Year
2012
Abstract
The Nuclear Materials Identification System (NMIS) at Oak Ridge National Laboratory (ORNL), although primarily designed for analyzing special nuclear material, is capable of identifying nonradiological materials by a variety of measurement techniques. This paper demonstrates methods, complementary to fast-neutron imaging, that can be used for material identification: 14.1 MeV neutron transmission measurements, 14.1 MeV neutron time-of-flight scattering measurements, and transmission measurements of fission spectrum neutrons from a time tagged 252Cf source. Each of these techniques was used to evaluate how these methods can be used to identify four materials: aluminum, polyethylene, graphite, and G-10 epoxy. While such measurements have been performed in separate applications in the past, in this study all three measurements were performed on the same set of materials. The results of calculations, which include MCNP-PoliMi simulations, agree well with these measurements. Results of this project demonstrate how NMIS can be used to carry out measurements of nonradiological materials using multiple techniques, and how these techniques complement each other to aid in materials identification. In particular, neutron scattering measurements complement data from 14.1 MeV transmission measurements by providing information about the nuclear mass of materials inside a sample, and 252Cf transmission measurements provide detailed information about the total neutron crosssection structure of a material over the energy range of the 252Cf fission neutrons. This project is part of a bachelor’s thesis project that investigates neutron interactions that supplement fast-neutron imaging for material identification. Another part of this project showed how active gamma-ray spectrometry can aid in the identification of these materials.