The Making of Nondestructive Assay Standards to Resolve Shipper/Receiver Differences

Accurate quantitative Nondestructive Assay (NDA) of waste and scrap is difficult due to its heterogeneous nature. This becomes even more apparent when seeking measurement agreement of scrap measured on NDA equipment at different facilities calibrated with standards which have special nuclear material (SNM) placed in different configurations. Babcock & Wilcox (B&W) recently experienced a significant shipper/receiver difference with NDA measured combustible scrap sent to the Oak Ridge Y-12 facility. After extensive investigations, including remeasurement of a group of containers at both facilities (B&W and Y-12) using NDA systems and the recovery of the SNM by Y-12, it became apparent differences in the array of the SNM in the standards created a major part of the measurement problem. B&W has since developed a new set of standards with an SNM array that is different from previously used standards. Tests indicate that the use of the new standards created a calibration equation that provides sufficient agreement with the recovery values and the NDA measured values at Y-12. The use of these standards will reduce the shipper/receiver differences in the future. This paper describes the investigation and making of the new standards.