Portable NDA Equipment for Enrichment Measurements for the HEU Transparency Program

In October 1996, the Department of Energy (DOE) and MINATOM agreed to use portable non-destructive assay (NDA) equipment to measure the 235U enrichment of material subject to the HEU Transparency agreement. A system based on the “enrichment meter” method and high-purity germanium (HPGe) detectors had been previously developed for this application. Instead, sodium iodide (NaI) detectors were chosen to measure 235U enrichment because HPGe systems might reveal sensitive information. Although the accuracy of the NaI systems is less than an HPGe system, it still satisfies the transparency requirements. The equipment consists of a collimated NaI detector, a Canberra Inspector Multi-channel Analyzer, and a laptop computer. The units have been used to confirm the enrichment of material at Russian facilities since January 1997. This paper compares the performance of the NaI systems with the HPGe system and discusses some significant differences.