An electronic system was designed to receive a signal from a Self Powered Neutron Detector (SPND) and measure the initial period (e-folding time) of the TRIGA reactor at the University of Arizona. The design and fabrication of the SPND used was part of this work. The electronic system together with the SPND were used to construct a reactivity worth calibration curve for the transient rod based on pulse measurements.

A dose rate measurement survey was performed at various locations inside the radiation chamber of the Cobalt-60 gamma irradiation facility located in Room 130, Building 20 at the University of Arizona. TLDs were used for the dose rate measurements. It was observed that the dose rates decrease rapidly with increasing distance from the source. Also, dose rates decreased with increased distance away from the centerline of the radiation chamber which is indicative of the position of the effective center of the source. Percent dose rates with respect to the dose rate of the calibration position were tabulated.

Charged particle beam source problems are difficult to simulate because of the extremely large and anisotropic scattering cross sections, and the associated singularities in angle and space. To overcome these difficulties the Extended First Collision Source method and the SMART (Simulation of Many Accumulative Rutherford Trajectories) scattering method have been developed. In this study, the extended first collision source calculation was improved in the SN code using the SMART scattering method which produces smoother and smaller effective cross sections. To determine the uncollided flux which was necessary for the first collision source calculation, the SMART scattering cross sections were used instead of screened Rutherford scattering cross sections. After the SN code was modified, it produced results that approached those obtained using the benchmark Monte Carlo code.

<p> In inertial confinement fusion (ICF), the kinetic ion and charge separation field effects may play a significant role in the difference between the measured neutron yield in experiments and the predicted yield from fluid codes. Two distinct of approaches exists in modeling plasma physics phenomena: fluid and kinetic approaches. While the fluid approach is computationally less expensive, robust closures are difficult to obtain for a wide separation in temperature and density. While the kinetic approach is a closed system, it resolves the full 6D phase space and classic explicit numerical schemes restrict both the spatial and time-step size to a point where the method becomes intractable. Classic implicit system require the storage and inversion of a very large linear system which also becomes intractable. This dissertation will develop a new implicit method based on an emerging moment-based accelerator which allows one to step over stiff kinetic time-scales. The new method converges the solution per time-step stably and efficiently compared to a standard Picard iteration. This new algorithm will be used to investigate mixing in Omega ICF fuel-pusher interface at early time of the implosion process, fully kinetically. </p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3760. Adviser: Roy Axford. Includes supplementary digital materials. Includes bibliographical references (leaves 260-263) Available on microfilm from Pro Quest Information and Learning.

Thesis (M.S.)--Lehigh University, 2009. / Adviser: Eugenio Schuster.

A multi-region, transient concrete ablation and decomposition model is developed. The model consists of four regions of concrete containing a thermally affected region, a dry (evaporated and chemically dehydrated) region, and a gas-free (decarboxylated) region with ablated concrete at the melt/concrete interface. Each region has an interface where the latent heat of local decomposition reactions is taken into account as heat sinks due to endothermic characteristics of the reactions. The time dependent temperature profiles, and depth and growth rate of the regions are evaluated by use of the heat balance integral method. Solutions are obtained for surface heat fluxes in forms of constant, e ⁻(λ)ᵗ, t⁻(λ) and -At to analyze various melt cooldown schemes. The erosion front progresses with a constant rate proportional to the surface heat flux in case of constant heat flux, and terminates at a finite erosion depth that is logarithmically proportional to the cooldown rate for surface heat flux in forms of ⁻(λ)ᵗ and t⁻(λ). Sensitivity analyses are performed to investigate the effects of important thermophysical parameters. Larger erosion depth and rate is observed for higher thermal conductivity. Decomposition temperatures are found to be significant in ablation. Model results were compared with previous experiments and models, and determined to be valid and accurate for different types of melt/concrete interaction. The model presented in this study is simple yet very detailed and accurate in simulating the actual molten core/concrete interaction (MCCI) phenomena, and in investigating the concrete reaction to the molten core. It not only can be embodied into the MCCI codes currently being developed, but also can be used to determine the containment integrity, and fission products released into the environment and to the public as a stand alone code.

A textbook which merges nuclear engineering theory and principle with central station nuclear power plant application was developed and implemented. Palo Verde Nuclear Generating Station operating processes and procedures were used as the arena within which to develop and apply nuclear, thermodynamic, and fluid dynamic theoretical principles. From plant heatup, through nuclear startup and power ascension, to power operation and then to plant shutdown, nuclear engineering principles are applied through the use of discussions, examples, problems and study questions. Detailed descriptions and solutions are included. Used as the text for a senior level course at U of A Nuclear Engineering Department in Spring 1993 and for engineer training at Palo Verde in January, 1994, this text has been developed, evaluated, tested and revised to assure applicability and thoroughness. The resultant instrument has been adopted as the text for required initial training of Shift Technical Advisors at Palo Verde Nuclear Generating Station.

The first objective of this study was to determine and compare the fatigue damage from two different vibration events versus the fatigue damage from an envelope of both events. The second objective was to determine and compare the fatigue damage from the equipment test versus the fatigue damage from a section test while using the same vibration envelope. Both objectives were accomplished using NASTRAN models to calculate internal loads for use in the fatigue analysis. This study proved that the vibration envelope produced three times more fatigue damage than the worst vibration event, and two times more fatigue damage than both events applied sequentially. When the same vibration envelope was used in an equipment test and a section test, the analytical results showed the internal loads were quite different. Furthermore, this study demonstrated the need to validate and update analytical models with actual test data to derive accurate equipment loads.

<p> The following work describes investigations of spatial dosimetry using laser-induced fluorescence of a radio-fluorogenic detector embedded within water-equivalent media. The chemical composition of a gelatin-based coumarin-3-carboxylic acid detector was investigated and dose response characterized. Violet diode (405nm) excitation sources were explored and laser-induced fluorescence (LIF) employed to obtain the pattern of fluorescent emission yielding images of the integrated spatial dose distribution. The design of a three-dimensional reader is proposed to provide a foundation for future work. </p><p> Radio-fluorogenic processes create fluorescent products in response to ionizing radiation. Water radiolysis produced by ionizing radiation yields hydroxyl free radicals that readily hydroxylate coumarin-3-carboxylic acid to 7-hydroxy-coumarin-3-carboxylic acid, a derivative of umbelliferone. Umbelliferone is a known fluorophore, exhibiting peak excitation in the UV to near UV range of 365-405nm with a visible 445nm blue emission. Coumarin-3-carboxlyic acid has been studied in an aqueous gelatin matrix. </p><p> The radio-fluorogenic coumarin-gelatin detector has been shown to respond to an absorbed dose of ionizing radiation in a measureable manner. The detector was studied with respect to concentration of gelatin and coumarin in the presence of pH buffers. Dose response of the detector was investigated with regard to ionizing radiation type, energy, and rate of irradiation. Results demonstrate a functional detector. </p><p> Patterns of energy deposition were formed in response to ionizing radiation produced by a sealed-source of radioactive Ir-192 embedded in the gelatin matrix of the detector. Spatial distributions of absorbed dose were recorded and analyzed as a function of fluorescent emission. The distribution of energy deposition was imaged with LIF excitation by a divergent beam of 405nm light and determined by analysis of digital image pixel intensity values displaying the 445nm fluorescent emission. Results demonstrate spatial dosimetry proof of principle. </p><p> A basic dedicated reader system was fabricated employing LIF. Images of fluorescent emission excitation profiles were obtained in multiple aqueous samples and processed to obtain a dose response. Design of an optical reader system for the radio-fluorogenic detector is explained and a three-dimensional dosimetry system proposed. Three-dimensional imaging principles with LIF have been illuminated.</p>