WIPP Certification and Routine Waste Measurements Performed on the Large Box Assay System at the Savannah River Site

A comprehensive WIPP Certification of a Nondestructive Assay Box Counter (NABC) at the Savannah River Site (SRS) has been completed. This NDA System is presently WIPP Certified to assay Standard Waste Boxes (SWBs), Standard Large Box-2s (SLB- 2s), and 208-liter 55-gallon drums. Additionally, the system has the capability to assay Ten-Drum Overpacks (TDOPs). This NDA System contains two subsystems: a Box Segmented Gamma Scanner (BSGS) which has an efficiency-based calibration and one based on segmented transmission measurements, and a complementary Box Neutron Assay System (BNAS) passive neutron coincidence counting system. Presently, routine waste assays are performed on each waste container by the BSGS and BNAS. During normal operations, the waste container passes through the BSGS first. The four-HPGe detector gamma scanner performs both an efficiency-based and transmission-corrected quantitative scan, and an isotopic analysis. After the BSGS gamma scan is completed, the box is subjected to a BNAS assay for neutron coincidence counting. The neutron and gamma data from the BSGS and BNAS are subsequently automatically combined by a software engine called the multimodality results combiner to obtain a final set of results. Additionally, once the respective assays are completed, results from both gamma and neutron modalities are evaluated by an expert analyst. This report will summarize the standards and waste measurements performed to qualify the NABC system for TRU waste. Additionally, examples will be presented to illustrate everyday problems encountered by the expert analyst when reviewing waste assay data obtained from this NDA System.