Monte Carlo Analysis of Gamma-Ray Spectroscopy and AWCC Nondestructive Assay of Uranium-Oxide Samples

Year
2012
Author(s)
L.G. Chiang - Oak Ridge National Laboratory
L.G. Chiang - Oak Ridge National Laboratory
R.B. Oberer - Oak Ridge National Laboratory
R.B. Oberer - Oak Ridge National Laboratory
S.D. Clarke - Department of Nuclear Engineering & Radiological Sciences
S.A. Pozzi - University of Michigan
S.A. Pozzi - University of Michigan
M. Flaska - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
C.A. Gunn - Oak Ridge National Laboratory
C.A. Gunn - Oak Ridge National Laboratory
S.D. Clarke - Department of Nuclear Engineering & Radiological Sciences, University of Michigan
Abstract
Both gamma-ray spectroscopy and the active well coincidence counting (AWCC) are well- established techniques for the nondestructive assay of highly-enriched uranium (HEU). The AWCC was considered to be more appropriate for concentrated HEU product because gamma rays are attenuated by high-density, high-Z materials such as uranium. This is especially true of the lower-energy gamma rays emitted by the U-235. The low-energy gamma rays of U-235, however, are not the only source of information available with which to perform gamma-ray spectroscopic analysis on HEU. Virtually all HEU contains a small quantity of U-232. This isotope is co-mingled with the HEU and emits high-energy gamma rays through the Tl-208 daughter. The addition of these gamma rays to the analysis, to gauge the attenuation by the material, may provide penetrability as great as or greater than that provided by active neutron interrogation by the AWCC. In this work the Monte Carlo code MCNPX-PoliMi is used to investigate the depth of interrogation by each method in detail. A 4-kg U3O8 standard will be used for the comparison.