Small-angle Compton Scattering to Determine the Attenuation of Gamma Rays from HEU

摘要

Significant quantities of fissile material such as highly-enriched uranium (HEU) can accumulate in Cold War processing facilities, presenting a significant criticality safety issue. HEU accumulations can be found in waste materials, ventilation filters, process equipment, and support systems. For example, nondestructive assay (NDA) estimates of the HEU absorbed in concrete floors of chemical processing areas at Y-12 are tens of kg of HEU. However, these estimates vary greatly depending on the assumed depth of the HEU in the concrete. In addition to the use of differential attenuation, it was discovered that the discontinuity in the spectrum at a gamma-ray peak from small-angle Compton scattering can be used to estimate this depth. The use of this phenomenon is being developed at Y-12.