In order to efficiently plan for the decontamination of DOE facilities, the three-dimensional distribution of radioactive contaminants must be determined. Samples could be obtained for laboratory analysis, but this method could expose workers to radiation as well as spread contamination. On-site in situ measurements are preferred; however, no method currently exists for the in situ characterization of the contaminant depth profile, without a priori assumptions about the profile. The deficiency will be addressed by using gamma-ray spectroscopy with a number of collimators, each restricting the field-of-view to a different range of angles with respect to the surface normal, to characterize radioactive depth distribution in three-dimensional field surveys. Phase I will: (1) model the detector system to optimize the number and design of the collimators; (2) determine the minimal detectable activity using laboratory measurements of bare and attenuated sources, and (3) test the detector system on ground contaminated with Uranium mine tailings. Commercial Applications And Other Benefits as described by awardee: A detector system providing three-dimensional, in situ characterization should find use in the cleanup of radioactive contaminants from nuclear facility sites, Uranium mines and mills, reactor structures undergoing decommission, and from thick objects, such as waste drums. Remotely operated detectors can be built to avoid worker exposure.
