NE Seminar: “A New Approach to Mitigating Ray Effects in Discrete Ordinates Solutions to Radiation Detection Problems”

Date(s) - 10/21/2021
1:55 pm - 2:55 pm

Rhines 125


Yousry Azmy, Ph.D.

Duke Energy Distinguished Professor
Department of Nuclear Energy
North Carolina State University

Dr. Yousry Azmy received his Ph.D. in Nuclear Engineering from the University of Illinois at Urbana-Champaign, in 1985. Upon graduating, he took a one-year position as Research Assistant Professor in the Nuclear Engineering and Engineering Physics Department at the University of Virginia, Charlottesville. In 1986 he joined the research staff of the Computational Physics and Engineering Division of Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee. Over the following sixteen years, he ascended the ranks of the research ladder while focusing his research on issues in nuclear computational science, particularly on aspects of the numerical solution of the neutron transport equation. These include advanced numerical methods, numerical error estimation and analysis, iterative acceleration schemes, and parallel solution algorithms. In July 2002 he resigned from his Senior Scientist position at ORNL to become Professor of Nuclear Engineering in the Department of Mechanical and Nuclear Engineering at Penn State University, University Park. Starting June 1, 2008, Dr. Azmy was appointed Professor and Head of the Department of Nuclear Engineering at North Carolina State University, Raleigh. Dr. Azmy is a member of the American Nuclear Society (since 1985), SIAM (since 2000), the American Mathematical Society (since 2001), and the American Society for Engineering Education (since 2005). He was elected Fellow of the American Nuclear Society (ANS) in 2002 and has won the ANS’ 1995 Young Member Engineering Achievement Award, as well as the ANS Mark Mills Award in 1986, among other honors and awards. He is professionally active in the ANS serving on its Board of Directors, 2013-16, and has previously chaired the Technical Journals Committee, 2011-14, and the Nuclear Engineering Department Heads Organization (NEDHO), 2011-12, among several other services to the society over the past 36 years. Since 1995, he has been a member of the Organization for Economic Cooperation and Development’s (OECD) Nuclear Energy Agency (NEA) Experts Group on Three Dimensional Transport Methods and Codes. In May 2012 Dr. Azmy was elected to a three-year term on the Board of Directors of the Nuclear Energy Institute. From 2014 till 2020 Dr. Azmy served as the Director of the Consortium for Nonproliferation Enabling Capabilities (CNEC), a five-year, $5M per year, seven university plus four national laboratory collaborations sponsored by the US National Nuclear Security Administration (NNSA). In January 2015 he was named Editor of the international journal Progress in Nuclear Energy, and in January 2016 he was appointed NCSU representative to the National University Consortium (NUC) that partners in the management of the Idaho National Laboratory for the US DOE. In June 2015 he relinquished his Department Head position to focus his efforts on these added responsibilities. In recognition of his career accomplishments and service to NC State University, he was named Distinguished Professor in the Department of Nuclear Engineering in 2016, then in 2018, he was named Duke Energy Distinguished Professor of Nuclear Engineering. Over his career, Dr. Azmy served as a consultant to a wide variety of domestic and international, academic and governmental organizations.



The method of Discrete Ordinates (SN) used to discretize angular dependence of the transport equation provides a computationally efficient means to its numerical solution. Nevertheless, in certain configurations, primarily highly localized sources in weakly scattering media, the resulting SN solutions suffer ray effects manifested as non-physical spatial oscillations of the scalar flux. These effects render the SN solution inaccurate, especially far from the localized source where, for example, a radiation detector may be placed relative to the radioactive material it is supposed to measure. After reviewing the traditional approach based on a ray-tracing pre-process to compute the uncollided flux and first collision source and its deficiencies, we propose a new approach based on pre-computing the n-collided flux and (n+1)-collision source using Monte Carlo simulations. We use a simple test configuration to establish proof-of-principle, then we use a realistic radiation detection configuration to verify the mitigation of ray effects in such applications.