Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007. / Includes bibliographical references (leaf 31-34). / Introduction: Introduction: The world today contains an estimated 6.7 billion humans, and our population is growing at an unprecedented rate, consuming an ever-increasing amount of global resources. According to United Nations projections, the majority of this growth will occur in the third-world nations of Africa, and, to a lesser extent, Asia, among those peoples least able to afford the increasing burden on their resources. Clearly, what is needed in these African nations in the near future are more efficient, low-cost methods of using those resources they already have. Foremost among the problems faced by African developing nations is a lack of a reliable, sufficient, and nutritious food supply. Much of the African population survives on malnourished diets irregularly supplied by subsistence agriculture. In addition, crop loss due to both pests and post-harvest spoilage is much higher than in first world nations, with cold-storage technologies and modem pesticides. Equally important are the lives lost each year to food-borne disease. In the United States alone, food-borne infections cause an estimated 76 million cases of illness and 323,000 hospitalizations annually, for an estimated annual treatment cost of $6.7 billion and a death toll of thousands. In developing nations, of course, these casualty figures are much higher. It is precisely this crop loss and food-borne disease which this thesis proposes to address, by both proposing and evaluating a method, namely, food irradiation, to diminish crop loss in African villages and small-towns. As stated by Fritz Kaferstein in the Journal of Public Health Policy, "In developing countries with warm climates, with non-grain staples, vegetables and fruits, the pos-tharvest loss is believed to exceed 50%. With commodities such as dried fish, insect infestation is reported to result in a loss of 25% of the product with an additional 10% lost due to spoilage. While not all of these losses can be prevented by food irradiation, the technology does offer unique potential to destroy insect infestation and reduce spoilage." / by Nishaal Jitendra Parmar. / S.B.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 205-210). / This thesis presents the theory, design, and experimental demonstration of coherent microwave generation at 2.4 GHz in a metamaterial loaded waveguide using a 490 keV, 84 A, one microsecond pulse length electron beam that produced more than 5 MW of microwave power. Three different metamaterial structure designs named MTM1, MTM2, and MTM3 were tested with design frequencies of 2.8, 2.4, and 3.7 GHz, respectively. The waveguides were loaded with two metamaterial plates that were machined with complementary split ring resonators with periods ranging from 5 to 10 mm. The metamaterial waveguides supported two distinct modes: a symmetric mode that occurs when the two metamaterial plates were excited in phase, and an antisymmetric mode that occurs when the metamaterial plates were excited out of phase. The electron beam propagated on axis between the metamaterial plates. The output radiation was studied for solenoid magnetic field values in the range 350 to 1600 G and for beam voltages from 350 to 500 kV. The best results were found in a 370 mm long structure using the MTM2 design, where output power levels of up to 5 MW were obtained at 400 G in the antisymmetric mode at a frequency near 2.39 GHz. The frequency tuning vs. magnetic field for operation at a power level exceeding 1 MW was consistent with that predicted by an anomalous Doppler shifted resonance condition, [omega] = [kappa]z[upsilon]z - [Omega]c/[gamma]. At magnetic fields above 750 G, the microwave output switched to the symmetric mode at a frequency near 2.44 GHz, but the power level dropped drastically to below 100 W. In contrast to the antisymmetric mode, the frequency tuning of the symmetric mode was consistent with that predicted by a normal Cherenkov resonance, [omega] = [kappa]z[upsilonl]z. CST PIC simulations predict the observed output frequencies and the switch between modes at 750 G. However, the CST simulations also predict multi-megawatt power levels in both modes, which was observed in the antisymmetric mode, but not the symmetric mode. The discrepancy between the symmetric mode output power of the simulations and experiment Is unexplained. To the authors knowledge, these are the first reported experimental results of high power (> 1 MW) microwave generation from an electron beam interacting with a metamaterial structure. The results are important for the development of new microwave sources and novel devices which utilize active metamaterials / by Jason Samuel Hummelt. / Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 22-24). / Nuclear power is not as economically competitive as other electricity generation methods. To increase the use of nuclear power, nuclear power must become more profitable. A way to accomplish this is by storing superfluous energy during times of low energy prices to be used when the electricity price is greater. This could be done by varying the load to the turbine by diverting steam from before the turbine while the nuclear reactor runs at full power. In order to understand this project idea of diverting steam to a thermal storage to increase profit, literature on nuclear systems, steam turbines, and regulations was analyzed. It was found that between 40% and 75% of steam can be diverted from the secondary system of a pressurized water reactor. This number depends on the specific reactor and turbine system. The energy of the steam will be stored through a thermal storage method that can be directly or indirectly connected to the diverted steam. Each set-up comes with its advantages and disadvantages as adding a heat exchanger loses work, but would make regulatory considerations easier. / by Natalie J. Shifflet. / S.B.

Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007. / "June 2007." / Includes bibliographical references (leaves 127-139). / One of the largest oil reserves in the world is not in the Middle East or in Alaska, but in Canada. This fuel exists in the form of bitumen in Alberta's oil sands. While it takes a tremendous amount of energy to recover this bitumen and refine it into petroleum products, with oil prices nearing all time highs, it is profitable to do so. Oil sands recovery involves either strip mining the sands and extracting the oil, or pumping large quantities of steam into the ground in order to free the bitumen from the sand. Traditionally, the energy to produce the steam and hot water used in this process has come from natural gas. The use of natural gas for oil sands recovery presents a number of problems, among which are the environmental impact of the greenhouse gases and the price volatility of the natural gas market. This thesis explores the possibility of using nuclear energy to power oil sands recovery. Once operational, nuclear reactors produce no greenhouse gas emissions of carbon dioxide and offer relatively low and stable fuel and operation and maintenance costs. Uranium is not subject to the same market volatility as natural gas. There are, however, several trade-offs as well. This thesis compares the benefits and the drawbacks, and puts forth several complete scenarios for the introduction of nuclear technology into the oil sands recovery process. Nuclear energy used for steam production is found to be competitive with natural gas prices as low as $3.75/MMBtu (CAD). / (cont.) For electricity production, nuclear becomes competitive at natural gas prices of $8.50/MMBtu (CAD). The greenhouse gas impact of nuclear is to reduce emissions in the oil sands region, as much as 3.3 million metric tons per year avoided for a 100k barrel per day (bpd) bitumen production Steam Assisted Gravity Drainage (SAGD) facility, or 2.7 million metric tons per year for the replacement of 700MWe of grid electricity with nuclear power. For a steam supply scenario, the PBMR reactor is found to be well-sized to supply a 50,000 bpd SAGD plant, whereas the CANDU and ACR reactors considered are found to be too large, with too low pressure steam to be practical in that application. All of the reactors have potential for supplying heat and electricity for direct mining operations, however. In summary, nuclear energy applications appear to be well suited for long term oil sands production in an economically competitive, CO2 emission free way which would greatly help Canada in meeting its Kyoto greenhouse gas emission commitments and to continue responsible development of its rich oil sands resources. Chapter One lays out the background information regarding the basic methods of production used in the oil sands today and the technologies that are being studied for possible future use. / (cont.) Chapter Two describes the challenges that face the oil sands industry in the current development environment, while Chapter Three details the energy requirements of the oil sands industry and surveys the energy generation options available in the region. Chapter Four provides a description of the reactors that have been suggested for this application, and sets out their steam capacities for the SAGD application. Chapter Five proposes a set of possible scenarios for integrating nuclear energy into oil sands projects and sets forth the steps that need to be taken to accomplish that integration, as well as the requisite benefits and economic implications of doing so. Finally, Chapter 6 concludes with a discussion of the results and makes recommendations for future work. / by Ashley Finan. / S.M.and S.B.

Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2018. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 52-54). / X-ray imaging is a core component of our modern medical diagnosis arsenal in combatting a broad range of disease. X-ray imaging allows medical professionals to see the internal structure and layout of the human body, and in this way allows for the visualization of unseen ailments. A current "disease of poverty" which is the target of this study is tuberculosis, a lung bacteria which is visible on x-ray imaging. X-ray imaging is a well known and used technology, yet x-ray imaging remains very expensive and unwieldy for use in less-developed regions of the world. Within the last three to four decades, the world has seen a massive explosion in consumer camera technology development, largely driven by circuit miniaturization, and this has led to cheaper and higher resolution cameras being produced. X-ray images themselves rely on a material to turn x-rays, the photons which pass through the person in medical imaging, into electrical signals which can be read by a computer. This collection of x-ray photons can be done through the coupling of a scintillating screen and a camera which images the scintillating screen to create an x-ray image. This study explores this particular method of x-ray imaging which is likely to be cheaper than existing methods of x-ray imaging, yet also likely yields images of poorer resolution and contrast distinction in x-ray images. The theoretical components necessary to setup such a system in the most efficient manner possible were analyzed, taking into consideration safety and finance constraints. The imaging capabilities of a Nikon D810 (f/1.4, 50 mm lens) and iPhone 5S (f/2.2 lens), higher and lower quality cameras respectively, were analyzed using three scintillating screens, the MCI Optonix DRZ High, Scintacor DRZ Medium, and Scintacor DRZ Ultrafine screens, to capture the x-rays produced from a 14 mA 100 kV x-ray tube. It was found that the Nikon D810 coupled with the MCI Optonix DRZ High Screen produced results similar in performance to current medical imaging, and the iPhone 5S images were too noisy to be conclusive. Further work should go into developing a more finalized and standalone product that can be tested in clinically important settings, as this study does provide the proof-of-concept framework for this to be possible. / by Logan B. Abel. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006. / Includes bibliographical references (p. 62). / Perfect plant operation with high safety and economic performance is based on both good physical design and successful organization. However, in comparison with the affection that has been paid to technology research, the effort that has been exerted to enhance NPP management and organization, namely human performance, seems pale and insufficient. There is a need to identify and assess aspects of human performance that are predictive of plant safety and performance and to develop models and measures of these performance aspects that can be used for operation policy evaluation, problem diagnosis, and risk-informed regulation. The challenge of this research is that: an NPP is a system that is comprised of human and physics subsystems. Every human department includes different functional workers, supervisors, and managers; while every physical component can be in normal status, failure status, or a being-repaired status. Thus, an NPP's situation can be expressed as a time-dependent function of the interactions among a large number of system elements. The interactions between these components are often non-linear and coupled, sometime there are direct or indirect, negative or positive feedbacks, and hence a small interference input either can be suppressed or can be amplified and may result in a severe accident finally. This research expanded ORSIM (Nuclear Power Plant Operations and Risk Simulator) model, which is a quantitative computer model built by system dynamics methodology, on human reliability aspect and used it to predict the dynamic behavior of NPP human performance, analyze the contribution of a single operation activity to the plant performance under different circumstances, diagnose and prevent fault triggers from the operational point of view, and identify good experience and policies in the operation of NPPs. / (cont.) Regarding the human reliability analysis function, the partial Standardized Plant Analysis Risk Human Reliability Analysis (SPAR-H) method was applied. Performance Shaping Factors (PSFs) were employed to analyze the influence of human performance indicators already existing in ORSIM. Based on the human performance model, an operation case study was investigated. A series of carefully chosen candidate policies were tested on a computerized model that represents the structure, processes, and interactions of the underlying target NPP systems. These candidates included: (1) New management system application; (2) Personnel population change, (3) Planning delay, and (4) Tolerance to surprise workload. / by Xinyuan Chu. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 195-204). / In this thesis, two experimental investigations are presented in an attempt to understand the loss of lower hybrid current drive (LHCD) efficiency in reactor-relevant, high-density plasmas on the diverted Alcator C-Mod tokamak. While the previous work has identified that edge interactions, such as collisional absorption and excessive up-shift of the parallel refractive index due to full-wave effects, could potentially explain the observed loss of LHCD efficiency in a wide range of line-averaged densities, these simulations still over-predict the fast electron population generated by LHCD above line-averaged densities of 1 x 10²⁰ m- ³. It is critical to identify remaining mechanisms in order to demonstrate advanced tokamak operation at reactor-relevant densities. The first investigation is to perform microwave backscattering experiments to detect electrostatic lower hybrid (LH) waves in the scrape-off layer (SOL), where a significant amount of the injected LH power may be deposited due to a number edge loss mechanisms. An existing ordinary-mode (O-mode) reflectometer system has been modified to measure the backscattered O-mode wave as a result of Bragg backscattering of the incident O-mode wave off the LH wave. The detection of LH waves in a region that is not magnetically connected to the launcher implies a weak single pass absorption of LH waves in high density plasmas. The observed spectral width of the backscattered signals indicates the presence of non-linear effects on the propagation of LH waves, but no experimental evidence is found to confirm whether the non-linear mechanism that is responsible for the observed spectral broadening is responsible for the observed loss of LHCD efficiency. The second investigation is to examine the change in LH frequency spectra due to density-dependent non-linear effects, such as parametric decay instability (PDI) above the line-averaged density of 1 x 10²⁰ m-³, using the probes installed on the launcher, outer divertor, and inner wall. Ion cyclotron PDI is found to be excited above line-averaged densities of 1 x 10²⁰ m -³, suggesting that ion cyclotron PDI may be a remaining mechanism to understand the loss of LHCD efficiency. Ion cyclotron PDI is observed to be excited not only at the low-field-side edge but also at the high-field-side (HFS) edge of Alcator C-Mod, further corroborating that LH waves are weakly absorbed on their first pass. Evidence of pump depletion is found with the onset of ion cyclotron PDI at the HFS edge in lower-single-null plasmas. However, no apparent pump depletion is seen when the magnetic geometry is switched to an upper-single-null. Moreover, ion cyclotron PDI is excited at the LFS edge in this case. Thus, the role of the observed ion cyclotron PDI on the loss of LHCD efficiency needs further experimental investigation to be conclusive due to the different ion cyclotron PDI strength and excitation location, depending on magnetic configurations. A summary of the new findings of this thesis is as follows: First measurements of PDI below the classical threshold (wo/wLH(0) ~~ 2). First ever observation of PDI on HFS of a tokamak and its relationship to being in a multi-pass damping regime. " Advancement of PDI as a candidate mechanism for the LHCD density limit. / by Seung Gyou Baek. / Ph. D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008. / Includes bibliographical references (leaves 26-27). / MicroPET imaging studies were conducted to investigate the role of metabotropic glutamate subtype-5 receptors (mGluR5) in Parkinson's disease (PD). Four analogical PET ligands were used to characterize modulation of mGluR5 function in a 6hydroxydopamine (6-OHDA) induced rat model of PD. Unilateral 6-OHDA lesions were made in the right medial forebrain bundle, and severity of these lesions was determined with [¹¹]CFT. The binding characteristics of the PET ligands were analyzed using a modified distribution volume method of the Logan reference region model. Binding potential values were calculated on the striatum, hippocampus, and cortex, using the cerebellum as a reference tissue. On the right (with lesion) side of the striatum, ["C]CFT binding decreased. Three of the four investigated mGluR5 ligands ([¹¹C]MPEP, [¹¹C]M-PEPy, and [¹¹C]MMPEP) also showed enhanced binding characteristics on the same side of the brain. The right hippocampus and cortex showed similar results. The mGluR5s' enhanced binding characteristics on the right side of the brain suggest a complementary and compensatory role of metabotropic glutamate receptors in the dopaminergic neurodegeneration of Parkinson's disease. / by Peter Lamb. / S.B.

Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 61-63). / Monte Carlo methods for reactor analysis have been in development with the eventual goal of full-core analysis. To attain results with reasonable uncertainties, large computational resources are needed. Variance reduction methods have been developed in order to reduce the computational resources required to obtain results in a practical amount of time. This work seeks to expand research in the Uniform Fission Site (UFS) method, a variance reduction technique recently developed that causes uniformity in uncertainty distributions by forcing uniformity in source distributions. This work aims to both improve the method as well as investigate its use with a source acceleration method, Coarse Mesh Finite Difference (CMFD) acceleration. Both techniques have been implemented into OpenMC, a continuous energy Monte Carlo code. The UFS method uses weights to alter the number of neutrons born at a fission site. It operates on a superimposed mesh, in which each mesh cell contains a different weight. These weights use an estimate of the source fraction and fuel volume fraction within the cell to produce uniformity. In current implementations, the fuel volumes are assumed to be dispersed equally over all mesh cells. This work aims to provide an estimate of the fuel volume fraction in each cell in order to improve the accuracy of the method for irregular geometries. The new fuel volume approximation method is tested on a toy problem and on a model of the Advanced Test Reactor, a core with highly irregular geometry. Figures of merit were calculated for a basic Monte Carlo simulation, a simulation with the standard UFS implementation, and the new UFS method with estimated volume fractions. With the toy problem, the new method showed significant improvement and had the highest figure of merit. In the case of the ATR, the long run time for the approximation lowered the figure of merit. Both problems demonstrated that the use of the standard UFS implementation on an irregular geometry produced higher uncertainties than not using the method at all. The UFS method, when used with the estimated volume fractions, behaved as expected and produced uniform uncertainty distributions. The investigation of the use of the UFS method with CMFD acceleration was conducted using the 3-D BEAVRS benchmark. Results showed that keeping CMFD acceleration on during active batches maintained a stationary source and reduced the variance for assembly results. The UFS method stacked on this, reducing the maximum relative uncertainties. The UFS method had variable results with different tallies, but no interference between the two methods was observed. / by Jessica Lynn Hunter. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2011. / Cataloged from PDF version of thesis. Page 125 blank. / Includes bibliographical references. / Cancer is a diverse disease with many manifestations. Various imaging modalities including magnetic resonance imaging (MRI) and positron emission tomography (PET) have been used to study human cancer. In this study, we developed integrated imaging techniques using advanced MR and PET to investigate potential biomarkers in glioblastoma (GBM). First, we applied proton magnetic resonance spectroscopy to assess the therapeutic effects of the new antiangiogenic drug (cedianib) on GBM. By evaluating changes in the levels of metabolites predominant in GBM during the treatment, we observed an antitumor response in GBM after one month. Notably, the index of the ratio of primary metabolites, NAA/Cho, in tumor strongly predicted 6-month overall survival; these data therefore suggest that NAA/Cho is the MRS-detectable biomarker that relates to tumor angiogenesis. Second, a simultaneous BOLD-ASL technique was investigated to measure the relative cerebral metabolic rate of oxygen (CMRO₂) in hyperoxia (i.e., CMRO₂/CMRO₂/₀) in GBM. Renewed interest in tumor metabolism, particularly in GBM, has recently prompted a re-examination of the Warburg effect. Our data have revealed that oxygen-induced CMRO₂ in tumor showed significant increase, supporting recent hypotheses on the preserved integrity of oxidative pathways in glycolytically active tumors. These data also propose a second remarkable biomarker for detecting tumor oxidative metabolic changes. Finally, and most importantly, we extended our earlier findings to explore the correlation between changes in oxidative metabolism and hypoxia level in GBM patients undergoing a multi-therapy treatment protocol by acquiring simultaneous MRI-PET data using our novel dual-modality MRPET imaging system. We observed an increase in relative CMRO₂ in regions showing high-level uptake of our ¹⁸F-MISO probe in pre-treated tumor, and a subsequent large reduction in both values with tumor regression following treatment. The consistency between tumor oxidative physiology and hypoxia assessed by our novel integrated imaging approach will be a good biomarker for detecting oxidative changes with therapeutic effects in gliomas. Overall, our integrated imaging methods offer great potential to move from the preliminary biomarker stage to later stages with more clearly established utility. With further investigation, these imaging tools could contribute in significant ways to the ongoing effort to reduce morbidity and mortality in cancer. / by Heisoog Kim. / Ph.D.