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Navarro J.,Center for Space Nuclear Research | Ring T.A.,University of Utah | Nigg D.W.,Idaho National Laboratory
Nuclear Technology | Year: 2015

A deconvolution methodology aimed to reduce the uncertainty for nondestructively predicting fuel burnup using gamma spectra collected with LaBr3 scintillators was developed. Deconvolution techniques have been used in the past to improve photopeak resolution of data collected using gamma detectors; however, they have not been used as a tool to more accurately predict fuel burnup. The deconvolution methodology consisted of calculating the detector response function using Monte Carlo simulations, validating the detector response function against experimental data, and implementing the maximum likelihood expectation maximization algorithm to enhance the LaBr3 gamma spectra. The deconvolution methodology was first tested on singleisotopic simulated data; later it was applied to fuel simulated data that were based on Advanced Test Reactor (ATR) fuel gamma spectra. The study showed that LaBr3 gamma spectra photopeak resolution and quality can be improved significantly using deconvolution methods, in addition to proving that enhancement techniques can be used to nondestructively predict ATR fuel burnup more accurately than using LaBr3 data without enhancements. Source

Crawford D.S.,Center for Space Nuclear Research | Ring T.A.,University of Utah
Annals of Nuclear Energy | Year: 2012

Normalized neutron energy moments (moments) from the one-dimensional energy dependent neutron diffusion equation (EDNDE), Monte Carlo N Particle 5 version 1.40 (MCNP5) and Attila-7.1.0-beta version (Attila) are validated with the GODIVA experiment (GODIVA). Energy moments 0-5 for all three methods are compared to GODIVA moments. GODIVA moments are measured with two methods. The 1st method is a time of flight (T-O-F) measurement of the average energy (moment 1) of the leaking neutrons from the surface of GODIVA and the 2nd method is from back calculating moments from foil activation analysis of various metal foils at the center of GODIVA. The error range of the EDNDE normalized moments compared to GODIVA is from 0% to 24%. The MCNP5 error range compared to GODIVA is 0-12% and the Attila error range is 0-79%. The method of moments is shown to be a fast reliable method, compared to either Monte Carlo methods (MCNP5) or 30 multi-energy group methods (Attila) with regard to the GODIVA experiment. © 2012 Elsevier Ltd. All rights reserved. Source

Liao C.,Abs Consulting | Best F.R.,Texas A&M University | Best F.R.,Center for Space Nuclear Research
Journal of Thermophysics and Heat Transfer | Year: 2010

Acomprehensive one-dimensional analytical model has been developed for gas ejector design and analysis. Unlike existing models, no assumptions have been made to simplify the momentum conservation equation for the ejector mixing chamber (that is, constant-pressure and constant-area models). Instead, the new model solves the momentum equation, which results in improved accuracy and versatility over existing models. Previous models can be derived from the new model as particular cases. These derivations provide new understanding of the relationships between the constant-pressure and constant-area one-dimensional ejector analytical models. The new model extends to the problems left unsolved by existing models and is efficient in analyzing off-design operating conditions, such as the shock that occurs in the primary stream. From the new model, the limitations on ejector design and operation are also recognized. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source

Zhang X.,Idaho National Laboratory | O'Brien J.E.,Idaho National Laboratory | O'Brien R.C.,Center for Space Nuclear Research | Housley G.K.,Idaho National Laboratory
Journal of Power Sources | Year: 2013

An experimental investigation on the performance and durability of single solid oxide cells (SOCs) is under way at the Idaho National Laboratory. Reversible operation of SOCs includes electricity generation in the fuel cell mode and hydrogen generation in the electrolysis mode. Degradation is a more significant issue when operating SOCs in the electrolysis mode. In order to understand and mitigate the degradation issues in high temperature electrolysis, single SOCs with different configurations from several manufacturers have been evaluated for initial performance and long-term durability. Cells were obtained from four industrial partners. Cells from Ceramatec Inc. and Materials and Systems Research Inc. (MSRI) showed improved durability in electrolysis mode compared to previous stack tests. Cells from Saint Gobain Advanced Materials Inc. (St. Gobain) and SOFCPower Inc. demonstrated stable performance in the fuel cell mode, but rapid degradation in the electrolysis mode, especially at high current density. Electrolyte-electrode delamination was found to have a significant impact on degradation in some cases. Enhanced bonding between electrolyte and electrode and modification of the electrode microstructure helped to mitigate degradation. Polarization scans and AC impedance measurements were performed during the tests to characterize cell performance and degradation. © 2013 Elsevier B.V. All rights reserved. Source

Howe S.D.,Center for Space Nuclear Research
Nuclear and Emerging Technologies for Space 2011, NETS-2011 | Year: 2011

With an increasing demand for long-duration and energy intensive missions in space, alternatives to radioisotope power systems are being explored. Nuclear fission reactors can provide sufficient power while maintaining a low specific mass comparable to radioisotope power systems. One of the projects focused on designing a small scale nuclear reactor with a low specific mass for use on a fourteen year unmanned mission. The results show a craft can be made that requires no internal pumps or electrical input to run the power conversion system. The power conversion system selected consisted of free-piston Stirling engines. The core design is based upon a heat pipe thermal transport system using a U10Mo Core, while a liquid bath controls thermal conditions around the power conversion systems. The radiators are also designed with carbon composite materials. Results of this paper show a reduction in specific mass of the system. Source

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