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

摘要

Both gamma-ray spectroscopy and the active well coincidence counting (AWCC) are wellestablishedtechniques for the nondestructive assay of highly-enriched uranium (HEU). TheAWCC was considered to be more appropriate for concentrated HEU product because gammarays are attenuated by high-density, high-Z materials such as uranium. This is especially true ofthe 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-rayspectroscopic analysis on HEU. Virtually all HEU contains a small quantity of U-232. Thisisotope is co-mingled with the HEU and emits high-energy gamma rays through the Tl-208daughter. The addition of these gamma rays to the analysis, to gauge the attenuation by thematerial, may provide penetrability as great as or greater than that provided by active neutroninterrogation by the AWCC. In this work the Monte Carlo code MCNPX-PoliMi is used toinvestigate the depth of interrogation by each method in detail. A 4-kg U_3O_8 standard will beused for the comparison.