. The extracted protein hydrolysates had a small molecular weight and the application of ultrasound did not affect the color of the extracted protein hydrolysates. The ultrasound pretreatment prior to enzymatic hydrolysis increased the extraction of proteins from BSG, decreased the enzyme consumption and incubation time. This study developed a novel and green method to effectively extract value-added protein hydrolysates from the low-value food processing byproducts.

Spent nuclear fuel (SNF) resultant from the generation of nuclear power is a chemically and radiologically diverse system which is advantageous to chemically process prior to geologic disposal. Hydrometallurgy is the primary technology for chemical processing for light water reactor spent fuels, where spent fuel is dissolved in an acid for liquid based separations. The primary means for recovery of desired metals from the SNF solution is liquid-liquid extraction which is based on distribution (partitioning) of the metal ions between two immiscible phases based on thermodynamic favorability. One of the means of increasing this favorability is by designing extractant molecules to be either "harder" or "softer" bases, which will more preferentially extract harder or softer metal ions respectively. This technique is used in designing extractant molecules for targeted extraction as actinides are slightly softer than lanthanides, and precious metals produced in significant quantities from the fission process are especially soft metals. The work performed in this thesis involved the synthesis of a novel soft electron donor organic extractant molecule for testing of targeted soft metal extraction. The molecule synthesized was bis-dibutanethiolthiophosphinato-methane, or S6, a bidentate neutral extractant molecule with significant thiolysis for a softer electron environment. The synthesis technique was refined and the molecule composition and structure was confirmed by ¹H NMR, ³¹P NMR, and elemental analysis. Two metal groups, f-elements (actinides and lanthanides) and soft transition metals were tested for their extractability from nitric acid solutions into an S6 solution in n-dodecane. Aqueous solutions of nitric acid and n-dodecane as an organic diluent are typical liquid-liquid extraction conditions in spent nuclear fuel reprocessing. As extraction experiments were performed with radiotracers, for the soft metal extraction experiment, a mixture of the selected metals was neutron-activated in the OSU TRIGA reactor, as was europium to create a lanthanide radiotracer. Actinides and lanthanides were not seen to effectively extract into the organic or form a precipitate at all, making their partitioning with this extractant seemingly ineffective. Through gamma spectroscopy of an irradiated metal solution post-extraction, it is seen that only silver and palladium preferentially complex in the mixed metal samples into an insoluble organic ligand, dropping out of solution. This effect was more pronounced at higher acid concentrations, but silver was seen to slightly extract to the organic phase at all acid concentrations as well. This testing has shown that the S6 extractant can be used to recover silver and palladium from a mixed metal aqueous solution, such as one resultant from advanced spent nuclear fuel reprocessing operations. This result shows promise for future development of sulfur based organophosphate ligands for targeted extraction of precious metals from solutions. / Graduation date: 2013

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: van Rooijen, Wilfred; Committee Member: Hertel, Nolan; Committee Member: Stacey, Weston

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Aquaculture, the cultivation of aquatic organisms in a controlled environment, offers both economic and nutritional benefits to human society. As there is an increased demand to feed a growing human population, many wild-caught fisheries have struggled due to the overexploitation of resources. Currently, production relies heavily on wild-caught fish to produce fishmeal to feed farm-raised fish. The demand for alternative materials in fish feeds has grown rapidly as fishmeal resources have become limited. Antibiotic resistance emergence in aquaculture systems is another area of concern. Reducing antibiotic use via alternate prophylactic measures to increase host health is an essential area of research; modulation of the host intestinal bacterial community via prebiotics is one possibility. Prebiotics refer to non-digestible food ingredients that are thought to stimulate the growth of beneficial bacteria, consequently benefiting host health by indirectly reducing the possibility of bacterial pathogen proliferation. This occurs through various measures such as competition for space and resources. The intestinal bacterial community has a significant impact on a variety of host factors that include host development, physiology, immunity, and nutrient acquisition. In turn, there are multiple factors impacting the bacterial community, including the presence of pathogens and/or antibiotics, environmental conditions, host genetics, and the diet consumed. To promote environmental sustainability and improve production and animal health in aquaculture, a collaboration was created with Anheuser-Busch of the brewing industry and Maltento, a functional ingredient company. With breweries around the globe, Anheuser-Busch produces consistent, food grade byproducts that are safe for human consumption. Two of the most prevalent brewery byproducts are brewer's spent yeast (BSY) and brewer's spent grain (BSG). BSY contains a variety of beneficial nutrients such as proteins, essential amino acids, and carbohydrates. BSG is high in fiber but low in protein; however, black soldier fly larvae can be cultured on BSG to convert the low-value product into insect biomass to be used in fish feed, as insects themselves are full of beneficial lipids and proteins. The objective of the work presented in this thesis was to evaluate the efficacy of using low-value brewery waste products, converted into high-value feed additives, for aquaculture practices. Specifically, the effects of dietary feed additives on the production, health, and intestinal bacterial community of aquaculture-raised rainbow trout were examined. Inadvertently, benefits of the feed additives on fish subjected to chronic and acute thermal stress were also assessed. Overall, the results of the study found that the feed additives did not significantly change the production efficiency of the rainbow trout, though some increase in growth was observed. When subjected to chronic thermal stress conditions, fish fed the experimental diets outperformed those fed the control diet regarding growth parameters. The intestinal bacterial community of the fish was significantly altered from the beginning of the trial compared to the end of the trial, though differences were not attributed to the feed additives. Instead, the resulting intestinal dysbiosis is believed to have stemmed from the physiological response of the fish to thermal stress conditions. When the fish underwent an acute thermal stress event, causing mortality, fish fed three of the five experimental diets were found to have higher survival rates compared to the control. Ultimately, results of this project suggest that the BSY and BSG-fed insect feed additives may have increased the health and robustness of the fish during a period of thermal stress. However, further research under controlled conditions is needed to evaluate if the observed host health benefits can directly be attributed to the feed additives. / Master of Science / Aquaculture refers to the method of rearing aquatic organism such as fish and shellfish under controlled conditions. Within the food industry, aquaculture is one of the fastest growing sectors, and provides important economic and nutritional benefits to humans. Additionally, aquaculture is an important alternative to fisheries that rely on catching fish from the natural environment. Wild-caught fisheries have struggled due to the overfishing, and unfortunately, many aquaculture practices still rely on wild-caught fisheries to produce fishmeal used in feed for carnivorous fish. Research into alternate protein sources to use in fish feed has been on the rise. Additionally, as the emergence of multi-drug resistant bacteria continues to increase, reducing antibiotic use has become a priority across all fields whether it be healthcare or the food industry. Within aquaculture, using alternative prophylactic measures such as prebiotics to increase animal health and disease resistance could lead to the overall reduction of antibiotic use. Prebiotics are non-digestible food ingredients believed to help the beneficial bacteria within the intestinal track to grow. In turn, the increased numbers of beneficial bacteria reduce the possibility of pathogenic bacteria invading and establishing a presence in the intestinal track. The intestinal microbiome refers to the various organisms, such as bacteria, viruses, and fungi, that live commensally within the host digestive tract. The bacterial community within the intestinal microbiome has many important roles, including effects on host development, physiology, immunity, and nutrient acquisition. Many factors also impact the bacterial community, including the presence of pathogens and/or antibiotics, environmental conditions, host genetics, and the diet consumed. To promote environmental sustainability and improve production and animal health in aquaculture, a collaboration was created with Anheuser-Busch of the brewing industry and Maltento, a functional ingredient company. With breweries around the globe, Anheuser-Busch produces consistent, food grade byproducts that are safe for human consumption. Two of the most prevalent brewery byproducts are brewer's spent yeast (BSY) and brewer's spent grain (BSG). These low-value waste products can consequently be converted into high-value feed additives for use in aquaculture. The objective of the work presented in this thesis was to evaluate the effects of BSY and BSG-fed insect dietary feed additives on the production, health, and intestinal bacterial community of aquaculture-raised rainbow trout. Unintentionally, benefits of the feed additives on fish subjected to chronic and acute high-temperature thermal stress were also explored. Overall, the results of the study found that while the feed additives did not significantly increase the growth of the rainbow trout, benefits were still observed. When subjected to chronically high-water temperatures, fish fed the experimental diets outperformed those fed the control diet regarding growth parameters. The intestinal bacterial community of the fish was significantly altered from the beginning of the trial compared to the end of the trial, though differences are not believed to be caused by the feed additives. Instead, the resulting shift in the bacterial community is believed to have stemmed from the stress-response of the fish triggered by high water temperature. When the fish underwent an acute thermal stress event, which caused mortality, fish fed three of the five experimental diets were found to have higher survival rates compared to the control. Ultimately, results of this project suggest that the feed additives may have increased the health and robustness of the fish while undergoing thermal stress. However, further research under controlled conditions is needed to evaluate if the observed host health benefits can be attributed directly to the feed additives.

Graduation date: 1998