http://hdl.handle.net/1957/31642 2013-05-25T03:27:50Z 2013-05-25T03:27:50Z Farsoni, A. T. Alemayehu, B. Alhawsawi, A. Becker, E. M. http://hdl.handle.net/1957/37995 2013-04-03T20:29:54Z 2013-02-01T00:00:00Z

A Phoswich Detector with Compton Suppression Capability for Radioxenon Measurements Farsoni, A. T.; Alemayehu, B.; Alhawsawi, A.; Becker, E. M. A phoswich detector with Compton suppression capability has been developed and tested for measuring xenon radioisotopes via a beta-gamma coincidence measurement technique. The phoswich detector has been designed with three scintillation layers. Beta-gamma coincidence events from radioxenon isotopes are identified when a coincidence energy absorption is detected in the first (BC-400) and second (CsI(Tl) crystal) scintillation layers. To identify and reject scattered photons from the CsI(Tl) crystal, the crystal is surrounded by a BGO scintillation layer. Our measurements show that the Compton suppression mechanism reduces the Compton continuum from 662 keV photons by 20%-50% in the low-energy region of spectrum. Our beta-gamma coincidence measurements with ¹³⁵Xe and ¹³³Xe radioisotopes show energy resolutions (FWHM) of 13%, 46% and 24% for 250 keV, 30keV and 80 keV gamma-ray peaks, respectively. In this paper, the detector design, assembly steps, digital pulse shape discrimination technique, and our recent measurements with radioactive lab sources and xenon radioisotopes are discussed. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by IEEE-Institute of Electrical and Electronics Engineers and can be found at: http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=23. (c) 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

2013-02-01T00:00:00Z Makinson, K. A. Hamby, D. M. Edwards, J. A. http://hdl.handle.net/1957/37974 2013-04-03T00:06:35Z 2012-12-01T00:00:00Z

A Review of Contemporary Methods for the Presentation of Scientific Uncertainty Makinson, K. A.; Hamby, D. M.; Edwards, J. A. Graphical methods for displaying uncertainty are often the most concise and informative way to communicate abstract concepts. Presentation methods currently in use for the display and interpretation of scientific uncertainty are reviewed. Numerous subjective and objective uncertainty display methods are presented, including qualitative assessments, node and arrow diagrams, standard statistical methods, box-and-whisker plots, robustness and opportunity functions, contribution indexes, probability density functions, cumulative distribution functions, and graphical likelihood functions. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Health Physics Society and published by Lippincott Williams & Wilkins. The published article can be found at: http://journals.lww.com/health-physics/pages/default.aspx.

2012-12-01T00:00:00Z Caffrey, J. A. Higley, K. A. Farsoni, A. T. Smith, S. Menn, S. http://hdl.handle.net/1957/37055 2013-02-20T19:53:07Z 2012-09-01T00:00:00Z

Development and deployment of an underway radioactive cesium monitor off the Japanese coast near Fukushima Dai'ichi Caffrey, J. A.; Higley, K. A.; Farsoni, A. T.; Smith, S.; Menn, S. A custom radiation monitoring system was developed by Oregon State University at the request of the Woods Hole Oceanographic Institute to measure radioactive cesium contaminants in the ocean waters near Fukushima Dai’ichi Nuclear Power Plant. The system was to be used on board the R/V Ka’imikai-O-Kanaloa during a 15 d research cruise to provide real-time approximations of radionuclide concentration and alert researchers to the possible occurrence of highly elevated radionuclide concentrations. A NaI(Tl) scintillation detector was coupled to a custom-built compact digital spectroscopy system and suspended within a sealed tank of continuously flowing seawater. A series of counts were acquired within an energy region corresponding to the main photopeak of ¹³⁷Cs. The system was calibrated using known quantities of radioactive ¹³⁴Cs and ¹³⁷Cs in a ratio equating to that present at the reactors’ ocean outlet. The response between net count rate and concentration of ¹³⁷Cs was then used to generate temporal and geographic plots of ¹³⁷Cs concentration throughout the research cruise in Japanese coastal waters. The concentration of ¹³⁷Cs was low but detectable, reaching a peak of 3.8 ± 0.2 Bq/L. This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/journal-of-environmental-radioactivity/.

2012-09-01T00:00:00Z Sabharwall, Piyush Yoo, Yeon Jong Wu, Qiao Sienicki, James J. http://hdl.handle.net/1957/36610 2013-02-06T21:13:25Z 2012-06-01T00:00:00Z

Natural Circulation and Linear Stability Analysis for Liquid-Metal Reactors with the Effect of Fluid Axial Conduction Sabharwall, Piyush; Yoo, Yeon Jong; Wu, Qiao; Sienicki, James J. The effect of fluid axial thermal conduction on one-dimensional liquid metal natural circulation and its linear stability was performed through nondimensional analysis, steady-state assessment, and linear perturbation evaluation. The Nyquist criterion and a root-search method were employed to find the linear stability boundary of both forward and backward circulations. The study provided a relatively complete analysis method for one-dimensional natural circulation problems with the consideration of fluid axial heat conduction. The results suggest that fluid axial heat conduction in a natural circulation loop should be considered only when the modified Peclet number is similar to 1 or less, which is significantly smaller than the practical value of a lead liquid metal cooled reactor. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by American Nuclear Society and can be found at: http://www.new.ans.org/pubs/journals/nt/.

2012-06-01T00:00:00Z