Many long established US DOE facilities are in possession of poorly documented wastes in a variety of forms spanning a broad range of waste containers, waste matrices and isotopic mixtures. Existing assay technologies such as the SuperHENC can address many of the expected waste configurations. However, there are also expected waste items that fall outside the normal operating range of these exceptional but “standard” systems. Given the inherent difficulties and high costs associated with repackaging even a small number of these containers, an assay solution combining multiple techniques has been studied with the objective of maximizing the likelihood of successfully assaying waste for eventual shipment to WIPP or low level waste disposal. The Integrated Crate Interrogation System (ICIS) is comprised of a Box Segmented Gamma Scanner (BSGS) and a passive/active neutron counting system called the Super IWAS. These are two physically independent assay systems mounted within separate ISO Containers but connected via Ethernet to allow automated integration of the assay results from the two systems. In operation, the waste containers will first be assayed within the BSGS system to obtain both quantitative gamma-ray assay results and relative isotopic data using well-known algorithms such as the MGA or FRAM. In addition to scanning in front of an array of HRGSs the item is also stepped past a 60Co transmission station on the same line. The operator will then move the container to the neutron assay system. The Super-IWAS concept considered, based on the successful IWAS installations at the AMWTP, provides both highefficiency passive neutron coincidence analysis and active neutron interrogation using the Differential Die-Away technique (DDA). The prospect of combining all three complementary assay modes to provide a reliable assay result is discussed for realistic waste forms along with the extensive modeling results. Our objective was to devise an NDA solution to this pressing problem that stretched the current state of the practice but which could be implemented with low technical risk using a reasonably sized resource allocation in a predictable and timely fashion. At the conclusion of the study, a design without the DDA capability was selected for construction.
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