Characterization of sources of radioargon in a research reactor

textOn Site Inspection is the final measure for verifying compliance of Member States with the Comprehensive Nuclear-Test-Ban Treaty. In order to enable the use of ³⁷Ar as a radiotracer for On Site Inspection, the sources of radioargon background must be characterized and quantified. A radiation transport model of the University of Texas at Austin Nuclear Engineering Teaching Laboratory (NETL) TRIGA reactor was developed to simulate the neutron flux in various regions of the reactor. An activation and depletion code was written to calculate production of ³⁷Ar in the facility based on the results of the radiation transport model. Results showed ³⁷Ar production rates of (6.567±0.31)×10² Bq·kWh⁻¹ in the re- actor pool and the air-filled irradiation facilities, and (5.811±0.40)×10⁴ Bq·kWh⁻¹ in the biological shield. Although ⁴⁰Ca activation in the biological shield was found to dominate the total radioargon inventory, the contribution to the effluent release rate would be diminished by the immobility of Ar generated in the concrete matrix and the long diffusion path of mobile radioargon. Diffusion of radioargon out of the reactor pool was found to limit the release rate but would not significantly affect the integrated release activity. The integrated ³⁷Ar release for an 8 hour operation at 950 kW was calculated to be (1.05±0.8)×10⁷ Bq, with pool emissions continuing for days and biological shield emissions continuing for tens of days following the operation. Sensitivity analyses showed that estimates for the time-dependent concentrations of ³⁷Ar in the NETL TRIGA could be made with the calculated buildup coefficients or through analytical solution of the activation equations for only (n,[gamma]) reactions in stable argon or (n,[alpha]) reactions in ⁴⁰Ca. Analyses also indicated that, for a generalized system, the integrated thermal flux can be used to calculate the buildup due to air activation and the integrated fast flux can be used to calculate the buildup due to calcium activation. Based on the results of the NETL TRIGA, an estimate of the global research reactor source term for ³⁷Ar and an estimate of ground-level ³⁷Ar concentrations near a facility were produced.Mechanical Engineerin

Advancements in radionuclide monitoring technologies used to detect indications of nuclear explosions

The objective of the research documented in this dissertation was to advance the state-of-the-art radionuclide monitoring technologies used to detect indications of nuclear explosions, which are absolutely prohibited by the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Advancements are made in two areas. The first advancements are in the characterization and optimization of a Si-PIN diode-based radiation spectrometer prototype sensitive to both photons and conversion electrons. A novel peak-fitting algorithm referred to herein as the WiPFA algorithm was developed to support the Si-PIN diode spectrometer prototype characterization efforts. The absolute conversion electron detection efficiency of the prototype was found to be 5.2 ± 0.4 % at conversion electron energies near 150 keV, and the [superscript 131m]Xe, [superscript 133m]Xe, ¹³³Xe, and ¹³⁵Xe Minimum Detectable Concentrations (MDCs) were found to be 1.7, 2.0, 2.1, and 56 mBq-m⁻³, respectively. A series of Monte Carlo N-Particle (MCNP) radiation transport code models were then developed to evaluate the MDCs associated with a series of optimized Si-PIN diode-based spectrometer designs. These optimization studies revealed that coupling Si-PIN diodes available today with thinner, cylindrical spectrometer designs could reduce the [superscript 131m]Xe, [superscript 133m]Xe, and ¹³³Xe, MDCs to 0.48, 0.57, and 0.58 mBq-m⁻³, respectively. Subsequent studies utilizing larger, thicker Si-PIN diodes indicated that additional reductions down to 0.31, 0.37 and 0.37 mBq-m⁻³ might be possible. These small radioxenon MDCs coupled with other perceived advantages of Si-PIN diodes suggest that Si-PIN diode-based radiation spectrometers could serve as attractive alternatives to the high-resolution gamma-ray and beta-gamma coincidence spectrometers currently employed by the verification regime of the CTBT. The second area in which advancements are made is the radionuclide background activity concentration characterization area. The focus here is on CTBT-relevant radioactive particulates and noble gases produced via spontaneous fission and via naturally occurring cosmic-ray induced fission and activation reactions. A new application—the Terrestrial Xenon and Argon Simulator (TeXAS) application—was developed to streamline and automate the creation of high-fidelity MCNP models and dedicated nuclear data libraries required to support detailed, site-specific background activity concentration characterization studies. The capabilities of the TeXAS application are demonstrated and used to develop background activity concentration estimates specific to several layers of the Earth’s atmosphere, several subsurface depths in six geologies prevalent in the Earth’s upper crust, and seawater.Mechanical Engineerin

CAN-based Data Acquisition System for Hybrid Powertrain HIPPO-2

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Συστήματα Αυτοματισμού

Supporting real time video over ATM networks

Includes bibliographical references.In this project, we propose and evaluate an approach to delimit and tag such independent video slice at the ATM layer for early discard. This involves the use of a tag cell differentiated from the rest of the data by its PTI value and a modified tag switch to facilitate the selective discarding of affected cells within each video slice as opposed to dropping of cells at random from multiple video frames

Characterization of response properties and connectivity in mouse visual thalamus and cortex

How neuronal activity is shaped by circuit connectivity between neuronal populations is a central question in visual neuroscience. Combined with experimental data, computational models allow causal investigation and prediction of both how connectivity influences activity and how activity constrains connectivity. In order to develop and refine these computational models of the visual system, thorough characterization of neuronal response patterns is required. In this thesis, I first present an approach to infer connectivity from in vivo stimulus responses in mouse visual cortex, revealing underlying principles of connectivity between excitatory and inhibitory neurons. Second, I investigate suppressed-by-contrast neurons, which, while known since the 1960s, still remain to be included in standard models of visual function. I present a characterization of intrinsic firing properties and stimulus responses that expands the knowledge about this obscure neuron type. Inferring the neuronal connectome from neural activity is a major objective of computational connectomics. Complementary to direct experimental investigation of connectivity, inference approaches combine simultaneous activity data of individual neurons with methods ranging from statistical considerations of similarity to large-scale simulations of neuronal networks. However, due to the mathematically ill-defined nature of inferring connectivity from in vivo activity, most approaches have to constrain the inference procedure using experimental findings that are not part of the neural activity data set at hand. Combining the stabilized-supralinear network model with response data from the visual thalamus and cortex of mice, my collaborators and I have found a way to infer connectivity from in vivo data alone. Leveraging a property of neural responses known as contrast-invariance of orientation tuning, our inference approach reveals a consistent order of connection strengths between cortical neuron populations as well as tuning differences between thalamic inputs and cortex. Throughout the history of visual neuroscience, neurons that respond to a visual stimulus with an increase in firing have been at the center of attention. A different response type that decreases its activity in response to visual stimuli, however, has been only sparsely investigated. Consequently, these suppressed-by-contrast neurons, while recently receiving renewed attention from researchers, have not been characterized in depth. Together with my collaborators, I have conducted a survey of SbC properties covering firing reliability, cortical location, and tuning to stimulus orientation. We find SbC neurons to fire less regularly than expected, be located in the lower parts of cortex, and show significant tuning to oriented gratings

Evaluation of reinforced cementitious seals

"The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory, cooperated with Tecrete Industries Pty. Ltd. and BHP Australia Coal in a research program to evaluate the strength characteristics and air leakage of four seal and two stopping designs for use in underground coal mines. A fundamental safety research area for NIOSH is to eliminate the occurrence of coal mine explosions or to mitigate their effects. One approach to achieve this goal is to develop new and innovative seal designs that provide increased explosion isolation protection for the mining personnel against ignitions that originate from within the gob or other worked-out areas of the mine. Full-scale seals and stoppings were constructed in the Experimental Mine at Lake Lynn Laboratory near Fairchance, Fayette County, PA. They were air-leakage tested, then subjected to a series of explosions with average pressure pulses ranging from 25 to 500 kPa (3.5 to 72 psi). Instrumentation measured seal displacement and acceleration as a function of time, providing data to assist in the development of numerical models for future seal design. All three seals designed with Meshblock wire formwork and a monolithic shotcrete core withstood the first explosion test, which generated an average maximum pressure of -140 kPa (-20 psi) while maintaining acceptable air leakage rates. These seals ranged from 175 to 325 mm thick. They included a 2.7-m-high by 325-mm-thick seal that was tested 27 hr after completion against this - 140-kPa explosion pressure, a special requirement of the test program. This seal survived explosions with pressure pulses up to 300 kPa (43 psi). The 2.3-m-high by 325-mm-thick Meshblock seal survived three explosion tests with overpressures up to 455 kPa (66 psi) and satisfied the air leakage criteria. A 1,200-mm-thick plug seal was constructed of two Gunmesh formwork walls in-filled with shotcrete and a 3,450-kPa (500-psi) strength Aquablend core. This plug seal survived three explosions with pressure pulses ranging from 150 to 430 kPa (-22 to 62.5 psi) with no measurable post explosion air leakage. Two Gunmesh stoppings with thicknesses of 40 and 75 mm withstood explosion overpressures of 23 and 115 kPa, respectively. Anchoring all seal and stopping designs into the roof, ribs, and floor with steel "roofbolts" provided very effective boundary constraint that is critical to the performance of structures subject to explosion overpressures." - NIOSHTIC-2by by Eric S. Weiss, Kenneth L. Cashdollar, I. Verne S. Motton, Deepak R. Kohli and William A. Slivensky.Also availalble via the World Wide Web.Includes bibliographical references

Measurements of stellar spectra using a silicon photodiode array

This work describes the preparation and use of the Plessey linear photodiode array in the observation of some stellar spectral features. An outline of the principles of the construction and operation of the diode array, along with some preliminary laboratory test results, form the initial part of this thesis. A suitable xy-movement control was designed and constructed, as well as the cryostat which was used to house the array at the coude focus of the telescope. Constraints at the telescope imposed several limitations, all of which had to be taken into consideration. The general experimental operation, signal processing, and control logic are all described, along with the data acquisition and storage techniques. Data reduction and analysis methods were developed to deal with difficulties peculiar to this type of photodiode array system. A theoretical investigation into the effects of the array geometry on the collection of spectra is described. On the astronomical side, observations of the neutral oxygen triplet at A7774 form the major set of results obtained. The equivalent width of A7774 can give information about the temperature absolute magnitude, and luminosity of many types of stars. The role of non-LTE is discussed, as well as its effect on the measurements of line widths. Finally, the phenomenon of stellar mass loss is outlined. Unfortunately, few results were obtained in this investigation. However, a description of the reasons behind the loss of matter from stars is given, along with probable mass loss mechanisms, features, and detection. A brief word on mass loss rates is included, but the lack of sufficient results in this region pre-empted any quantitative comparisons

Changing the functionality of cocoa butter

Cocoa butter is an essential ingredient in chocolate as it forms the continuous phase of chocolate. It’s therefore responsible for the gloss, texture and typical melting behaviour of ‘irresistible’ chocolate. The aim of this research was to change the functionality of cocoa butter by two different methods. In the first part, cocoa butter was modified by physical refining by using packed column steam refining with or without silica pretreatment. The physicochemical properties of the refined cocoa butters were determined and in the next step they were applied in a milk chocolate formulation. The produced milk chocolates were then evaluated for different quality characteristics. It was clear that the free fatty acids played a predominant role but the exact mechanism remained unclear. In the second part of this research, cocoa butter was changed more drastically as it was submitted to an enzymatic modification process, aiming to produce diacylglycerols. Diacylglycerols have distinct physicochemical properties compared to triacylglycerols due to the presence of a free hydroxyl group. An enzymatic glycerolysis reaction was optimized and a highly purified diacylglycerol fraction was obtained by short path distillation. The produced diacylglycerols were physicochemically characterized and blended with cocoa butter to screen their applicability in confectionary products. A multi-methodological approach was used to study the isothermal crystallization of cocoa butter at 20°C. In the last part of the research, the cocoa butter based diacylglycerols were applied in a dark chocolate formulation and the functional properties were derived by determining the melting and rheological behaviour and texture. As migration fat bloom remains one of the major quality issues in composed chocolate products, it was investigated whether cocoa butter based diacylglycerols could delay or prevent this phenomenon

Impacts of feeding peroxidized oils on growth and oxidative status in swine and poultry

It is common for vegetable oils to be supplemented to livestock diets to improve the energy density of the feed. Vegetable oils, however, have high concentrations of polyunsaturated fatty acids (PUFA). Due to this increased unsaturation, they are predisposed to lipid damage through lipid peroxidation. Lipid peroxidation is a dynamic free radical chain reaction that can be initiated by thermal processing in the presence of oxygen. This reaction progresses based on duration and intensity of thermal processing to produce a wide range of potentially oxidative and toxic compounds. Lipid peroxidation products of interest include peroxide value (PV) which measures hydroperoxides formed, and p-anisidine value (AnV) which is a measure of the molecular weight of aldehydes. Two key aldehydes are also formed including 2,4-decadienal (DDE) and 4-hydroxynonenal (HNE), are formed from the peroxidation of linoleic acid and are of interest because of their reactiveness with lipids, proteins, and DNA. Oils from ethanol, rendering or the restaurant industries may be an economical energy source compared to fresh oil, but at the expense of oil quality as they may be thermally peroxidized. Consumption of these peroxidized oils may induce increased oxidative stress and antagonize livestock performance. Oxidative stress occurs in the event that oxidative compounds such as free radicals and reactive oxygen species (ROS) overwhelm the antioxidant defense system. Enzymatic antioxidants including superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) function in detoxifying (reducing) oxidative compounds to protect the body from oxidative stress. Oxidative compounds can bind to lipids, proteins, and DNA to stabilize resulting in tissue or cellular damage. Commonly, thiobarbituric acid reactive substances (TBARS) and F2-isoprostanes (ISP) are measured as indicators of lipid damage, protein carbonyls (PC) are measured as an indicator of protein damage, and 8-hydroxy-2\u27-deoxyguanosine (8-OH-2dG) is measured as an indicator of DNA damage. However, there is a poor understanding of the effects of feeding peroxidized oils on growth performance, digestibility, and oxidative status in livestock. Therefore, the overall objectives of this thesis were to determine the impact of feeding peroxidized oils on growth and digestibility parameters, and whole body oxidative status in growing pigs and poultry. To accomplish these objectives, a series of experiments were conducted and are outlined in three chapters (Chapter 2, 3, and 4). In Chapter 2, an experiment was conducted feeding variable levels of peroxidized soybean oil (SO) on growth, digestibility, and intestinal integrity parameters in growing pigs. In Chapter 3 oxidative stress markers associated with lipid, protein, and DNA damage along with enzymatic antioxidants, were measured in pigs fed variable levels of dietary peroxidized soybean oil. The final chapter (Chapter 4) assessed the effects of feeding multiple fresh and peroxidized oil sources on growth performance and markers of oxidative stress in broilers. The data herein indicate that thermally processing oils at 90oC for 72 h yielded the most harmful lipid peroxidation products as exhibited by reduced overall growth performance and feed efficiency in swine and poultry. Pigs fed thermally peroxidized SO (heated at 90oC for 72 h, 90oC SO) had reduced ADG, energy and lipid digestibility, and whole body N retention (Chapter 2). Further, these pigs also had increases in liver weight as a percentage of BW and generally had increased oxidative stress as measured by serum PC and GPx, urine ISP, and liver 8-OH-2dG (Chapter 3). To build on Chapters 2 and 3, Chapter 4 evaluated the effects of feeding fresh and peroxidized palm, soybean, flaxseed, and fish oils on performance and oxidative status in poultry. An interaction between oil source and peroxidation status was noted for ADFI, ADG, G:F, and plasma GPx in broilers where peroxidation status reduced each of these variables in birds fed palm, soybean, and flaxseed oil, apart from birds fed fish oil. In general, oil unsaturation increased plasma TBARS, PC and 8-OH-2dG; furthermore, broilers fed peroxidized oils had increased plasma 8-OH-2dG. An interaction was noted in liver TBARS where broilers fed peroxidized palm oil had increased liver TBARS compared to fresh palm oil, while the opposite was true in broilers fed soybean oil, and no change was noted in broilers fed flaxseed oil and fish oil. An interaction was also noted for liver PC where broilers fed palm, flaxseed, and fish oil had similar liver PC regardless of peroxidation status while broilers fed peroxidized soybean oil had increased liver PC compared to the fresh soybean oil diet. Generally speaking, the unsaturation content of the dietary oil increased liver 8-OH-2dG and CAT activity and peroxidation status increased liver SOD activity. In summary, this thesis reported that formulating diets for pigs and poultry containing thermally processed oils (5-10% of total diet) were shown to have detrimental effects on performance particularly ADG. In pigs, thermally peroxidized SO also reduced digestibility of energy, ether extract, and nitrogen retention in comparison to pigs fed fresh SO. Additionally, growth performance was decreased in poultry fed peroxidized palm, soybean, and flaxseed oils. Oxidative stress was induced in swine and poultry fed peroxidized oils and different oil sources as measured in urine (pigs only), blood, and liver. Further, this data suggests that PV, DDE or AnV, PTAGS, and total tocopherols are important lipid peroxidation products that need to be measured as suggested by their consistent correlations with growth performance and oxidative status in swine and poultry. Additionally, these experiments and a review of literature indicate that markers of oxidative stress that should be measured include ISP and 8-OH-2dG in urine (pigs), and PC and GPx in blood (pigs and poultry). Overall, this thesis showed that oil quality should not be underestimated in livestock production. Feeding peroxidized oils can induce oxidative stress and antagonizes growth performance and digestibility in swine and poultry