EMSP Project Number 65015 Final Report: Three-dimensional position-sensitive germanium detectors

Critical to the DOE effort to deactivate and decommission the weapons complex facilities is the characterization of contaminated equipment and building structures. This characterization includes the isotopic identification of radioactive contaminants and the spatial mapping of these deposits. The penetrating nature of the gamma rays emitted by the radioactive contaminants provides a means to accomplish this task in a passive, non-destructive and non-intrusive manner. Through conventional gamma-ray spectroscopy, the radioactive isotopes in the contaminants can be identified by their characteristic gamma-ray signatures and the amount of each isotope by the intensity of the signature emission. With the addition of gamma-ray imaging, the spatial distributions of the isotopes can simultaneously be obtained. The ability to image radioactive contaminants can reduce waste as well as help ensure the adequate protection of workers and the environment. For example, if equipment and building materials have been subjected to radionuclide contamination, the entire structure must be treated as radioactive waste during demolition. However, only partial removal may be necessary if the contamination can be accurately located and identified. Hand-held survey instrumentation operated in the near vicinity of the contaminated objects is a common method to accomplish this task. This method necessitates long data acquisition times, direct close access, and considerable worker exposure, as well as leads to imprecise information. In contrast, imaging devices operated at a distance from the contaminated objects can accurately acquire the spatially dependent gamma-ray emission information in a single measurement. Consequently, the devices can more efficiently discriminate between contaminated and non-contaminated areas of heterogeneous objects while at the same time reducing worker exposure