Conceptual Design of a Box Segmented Gamma Scanner for the Proposed Integrated Box Interrogation System, IBIS

Canberra Industries and LANL have collaborated in designing a next-generation Integrated Box Interrogation System, IBIS, to meet the requirements of the solicitation INEEL/EXT-99-00121 for boxed waste Non Destructive Assay Development and Demonstration. IBIS comprises a standalone Box Segmented Gamma Scanner, BSGS, and a trailer-mounted Box Segmented Neutron Scanner, BSNS, integrated by software to generate, from the wealth of complementary data the two sub-systems produce, a single, justifiable, best estimate assay result. This paper describes the BSGS. The main functionality of BSGS entails gamma assay of the crate to detect and quantify gammaemitting nuclides, particularly Pu and U isotopic measurements, and measurement of both matrix and source non-uniformity. Although based on proven hardware designs, the BSGS includes several innovations. The emphasis is on acquiring multiple distinct geometrical views of the waste. In combination with the neutron data acquisition system this results in a versatile instrument with the potential to record the most comprehensive set of assay data of any box counter to date. This data can be harvested using a rich variety of complementary techniques, permitting tomographic matrix corrections and (active) image spatial corrections to be extracted. Consequently, it is expected that the accuracy of assays will be improved, a wider variety of waste material may be assayed, and measurement results will require less dependence on á priori assumptions. This means that more containers of waste currently in interim store will be amenable to direct assay. A primary aim of the IBIS design is to at least double the fraction of the DOE’s boxed waste inventory that can be directly assayed with acceptable sensitivity and accuracy to meet regulatory compliance, while reducing the need for expert data review, intrusive intervention, and interim storage.