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Articles 1 - 5 of 5
Full-Text Articles in Nuclear Engineering
A Two-Dimensional Spherical-Polar Multigroup Discrete Ordinates Code For Atmospheric Particle Transport, Daniel T. Wakeford
A Two-Dimensional Spherical-Polar Multigroup Discrete Ordinates Code For Atmospheric Particle Transport, Daniel T. Wakeford
Nuclear Engineering ETDs
A natural coordinate system for calculating neutral particle propagation in the atmosphere due to point sources is two-dimensional spherical-polar coordinates. Deterministic methods for solving the transport equation in this coordinate system require some interesting implementation details stemming from the two angular derivatives present in this form of the equation. In this dissertation, we present a bilinear discontinuous spatial discretization of the transport equation in this coordinate system. The weighted diamond difference discretization is applied to the angular derivative term in two angular dimensions, using zero-weighted starting directions to start the differencing. To our knowledge, the only previous deterministic code that …
Characterization Of Partial Charge Collection Induced By Neutron Damage In High-Purity Germanium Detectors, James W. Evans
Characterization Of Partial Charge Collection Induced By Neutron Damage In High-Purity Germanium Detectors, James W. Evans
Nuclear Engineering ETDs
This paper investigates the correlation of damage induced by neutron interactions and degradation in the spectra of HPGe detectors. As neutrons kinetically interact with germanium crystals, they create interstitial and vacancy defects within the lattice. These defects then interfere with the charge migration of electron-hole pairs and reduce resolution in the observed energy spectrum. The partial charge collection produces observable spectral changes by increasing the peak width and reducing resolution (full width half maximum). A detailed characterization using various check sources was performed before and after iterations of neutron exposure in order to observe the effects of the neutron damage. …
A Forward Analytic Model Of Neutron Time-Of-Flight Signals With Single Elastic Scattering And Beamline Attenuation For Inferring Ion Temperatures From Maglif Experiments, Colin A. Weaver
Nuclear Engineering ETDs
A forward analytic model is required to rapidly simulate the neutron time-of-flight (nToF) signals that result from magnetized liner inertial fusion (MagLIF) experiments at Sandia’s Z Pulsed Power Facility. Various experimental parameters, such as the burn-weighted fuel-ion temperature and liner areal density, determine the shape of the nToF signal and are important for characterizing any given MagLIF experiment. Extracting these parameters from measured nToF signals requires an appropriate analytic model that includes the primary DD neutron peak, once-scattered neutrons in the beryllium liner of the MagLIF target, and direct beamline attenuation. Mathematical expressions for this model were derived from the …
Modeling And Simulation Of Stochastic Neutron And Cumulative Deposited Fission Energy Distributions, Patrick O'Rourke
Modeling And Simulation Of Stochastic Neutron And Cumulative Deposited Fission Energy Distributions, Patrick O'Rourke
Nuclear Engineering ETDs
Methods of stochastic neutron transport are investigated and applied to novel formulations for the neutron number distribution and the cumulative fission energy deposition distribution. We utilize two Monte Carlo algorithms: the event-based Monte Carlo (EBMC) method and the Stochastic Simulation Algorithm (SSA) to benchmark and analyze systems. We show that the SSA outperforms the EBMC for the parameter space we are interested in. We then utilize the SSA to analyze systems composed of multiple spherical regions with fast and thermal neutrons with time-dependent reactivity insertions and determine whether group-dependent number distributions approach a gamma distribution. We develop two methods for …
Characterization Of Uranium Foil Irradiations At The Wsu Triga Reactor Using A New Reactor Model In Scale, Kimberly A. Hinrichs
Characterization Of Uranium Foil Irradiations At The Wsu Triga Reactor Using A New Reactor Model In Scale, Kimberly A. Hinrichs
Nuclear Engineering ETDs
A new reactor model of the Washington State University TRIGA was developed in the SCALE neutron transport code, and its fidelity was verified by comparison to MCNP and available data for several reactor parameters. The model was used to characterize irradiations designed to produce the short-lived actinides 237U and 239U, two key isotopes for nuclear forensics. These short-lived actinides, their decay daughters 237Np and 239Pu, and total fissions (via 99Mo) were measured in irradiated foils at Los Alamos National Laboratory and other labs with good agreement among parent/daughter pairs and among labs. The laboratory-measured isotope …