Year
1989
Abstract
The transfer of Special Nuclear Materials (SNM) between facilities is an activity that appears to be particularly vulnerable to theft or diversion. Precise measurements of an attribute of the SNM in the shipping containers can be used to confirm that the SNM was not tampered with during the shipping process. These measurements do not require a calibration. However, they should be based on an attribute that is unique to each sample. This confirmatory instrument performs gamma-ray measurements at three energies - 185.7 keV, 1001 keV, and 2614 keV. The instrument collects data for 200 s from sealed shipping containers (208-liter barrels). These measurements distinguish the issue of material control (has any material been diverted?) and the issue of measurement control (is there a measurement bias between the shipper's and the receiver's measurements of the same item?). This is an important distinction because the material control problems require prompt corrective measures while measurement control problems are never solved (they just get smaller). Sufficient material control to satisfy the regulatory requirements for shipper-receiver transfers is demonstrated with this technique. In-plant measurement data is shown to demonstrate measurement stability over both long and short periods. We also illustrate that the discrimination capability of the technique is adequate to distinguish between similar items.