Nuclear energy is a source of carbon free power. With many countries striving to make deep carbon cuts in their energy sectors, nuclear energy could be a large part of the solution. One of the main obstacles standing in the way of the use of nuclear energy is the issue of used nuclear fuel disposal. According to the NEI, the U.S. creates about 2000 metric tons of used nuclear fuel per year and has generated around 76,000 metric tons of used nuclear fuel over the last 4 decades. While there are technical problems that need to be solved, it is primarily the public and political opposition to the disposal of used nuclear fuel that stands in the way of progress in this area. This work addresses this issue through Multi-Criteria Decision Analysis (MCDA). To make a decision among ten different fuel cycles, we have brought together five stakeholders: Nuclear Scientists and Engineers, Environmental Scientists, Economists, Political Scientists, and The General Public. Using Multi-Attribute Value Theory (MAVT), we have been able to develop decision models for each stakeholder as well as a model that combines them all and came to the conclusion that of the ten fuel cycles considered, the best decision is to continue to use On Site Dry Cask Storage. This decision is made with small sample sizes but the methodology could be applied at much larger scales and can potentially be used to choose a fuel cycle that encounters much less political and social opposition to its implementation.

Este trabalho apresenta uma nova metodologia, simples e de baixo custo, para quantificação direta de urânio em compostos do ciclo do combustível nuclear, baseada na espectroscopia no infravermelho com transformada de Fourier (FTIR), utilizando a técnica de pastilhamento em KBr. Diferentes matrizes foram utilizadas para o desenvolvimento e validação analítica: nitrato de uranilo complexado com TBP (UO2(NO3)2.2TBP) em fase orgânica e nitrato de uranilo (UO2(NO3)2) em fase aquosa. O método para matriz de urânio em fase orgânica (UO2(NO3)2.2TBP em hexano/incorporado em KBr) apresentou linearidade (r = 0,9980) dentro da faixa analítica de 0,20% 2,85% de urânio na pastilha de KBr, LD de 0,02% e LQ de 0,03%, exatidão com recuperações acima de 101,0%, robustez e precisão (DPR < 1,6%). O método para matriz de urânio em fase aquosa (UO2(NO3)2/incorporado em KBr) apresentou linearidade (r = 0,9900) dentro da faixa analítica de 0,14% 0,29% de urânio na pastilha de KBr, LD de 0,01% e LQ de 0,02%, exatidão com recuperações acima de 99,4%, robustez e precisão (DPR < 1,6 %). Amostras de processo do ciclo do combustível nuclear foram submetidas a avaliação intralaboratorial e os resultados foram comparados estatisticamente por outras técnicas: Espectrometria de Fluorescência de Raios-X (FRX) e gravimetria. Os testes estatísticos (t-Student e Fischer) indicaram que a técnica por FTIR e as de referência são equivalentes, demonstrando que a nova metodologia pode ser empregada com sucesso nas análises de rotina para o controle de qualidade dos compostos nucleares. / This work presents a low cost, simple and new methodology for direct quantification of uranium in compounds of the nuclear fuel cycle, based on Fourier Transform Infrared (FTIR) spectroscopy using KBr pressed discs technique. Uranium in different matrices were used to development and validation: UO2(NO3)2.2TBP complex (TBP uranyl nitrate complex) in organic phase and uranyl nitrate (UO2(NO3)2) in aqueous phase. The parameters used in the validation process were: linearity, selectivity, accuracy, limits of detection (LD) and quantitation (LQ), precision (repeatability and intermediate precision) and robustness. The method for uranium in organic phase (UO2(NO3)2.2TBP complex in hexane/embedded in KBr) was linear (r = 0.9980) over the range of 0.20% 2.85% U/ KBr disc, LD 0.02% and LQ 0.03%, accurate (recoveries were over 101.0%), robust and precise (RSD < 1.6%). The method for uranium aqueous phase (UO2(NO3)2/embedded in KBr) was linear (r = 0.9900) over the range of 0.14% 1.29% U/KBr disc, LD 0.01% and LQ 0.02%, accurate (recoveries were over 99.4%), robust and precise (RSD < 1.6%). Some process samples were analyzed in FTIR and compared with gravimetric and X-ray fluorescence (XRF) analyses showing similar results in all three methods. The statistical tests (t-Student and Fischer) showed that the techniques are equivalent. The validated method can be successfully employed for routine quality control analysis for nuclear compounds.

Este trabalho apresenta uma nova metodologia, simples e de baixo custo, para quantificação direta de urânio em compostos do ciclo do combustível nuclear, baseada na espectroscopia no infravermelho com transformada de Fourier (FTIR), utilizando a técnica de pastilhamento em KBr. Diferentes matrizes foram utilizadas para o desenvolvimento e validação analítica: nitrato de uranilo complexado com TBP (UO2(NO3)2.2TBP) em fase orgânica e nitrato de uranilo (UO2(NO3)2) em fase aquosa. O método para matriz de urânio em fase orgânica (UO2(NO3)2.2TBP em hexano/incorporado em KBr) apresentou linearidade (r = 0,9980) dentro da faixa analítica de 0,20% 2,85% de urânio na pastilha de KBr, LD de 0,02% e LQ de 0,03%, exatidão com recuperações acima de 101,0%, robustez e precisão (DPR < 1,6%). O método para matriz de urânio em fase aquosa (UO2(NO3)2/incorporado em KBr) apresentou linearidade (r = 0,9900) dentro da faixa analítica de 0,14% 0,29% de urânio na pastilha de KBr, LD de 0,01% e LQ de 0,02%, exatidão com recuperações acima de 99,4%, robustez e precisão (DPR < 1,6 %). Amostras de processo do ciclo do combustível nuclear foram submetidas a avaliação intralaboratorial e os resultados foram comparados estatisticamente por outras técnicas: Espectrometria de Fluorescência de Raios-X (FRX) e gravimetria. Os testes estatísticos (t-Student e Fischer) indicaram que a técnica por FTIR e as de referência são equivalentes, demonstrando que a nova metodologia pode ser empregada com sucesso nas análises de rotina para o controle de qualidade dos compostos nucleares. / This work presents a low cost, simple and new methodology for direct quantification of uranium in compounds of the nuclear fuel cycle, based on Fourier Transform Infrared (FTIR) spectroscopy using KBr pressed discs technique. Uranium in different matrices were used to development and validation: UO2(NO3)2.2TBP complex (TBP uranyl nitrate complex) in organic phase and uranyl nitrate (UO2(NO3)2) in aqueous phase. The parameters used in the validation process were: linearity, selectivity, accuracy, limits of detection (LD) and quantitation (LQ), precision (repeatability and intermediate precision) and robustness. The method for uranium in organic phase (UO2(NO3)2.2TBP complex in hexane/embedded in KBr) was linear (r = 0.9980) over the range of 0.20% 2.85% U/ KBr disc, LD 0.02% and LQ 0.03%, accurate (recoveries were over 101.0%), robust and precise (RSD < 1.6%). The method for uranium aqueous phase (UO2(NO3)2/embedded in KBr) was linear (r = 0.9900) over the range of 0.14% 1.29% U/KBr disc, LD 0.01% and LQ 0.02%, accurate (recoveries were over 99.4%), robust and precise (RSD < 1.6%). Some process samples were analyzed in FTIR and compared with gravimetric and X-ray fluorescence (XRF) analyses showing similar results in all three methods. The statistical tests (t-Student and Fischer) showed that the techniques are equivalent. The validated method can be successfully employed for routine quality control analysis for nuclear compounds.

The closure of the nuclear fuel cycle is a topic of interest in the sustainability context of nuclear energy. The implication of such closure includes considerations of nuclear waste management. This originates from the fact that a closed fuel cycle requires recycling of useful materials from spent nuclear fuel and discarding of non-usable streams of the spent fuel, which are predominantly the fission products. The fission products represent the near-term concerns associated with final geological repositories for the waste stream. Long-lived fission products also contribute to the long-term concerns associated with such repository. In addition, an ultimately closed nuclear fuel cycle in which all actinides from spent nuclear fuels are incinerated will result in fission products being the only source of radiotoxicity. Hence, it is desired to develop a transmutation strategy that will achieve reduction in the inventory and radiological parameters of significant fission products within a reasonably short time. In this dissertation, a transmutation strategy involving the use of the VHTR is developed. A set of specialized metrics is developed and applied to evaluate performance characteristics. The transmutation strategy considers six major fission products: 90Sr, 93Zr, 99Tc, 129I, 135Cs and 137Cs. In this approach, the unique core features of VHTRs operating in equilibrium fuel cycle mode of 405 effective full power days are used for transmutation of the selected fission products. A 30 year irradiation period with 10 post-irradiation cooling is assumed. The strategy assumes no separation of each nuclide from its corresponding material stream in the VHTR fuel cycle. The optimum locations in the VHTR core cavity leading to maximized transmutation of each selected nuclides are determined. The fission product transmutation scenarios are simulated with MCNP and ORIGEN-S. The results indicate that the developed fission product transmutation strategy offers an excellent potential approach for the reduction of inventories and radiological parameters, particularly for long-lived fission products (93Zr, 99Tc, 129I and 135Cs). It has been determined that the in-core transmutation of relatively short-lived fission products (90Sr and 137Cs) has minimal advantage over a decay-only scenario for these nuclides. It is concluded that the developed strategy is a viable option for the reduction of radiotoxicity contributions of the selected fission products prior to their final disposal in a geological repository. Even in the cases where the transmutation advantage is minimal, it is deemed that the improvement gained, coupled with the virtual storage provided for the fission products during the irradiation period, makes the developed fission product transmutation strategy advantageous in the spent fuel management scenarios. Combined with the in-core incineration options for TRU, the developed transmutation strategy leads to potential achievability of engineering time scales in the comprehensive nuclear waste management.

Determining the cost of implementing a nuclear energy policy is very important due to the high costs associated with nuclear programs. Such programs may be unattainable to certain countries due to the many requirements that ensure a safe and secure nuclear sector. The IAEA has a large number of publications that indicate the requirements for implementing nuclear energy sectors. By using these publications, a framework was developed costing each of the main sectors of a nuclear energy program. These sectors correspond to the sectors that the South African government proposed for its nuclear energy policy. The main sectors are: * Basic infrastructure development * Nuclear power plant (NPP) sector * Nuclear fuel cycle (NFC) sector * Industrial involvement An outline of the framework is attached as Appendix A. A more elaborative development of the framework is given in Chapter 2. The Government proposes the development of 20 GWe (Eskom Holdings Limited, 2010:3) of nuclear power over the next 20 to 25 years along with the development of the entire nuclear fuel cycle and an industrial base that will ensure that South Africa is independent of other countries and has the capability to develop nuclear power plants and associated technology. By applying the framework it was possible to estimate the costs of the different sectors. It was found by the author that the basic infrastructure and power plant sector will cost approximately R 889 billion (2008 Rand value), excluding financing costs. The fuel cycle sector is very sensitive to global resistance and will require considerable planning to ensure that international bodies and countries are satisfied with the local intention of pursuing fuel cycle implementation. To ensure that costs are minimized the implementation of the different fuel cycle steps is crucial and will depend on the rollout plan of the power plants and the local demand for fuel and the influence of security of fuel supply. To implement the entire front end and reprocessing step it was estimated that the cost will amount to approximately R 52,3 billion. The cost of implementing the industrial sector development was not determined, due to the many factors involved. The different requirements in the sector may be supplied by similar industries currently active in South Africa. Most of the current industries will require further accreditation and may have to increase capacity if South Africa is to become a global supplier of nuclear technology. Sources indicated that the different sectors will require trained personnel numbers in the region of 77 000 (direct jobs). The amount of indirect jobs that will be created will be in the regions of 300 000. Government therefore has a huge responsibility to ensure that training and education programs are developed that can supply the demand of trained personnel. The different industries involved should also ensure that the relevant personnel are trained in advance, to obtain the required accreditation and experience. The final outcome of the revised Integrated Resource Plan (IRP2) was not yet available when this dissertation was completed. The outcomes of the future nuclear programs may therefore be different from the extent of developments and investments estimated by this study. The cost of reactors and basic infrastructure will have to be scaled to the revised objectives while the costs of the fuel cycle may change considerably due to a possible decrease in local demand. These changes will affect the economy of scale on many of the sectors of development. The framework is generic and may be applied to different nuclear development programs and countries. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Determining the cost of implementing a nuclear energy policy is very important due to the high costs associated with nuclear programs. Such programs may be unattainable to certain countries due to the many requirements that ensure a safe and secure nuclear sector. The IAEA has a large number of publications that indicate the requirements for implementing nuclear energy sectors. By using these publications, a framework was developed costing each of the main sectors of a nuclear energy program. These sectors correspond to the sectors that the South African government proposed for its nuclear energy policy. The main sectors are: * Basic infrastructure development * Nuclear power plant (NPP) sector * Nuclear fuel cycle (NFC) sector * Industrial involvement An outline of the framework is attached as Appendix A. A more elaborative development of the framework is given in Chapter 2. The Government proposes the development of 20 GWe (Eskom Holdings Limited, 2010:3) of nuclear power over the next 20 to 25 years along with the development of the entire nuclear fuel cycle and an industrial base that will ensure that South Africa is independent of other countries and has the capability to develop nuclear power plants and associated technology. By applying the framework it was possible to estimate the costs of the different sectors. It was found by the author that the basic infrastructure and power plant sector will cost approximately R 889 billion (2008 Rand value), excluding financing costs. The fuel cycle sector is very sensitive to global resistance and will require considerable planning to ensure that international bodies and countries are satisfied with the local intention of pursuing fuel cycle implementation. To ensure that costs are minimized the implementation of the different fuel cycle steps is crucial and will depend on the rollout plan of the power plants and the local demand for fuel and the influence of security of fuel supply. To implement the entire front end and reprocessing step it was estimated that the cost will amount to approximately R 52,3 billion. The cost of implementing the industrial sector development was not determined, due to the many factors involved. The different requirements in the sector may be supplied by similar industries currently active in South Africa. Most of the current industries will require further accreditation and may have to increase capacity if South Africa is to become a global supplier of nuclear technology. Sources indicated that the different sectors will require trained personnel numbers in the region of 77 000 (direct jobs). The amount of indirect jobs that will be created will be in the regions of 300 000. Government therefore has a huge responsibility to ensure that training and education programs are developed that can supply the demand of trained personnel. The different industries involved should also ensure that the relevant personnel are trained in advance, to obtain the required accreditation and experience. The final outcome of the revised Integrated Resource Plan (IRP2) was not yet available when this dissertation was completed. The outcomes of the future nuclear programs may therefore be different from the extent of developments and investments estimated by this study. The cost of reactors and basic infrastructure will have to be scaled to the revised objectives while the costs of the fuel cycle may change considerably due to a possible decrease in local demand. These changes will affect the economy of scale on many of the sectors of development. The framework is generic and may be applied to different nuclear development programs and countries. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Various fuel cycles for a sodium-cooled, subcritical, fast reactor with a fusion neutron source for the transmutation of light water reactor spent fuel have been analyzed. All fuel cycles were 4-batch, and all but one were constrained by a total fuel residence time consistent with a 200 dpa clad and structure materials damage limit. The objective of this study was to achieve greater than 90% burn up of the transuranics from the spent fuel.

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