Browsing by Subject "nuclear"
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Item Characterization of a novel pro-apoptotic role for nuclear associated BCL-2(2006-11-03) Bryce Patrick Portier; Giulio Taglialatela; Shawn Newlands; Jeffery Ceci; Jay Foreman; Gracie VargasBoth stroke and cancer are major public health problems that inflict immeasurable suffering to victims and their families. The treatment options currently in place for both stroke victims and cancer patients are limited. The underlying unifying characteristic of both conditions is that they are the end result of abrogation of apoptosis regulation. In the case of stroke, an initial increase in Bcl-2 expression traditionally follows ischemia/re-perfusion. A major goal of stroke therapy is to rescue the peri-ischemic region of cells that have up-regulated Bcl-2 but have not yet committed to the execution phase of apoptosis. A strong potential target to save neurons and supporting glia is to modulate Bcl-2 expression or localization in order to promote an anti-apoptotic function. Likewise, in the case of cancer, 80% of all tumors over-express Bcl-2. While malignant cells utilize mitochondrial localized Bcl-2 to gain protection from apoptosis, possession of Bcl-2 makes these cells a target for treatments that could alter Bcl-2’s localization and potentially promote apoptosis by altering Bcl-2’s sub-cellular localization/function. Thus, my Ph.D. project has focused on understanding the role of nuclear localized Bcl-2, Bcl-2’s default sub-cellular localization, and on the mechanism of binding between Bcl-2 and its mitochondrial chaperone protein FKBP38. My work has characterized the function of nuclear-associated Bcl-2 as a pro-apoptotic protein and Bcl-2’s BH4 domain as a critical domain for binding the chaperone protein FKBP38. Based on these findings we attempted a strategy for interfering with Bcl-2/FKBP38 binding via addition of a BH4 domain peptide both in vivo and in vitro. In both cases, addition of a BH4 domain peptide disrupted Bcl-2/FKBP38 binding, increased the level of nuclear associated Bcl-2, and induced apoptosis selectively in Bcl-2 bearing cells. The rationale behind this project was to determine molecular events underscoring Bcl-2’s localization and function in order to identify novel therapeutic targets for treatment of conditions that would benefit from interventions that modify the execution of apoptosis. The long term goal spawning from my Ph.D. thesis project is to further our understanding of apoptotic control mechanisms and in turn develop future therapies to control diseases due to abrogation of apoptotic regulation.Item Development of MELCOR Input Techniques for High Temperature Gas-Cooled Reactor Analysis(2011-08-08) Corson, JamesHigh Temperature Gas-cooled Reactors (HTGRs) can provide clean electricity,as well as process heat that can be used to produce hydrogen for transportation and other sectors. A prototypic HTGR, the Next Generation Nuclear Plant (NGNP),will be built at Idaho National Laboratory.The need for HTGR analysis tools and methods has led to the addition of gas-cooled reactor (GCR) capabilities to the light water reactor code MELCOR. MELCOR will be used by the Nuclear Regulatory Commission licensing of the NGNP and other HTGRs. In the present study, new input techniques have been developed for MELCOR HTGR analysis. These new techniques include methods for modeling radiation heat transfer between solid surfaces in an HTGR, calculating fuel and cladding geometric parameters for pebble bed and prismatic block-type HTGRs, and selecting appropriate input parameters for the reflector component in MELCOR. The above methods have been applied to input decks for a water-cooled reactor cavity cooling system (RCCS); the 400 MW Pebble Bed Modular Reactor (PBMR), the input for which is based on a code-to-code benchmark activity; and the High Temperature Test Facility (HTTF), which is currently in the design phase at Oregon State University. RCCS results show that MELCOR accurately predicts radiation heat transfer rates from the vessel but may overpredict convective heat transfer rates and RCCS coolant flow rates. PBMR results show that thermal striping from hot jets in the lower plenum during steady-state operations, and in the upper plenum during a pressurized loss of forced cooling accident, may be a major design concern. Hot jets could potentially melt control rod drive mechanisms or cause thermal stresses in plenum structures. For the HTTF, results will provide data to validate MELCOR for HTGR analyses. Validation will be accomplished by comparing results from the MELCOR representation of the HTTF to experimental results from the facility. The validation process can be automated using a modular code written in Python, which is described here.Item Development of Spatio-Temporal Wavelet Post Processing Techniques for Application to Thermal Hydraulic Experiments and Numerical Simulations(2012-07-16) Salpeter, NathanielThis work focuses on both high fidelity experimental and numerical thermal hydraulic studies and advanced frequency decomposition methods. The major contribution of this work is a proposed method for spatio-temporal decomposition of frequencies present in the flow. This method provides an instantaneous visualization of coherent frequency ?structures? in the flow. The significance of this technique from an engineering standpoint is the ease of implementation and the importance of such a tool for design engineers. To validate this method, synthetic verification data, experimental data sets, and numerical results are used. The first experimental work involves flow through the side entry orifice (SEO) of a boiling water reactor (BWR) using non-intrusive particle tracking velocimetry (PTV) techniques. The second experiment is of a simulated double ended guillotine break in the prismatic block gas cooled reactor. Numerical simulations of jet flow mixing in the lower plenum of a prismatic block high temperature gas cooled reactor is used as a final data set for verification purposes as well as demonstration of the applicability of the method for an actual computational fluid dynamics validation case.Item Development of the fundamental attributes and inputs for proliferation resistance assessments of nuclear fuel cycles(Texas A&M University, 2007-09-17) Giannangeli, Donald D. J., IIIRobust and reliable quantitative proliferation resistance assessment tools are critical to a strengthened nonproliferation regime and to the future deployment of nuclear fuel cycle technologies. Efforts to quantify proliferation resistance have thus far met with limited success due to the inherent subjectivity of the problem and interdependencies between attributes that contribute to proliferation resistance. This work focuses on the diversion of nuclear material by a state and defers other threats such as theft or terrorism to future work. A new approach is presented that assesses the problem through four stages of proliferation: the diversion of nuclear material, the transportation of nuclear material from an internationally safeguarded nuclear facility to an undeclared facility, the transformation of material into a weapons-usable metal, and weapon fabrication. A complete and concise set of intrinsic and extrinsic attributes of the nation, facility and material that could impede proliferation are identified. Quantifiable inputs for each of these attributes are defined. For example, the difficulty of handling the diverted material is captured with inputs like mass and bulk, radiation dose, heating rate and others. Aggregating these measurements into an overall value for proliferation resistance can be done in multiple ways based on well-developed decision theory. A preliminary aggregation scheme is provided along with results obtained from analyzing a small spent fuel reprocessing plant to demonstrate quantification of the attributes and inputs. This quantification effort shows that the majority of the inputs presented are relatively straightforward to work with while a few are not. These few difficult inputs will only be useful in special cases where the analyst has access to privileged, detailed or classified information. The stages, attributes and inputs of proliferation presented in this work provide a foundation for proliferation resistance assessments which may use multiple types of aggregation schemes. The overall results of these assessments are useful in comparing nuclear technologies and aiding decisions about development and deployment of that technology.Item Hydride production in zircaloy-4 as a function of time and temperature(2009-05-15) Parkison, Adam JosephThe experiments performed for this thesis were designed to define the primary process variables of time, temperature, and atmosphere for an engineering system that will produce metal powder from recycled nuclear fuel cladding. The proposed system will hydride and mill Zircaloy cladding tubes to produce fine hydride powder and then dehydride the powder to produce metal; this thesis is focused on the hydride formation reaction. These experiments were performed by hydriding nuclear grade Zircaloy-4 tubes under flowing argon-5% hydrogen for various times and temperatures. The result of these experiments is a correlation which relates the rate of zirconium hydride formation to the process temperature. This correlation may now be used to design a method to efficiently produce zirconium hydride powder. It was observed that it is much more effective to hydride the Zircaloy-4 tubes at temperatures below the a-B-d eutectoid temperature of 540?C. These samples tended to readily disassemble during the hydride formation reaction and were easily ground to powder. Hydrogen pickup was faster above this temperature but the samples were generally tougher and it was difficult to pulverize them into powder.Item Impact of Climate Change on Long Term Nuclear Power Plant Operation(2010-10-12) Redwine, Adam B.The present work examines the potential impact of changes in climatic conditions on the long-term functioning of nuclear power plants. Nuclear power plants are potentially susceptible to changes both in acute risks, such as severe storm events, and chronic risks, such as detrimental changes in the thermodynamics of plant operation. Extending plant lifetimes well beyond the lengths of operation for which they were originally designed suggests the necessity of studying the impacts such changes might have. Potential threats are examined in light of earlier work performed by Business Continuity Consulting on commission for Enteritgy Nuclear. The fourteen risk drivers identified in that work as threats warranting additional investigation are studied individually, and their relevance and likely impact extrapolated for regions covered by the ten selected sites under examination. Thermodynamic eff ects are simulated with a plant analysis program known as PEPSE (Performance Evaluation of Plant Systems Efficiencies), with which a broad range of modeled environmental and plant conditions are analyzed for potential impacts to plant functioning. Of the fourteen climatic risk drivers considered, changes in drought and ood severity and frequency resulting from climate change were determined to be the most likely detriments to plant operations. Precipitation gures indicate that plants located in the Midwest are particularly susceptible to future drought conditions while those in the Northeast are likely to experience more frequent ooding. Many of the risk drivers specifi ed by the earlier work were only cursorily examined in light of the complex nature of these phenomena and lack of well defi ned correlation to climate change. Other risks were analyzed using the gathered data, but were determined not to pose signi ficant threats to plant operations. In addition to large scale climatic e ffects, changes related to coolant uid temperature rise and plant component efficiency were examined to qualify their e ect on the thermodynamics of the model plant. Plant operating conditions were modeled for a wide range of conditions related to theoretical environmental changes. These examinations showed negligibly small impacts caused by increased coolant water temperature and moderate impact caused by changes in air humidity.Item Multiphysics Design and Simulation of a Tungsten-Cermet Nuclear Thermal Rocket(2012-10-19) Appel, BradleyThe goal of this research is to apply modern methods of analysis to the design of a tungsten-cermet Nuclear Thermal Rocket (NTR) core. An NTR is one of the most viable propulsion options for enabling piloted deep-space exploration. Concerns over fuel safety have sparked interest in an NTR core based on tungsten-cermet fuel. This work investigates the capability of modern CFD and neutronics codes to design a cermet NTR, and makes specific recommendations for the configuration of channels in the core. First, the best CFD practices available from the commercial package Star-CCM+ are determined by comparing different modeling options with a hot-hydrogen flow experiment. Next, through grid convergence and sensitivity studies, numerical uncertainty is shown to be a small contributor to overall uncertainty; while fuel thermal conductivity, hydrogen specific heat, and fission energy deposition are found to have a large impact on simulation uncertainty. The model-form error is then estimated by simulation of a NERVA fuel element from an NRX-A6 engine test, where the peak temperature matches measured data to within 2.2%. Using a combination of Star-CCM+ and MCNP for neutronics, typical uncertainties are estimated at 3% for predicting fuel temperature, 2% for hydrogen temperature, and 5% for pressure. The second part uses the aforementioned analysis methods in a parametric study to determine what coolant channel size and distribution is optimum for a 10 klbf-thrust cermet NTR core. By varying the channel diameter and pitch-to-diameter ratio (p/d), it is found that a diameter of 0.12 cm with a p/d of 1.8 results in the lightest core with a peak temperature of 2850 K. The study also shows that element-by-element mass flow rate zoning is the best method for handling radial power peaking. In addition, a detailed simulation of a cermet design developed at the Argonne National Laboratory shows that modifications to the historical fuel element design are required to avoid overheating. The final part investigates the ability of Star-CCM+ to model fuel element failure modes. Through a combination of uncertainty quantification and a parametric analysis, this thesis ultimately lays a groundwork for future detailed design of cermet NTR fuel elements.Item N/z equilibration in deep inelastic collisions and the fragmentation of the resulting quasiprojectiles(Texas A&M University, 2007-09-17) Keksis, August LawrenceWhen target and projectile nuclei have a difference in neutron to proton ratio (N/Z), the quasiprojectiles formed in a deep inelastic collision (DIC) should have a mean N/Z between the N/Z of the target and the N/Z of the projectile, depending on the amount of N/Z equilibration that occurred. Data from six reaction systems at two beam energies (32 and 45 MeV/nucleon) were collected. The systems in order of increasing difference between target and projectile N/Z (shown in parentheses) are 40Ar + 112Sn (??????N/Z = 0.018), 48Ca + 124Sn (??????N/Z = 0.080), 48Ca + 112Sn (??????N/Z = 0.160), 40Ca + 112Sn (??????N/Z = 0.240), 40Ar + 124Sn (??????N/Z = 0.258) and 40Ca + 124Sn (??????N/Z = 0.480). The quasiprojectile N/Z was determined by two techniques. The first technique used the isotopically resolved fragments to reconstruct the quasiprojectile N/Z. The second technique, developed in this thesis, used fragment yield ratios and a simple equation to simultaneously fit all six systems to determine the quasiprojectile N/Z. Simulations and a filter of the FAUST (Forward Array Using Silicon Technology) acceptance were used to calculate neutron loss; this accounted for the difference between the two techniques. To study the fragmentation of quasiprojectiles the fragment yields were used to calculate the isobaric, isotopic, fractional and mean N/Z yields. The results showed that as neutron richness increased, more neutron-rich fragments were produced. In addition observation showed evidence for an inhomogeneous distribution of N/Z between the light charged particles (LCPs Z less than 3) and intermediate mass fragments (IMFs Z greater than 2). The theoretical results, which used different values of the symmetry energy, were compared to experimental data to determine which symmetry energy best represents the experimental data. The comparison showed the experimental data was the overall best fit with a lower value of the symmetry energy. These results were not conclusive and further investigation is required.Item Nationwide Used Fuel Inventory Analysis(2013-11-27) Yancey, KristinaThe goal of this research was to develop a methodology to collect inventory estimates for the analysis and characterization of used fuel in the United States. To accomplish this, the Spent Fuel Database (SFD) was created. Data was collected for the database from publicly available information on the 103 operating reactors in January 2012. Using this data, plant models were developed using ORIGEN-ARP, a point-depletion tool. The output for each reactor model included current inventory estimates for used fuel taken out of the reactor 0, 1, 3, 5, 10, and 20 years ago. To determine the applicability of the database, a methodology was developed to analyze and compare the SFD with mass values produced using knowledge of past fuel assembly designs for general reactor classes. The methodology was centered around the idea of the ?applicability range? (AR) of the database, which was defined as the degree to which a correct estimate can be made quantitatively. Pressurized Water Reactors (PWRs) were shown to have a much higher AR than Boiling Water Reactors (BWRs), and older assembly classes were shown to have a lower AR than newer classes. The fission products in the database were shown to consistently have a high AR. Berkelium and californium had low AR for all of the assembly classes, curium had low AR for BWR classes and mixed AR for PWR classes, and americium and some plutonium isotopes had low AR for BWR classes. An assessment of the inventory estimates considered the potential radiotoxicity and heat load from these masses. The radiotoxicity by ingestion decreased by about a factor of 10 from the newest used fuel to the oldest, and the radiotoxicity by inhalation decreased by a factor of 2. While one person could never eat or inhale a spent fuel assembly, radiotoxicity was used as a metric for the upper limit of possible harm. The heat load decreased by more than a factor of 100 over the same range of fuel assemblies. On a per assembly basis, the radiotoxicity and heat load showed similar trends, with newer PWR assemblies being the highest and BWR assemblies being the lowest in both categories. Considering these results, at a potential interim storage facility, priority should be given to the oldest BWR assemblies to reduce the radiotoxic risk and heating requirements. Also, reprocessing and transmuting is highly encouraged to reduce the radiotoxicity and heat of the waste entering storage. Finally, to continue improving the SFD, future work should seek to quantify the magnitude of the impact of variations in AR for curium and for BWR classes. Moreover, future work should incorporate the used fuel from all the shutdown reactors into the database. Even in its current form, though, the SFD is a useful reference tool.Item Radioactive Flow Characterization for Real-Time Detection Systems in UREX+ Nuclear Fuel Reprocessing(2011-02-22) Hogelin, Thomas RussellThe reprocessing of used nuclear fuel requires the dissolution and separation of numerous radioisotopes that are present as fission products in the fuel. The leading technology option in the U.S. for reprocessing is a sequence of processing methods known as UREX+ (Uranium Extraction ). However, an industrial scale facility implementing this separation procedure will require the establishment of safeguards and security systems to ensure the protection of the separated materials. A number of technologies have been developed for meeting the measurement demands for such a facility. This project focuses on the design of a gamma detection system for taking measurements of the flow streams of such a reprocessing facility. An experimental apparatus was constructed capable of pumping water spiked with soluble radioisotopes under various flow conditions through a stainless steel coil around a sodium iodide (NaI) detector system. Experiments were conducted to characterize the impact of flow rate, pipe air voids, geometry, and radioactivity dilution level on activity measurements and gamma energy spectra. Two coil geometries were used for these experiments, using 0.5 in stainless steel pipe wound into a coil with a 6 inch diameter; the first coil was 5.5 revolutions tall and the second coil was 9.5 revolutions tall. The isotopes dissolved in the flowing water were produced at the Texas A&M Nuclear Science Center via neutron activation of chromium, gold, cerium, and ytterbium nitrate salts. After activation, the salts were dissolved in distilled water and inserted into the radioactive flow assembly for quantitative measurements. Flow rate variations from 100 to 2000 ml/min were used and activity dilution levels for the experiments conducted were between 0.02 and 1.6 ?Ci/liter. Detection of system transients was observed to improve with decreasing flow rate. The detection limits observed for this system were 0.02 ?Ci/liter over background, 0.5% total activity change in a pre-spiked system, and a dilution change of 2% of the coil volume. MCNP (Monte Carlo N-Particle Transport) models were constructed to simulate the results and were used to extend the results to other geometries and piping materials as well as simulate actual UREX stream material in the system. The stainless steel piping for the flow around the detector was found to attenuate key identifying gamma peaks on the low end of the energy spectrum. For the proposed schedule 40 stainless steel pipe for an actual reprocessing facility, gamma rays below 100 keV in energy would be reduced to less than half their initial intensities. The exact ideal detection set up is largely activity and flow stream dependant. However, the characteristics best suited for flow stream detection are: 1) minimize volume around detector, 2) low flow rate for long count times, and 3) low attenuation piping material such as glass.Item Statewise Correlates of Civil Nuclear Energy(2014-08-01) Kafle, NischalQuantitative empirical analysis has been used in several works, over the past decade or so, to identify correlates of states motivation for pursuing military nuclear technology. Nelson and Sprecher used such methodology to identify various national attributes that correlate to states peaceful use of nuclear power for electricity generation, which was termed as \Nuclear Reliance." The major initial objective for the present work was to replace a dichotomous subjective independent variable used by Nelson and Sprecher to represent engagement in international commerce in civil nuclear technology with more objectively defined variables carrying a similar representation. Ordinary least squares stepwise regression was applied to a dataset consisting of 27 independent variables that was created for this study. Data for 13 of 27 independent variables were added to the dataset from previous study, and 9 of 14 previous attributes data were updated. Supervised stepwise regression was used to create a linear regression model with five predictors having acceptable confidence level (p < 0:01) and coefficient of determination (R^(2) ? 0:51). Results from stepwise linear regression showed that states that trade knowledge and material for nuclear power technology are heavily involved in civil nuclear power that states that are not involved in international trade of such technology and material. Analyses of the individual steps at several different levels of aggregation showed that some predictors were included as a consequence of improvements to residuals only for a few states. Preliminary results show that an analysis based on change from some prior year (1980 was used, for illustrative purposes) has considerable promise.Item Ternary Breaking of the Reaction System in Heavy-Ion Collisions below the Fermi Energy(2015-01-12) Cammarata, Paul JosephHeavy-ion collisions have played an important role in probing the asymmetry term of the nuclear Equation of State (nEoS). As the bombarding energy increases from lower energies (~9 MeV/nucleon) to near the Fermi energy, the reaction mechanism transitions from deep-inelastic transfer reactions to those resulting in the multi fragmentation of the reaction system. In the energy regime between the two extremes, there is the possibility of observing the dynamical breaking of the system into a few heavy reaction partners. This feature, regardless of the energy or asymmetry of the reacting system, has been predicted to be sensitive to the asymmetry term of the nEoS through a number of theoretical predictions. Recently, a new experiment has been conducted at the Texas A&M University Cyclotron Institute to explore the dynamical breaking of the reaction system at 15 MeV/nucleon. The reaction systems studied, 136Xe,124Sn+64Ni and 124Xe+58Ni, were chosen as they provide a wide range of isospin asymmetry. The forward array using silicon technology (FAUST) was coupled to a large quadrupole triplet spectrometer (QTS) to collect both the emitted intermediate mass fragments (Z ? 3) and the heavy, projectile-like remnant. This arrangement was designed, based on the predictions of numerous simulations, to be the most sensitive for detecting a three-body breakup of the reaction system. Previously, experimental observations have shown a strong angular alignment in the dynamical breakup of the hot, projectile-like source. In this experiment, a dependence on the charge and isospin asymmetry of the entrance channel in this energy regime is noted. A modest dependence on the mass and energy of the quasi-projectile (QP) source has been shown to play a significant role in understanding the angular distributions of the breakup. This dependence has been shown to act as a surrogate for the impact parameter of the collision. Additionally, the velocity of the resultant projectile-like fragment plays a key role in sorting out the dynamical vs. statistical breaking of the reaction system, especially when compared to experimentally filtered theoretical simulations (CoMD+Gemini). These dynamical events have revealed a neutron enrichment of the IMFs emitted from near the neck region, on short time scales, in good agreement with previously published data. The underlying shape of the hot QP has been predicted to be both sensitive to the asymmetry term of the nEoS and the driving force behind the few body breaking of the reaction system. Experimentally, being only able to detect the two resultant fragments of the QP breakup required the use of a surrogate method to qualitatively approximate the shape of the QP at the time of break-up. The dynamical events analyzed were, on average, the result of QPs with little deformation in velocity space. There was good agreement between the simulations and the experimental data. Recently, a machine learning algorithm has been tested in an attempt to consider multiple observables predicted to be sensitive to the symmetry energy concurrently. Initial testing of the algorithm proved promising, utilizing unfiltered results from dynamical simulations. This technique has been extended to experimentally filtered simulation data with statistically significant results. Within experimental detector constraints, the simulations retain enough sensitivity for the machine learning algorithm to discriminate between the parameterizations of the symmetry energy.