Dr. Ayman I. Hawari
Distinguished Professor, Nuclear Engineering
Director, Nuclear Reactor Program
Department of Nuclear Engineering, North Carolina State University

Abstract

In the past few years, several concepts have been proposed as advanced thermal reactors.  This includes the Advanced High Temperature Reactor (AHTR) and the Fluoride High Temperature Reactor (FHR).  In all these concepts, neutron thermalization is a phenomenon that sets the physics of the reactor and impacts its operational and safety characteristics.  For such reactors, prompt neutrons are introduced by fission that undergo a slowing-down and thermalization process.  Once thermal, they attain a quasi-equilibrium energy spectrum that defines the neutron’s reaction rate with the system’s nuclei.  Fundamentally, the description of the thermalization process, in a given material, requires knowledge of the double differential thermal neutron scattering cross section (ds/dWdE).  This in turn requires establishing the thermal scattering law (TSL), S(a,b), of the material.  Traditionally, S(a,b) was calculated using simplifications motivated mainly by computational feasibility.  However, at NCSU we pioneered a modern approach that implements atomistic simulations in TSL analysis.  To date, much work was conducted to develop this approach and to define experiments for the validation of the generated data.  Among such experiments is the pulsed slowing-down-time technique for data validation in the thermal range.

Biography

Ayman Hawari is Distinguished Professor of Nuclear Engineering and Director of the Nuclear Reactor Program at North Carolina State University (NCSU).  He obtained a BS from the University of Missouri-Rolla and MSE and PhD from the University of Michigan-Ann Arbor, all in Nuclear Engineering.  His technical interests include fundamental research on neutron thermalization in matter, radiation measurements for data validation and materials nondestructive examination, and the development and utilization of intense radiation sources (e.g., research reactors and accelerators).  He chairs OECD/NEA’s subgroup 42 on “Thermal Neutron Scattering Law Data”, is a member of NNSA’s Nuclear Data Advisory Group (NDAG), and a member of the steering committee for the International Group on Research Reactors (IGORR).  His NCSU group is the primary contributor of thermal scattering law data to the recent Evaluated Nuclear Data File (ENDF/B-VIII.0) release.  He is a recipient of the NCSU Alcoa Foundation Engineering Research Achievement award and is a Fellow of the American Nuclear Society.

***This seminar will be streamed live on our NCStateNuclear YouTube channel***