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Efficient Multiphysics Coupling For Fast Burst Reactors In Slab Geometry, Japan Patel
Efficient Multiphysics Coupling For Fast Burst Reactors In Slab Geometry, Japan Patel
Nuclear Engineering ETDs
In this thesis, we discuss a coupling algorithm to model simplified fast burst reactor dynamics. Kadioglu presented a tightly coupled multiphysics algorithm of diffusion neutronics and linear. An implicit-explicit (IMEX) algorithm was used to follow the dynamical time-scale of the problem. However, as noted by him and his co-authors, the diffusion model does not adequately represent the neutronics of the system due to its small. Our objective is to extend the IMEX algorithm to incorporate transport effects using moment based acceleration concept. We will demonstrate the differences between diffusion and transport models (SN). We will also demonstrate how the introduction …
An Sn Application Of Homotopy Continuation In Neutral Particle Transport, Nicholas Myers
An Sn Application Of Homotopy Continuation In Neutral Particle Transport, Nicholas Myers
Nuclear Engineering ETDs
The objective of this dissertation is to investigate the usefulness of homotopy continuation applied in the context of neutral particle transport where traditional methods of acceleration degrade. This occurs in higher dimensional heterogeneous problems [51]. We focus on utilizing homotopy continuation as a means of providing a better initial guess for difficult problems. We investigate various homotopy formulations for two primary diffcult problems: a thick-diffusive fixed internal source, and a k-eigenvalue problem with high dominance ratio. We also investigate the usefulness of homotopy continuation for computationally intensive problems with 30-energy groups. We find that homotopy continuation exhibits usefulness in specific …
Radiation Damage In Permanent Magnet Lenses, Christopher Danly
Radiation Damage In Permanent Magnet Lenses, Christopher Danly
Nuclear Engineering ETDs
Proton radiography techniques in use at Los Alamos National Lab and elsewhere depend upon permanent magnet quadrupoles in their magnetic optics. Radiation exposure during radiography experiments is known to damage these lenses and degrade image quality. This effect is studied under controlled conditions, leading to the conclusion that nonuniform radiation damage is inherent to the quadrupole configuration and results in increased multipole moments which degrade the imaging performance. Studies on magnet samples suggest that Samarium Cobalt is at least a thousand times more radiation-tolerant and should be used as a replacement for NdFeB in magnetic lenses for high-dose proton radiography.
Facility-Specific Radiation Exposure Risks And Their Implications For Radiation Workers At Department Of Energy Laboratories, Adam Davis
Nuclear Engineering ETDs
This research develops a new framework for evaluating the occupational risks of exposure to hazardous substances in any setting where As Low As Reasonably Achievable (ALARA) practices are mandated or used. The evaluation is performed by developing a hypothesis-test-based procedure for evaluating the homogeneity of various epidemiological cohorts, and thus the appropriateness of the application of aggregate data-pooling techniques to those cohorts. A statistical methodology is then developed as an alternative to aggregate pooling for situations in which individual cohorts show heterogeneity between them and are thus unsuitable for pooled analysis. These methods are then applied to estimate the all-cancer …
Moment-Based Accelerators For Kinetic Problems With Application To Inertial Confinement Fusion, William Taitano
Moment-Based Accelerators For Kinetic Problems With Application To Inertial Confinement Fusion, William Taitano
Nuclear Engineering ETDs
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 …
A Technique For Measuring The Time Response And Through-Put Delay Of Neutron Time-Of-Flight (Ntof) Scintillation Detectors Using Cosmic Radiation In A Coincidence System, Michael Bonura
Nuclear Engineering ETDs
Plastic scintillator-based neutron time-of-flight (nTOF) detectors are used to measure neutron signals from fusion experiments. These nTOF signals yield a temporal pulse width that is used to determine ion temperatures after the de-convolution of the experimentally determined detector time response and shifted to account for the detector through-put delay. Typically, time response and through-put delays are measured at an accelerator or laser facility. However, an alternative method can use cosmic radiation to measure time response and through-put delay. Two plastic scintillator detectors in a coincidence system can detect an incident cosmic ray. If a third nTOF detector is placed between …
Examining Thin Film Alsb For Room Temperature Gamma Detectors, Erin Vaughan
Examining Thin Film Alsb For Room Temperature Gamma Detectors, Erin Vaughan
Nuclear Engineering ETDs
A thin film semiconductor device was grown by MBE methods, characterized for material quality and evaluated for suitability as a room temperature gamma radiation detector. The objective was to produce a device that was superior to current semiconductor detectors, namely HPGe and CZT which have different limitations due to intrinsic material characteristics. AlSb was chosen because of its desirable properties which include the high atomic number of antimony (Z = 51), relatively large band gap (Eg = 1.6 eV), and theorized high dual carrier mobility. Simulations were performed using MCNP5 to predict energy deposited in AlSb by low energy gammas …
Simulations Of Space Radiation Interactions With Materials, With Application To Dose Estimates For Lunar Shelter And Aboard The International Space Station, Tai Pham
Nuclear Engineering ETDs
This research performed simulations using the state-of-art three dimensional computer codes to investigate the interactions of space radiation with materials and quantify the biological dose onboard the International Space Station (ISS) and in a lunar shelter for future manned missions. High-energy space radiation of Trapped Protons, Solar Particle Events, and GCRs particles interactions are simulated using MCNPX and PHITS probabilistic codes. The energy loss and energy deposition within the shielding materials and in a phantom are calculated. The contributions of secondary particles produced by spallation reactions are identified. Recent experimental measurements of absorbed dose in a phantom aboard the International …