Challenges of Non-Destructive Assay Waste Measurement

Historically, the Savannah River Site (SRS) routinely produced special nuclear material (SNM), which provided stable measurement conditions for the non-destructive assay (NDA) methods. However, the main mission of SRS has changed from the production of SNM to the processing of waste and material stabilization. Currently, the purpose of processing is to recover the SNM from the waste and stabilization materials, much of which is from other DOE facilities. These missions are usually of a short duration, but require non-destructive assay (NDA) accountability measurements on materials of varying composition and geometric configuration. These missions usually have cost and time constraints, which sometimes require re-application of existing NDA methods to waste measurements. Usually, each new material or re-application of the NDA method to a different SNM campaign requires new standards and timely re-calibration of the method. These constraints provide numerous challenges for the NDA methods, particularly in the area of measurement uncertainty. This paper will discuss the challenges of these situations, mainly from a measurement and statistical point of view and provide some possible solutions to the problems encountered. Specific examples will be discussed for the segmented gamma scanner (SGS), neutron multiplicity counter (NMC) and passive neutron coincidence counter (PNCC), which are some of the most common NDA instruments at SRS