Field Use of NMIS at Oak Ridge

Abstract

The Nuclear Materials Identification System (NMIS), developed by the Oak Ridge National Laboratory and Oak , has been successfully used at Y-12 for nuclear material control and accountability (NMC&A). It is particularly useful in the high gammaray background of storage arrays and for shielded HEU. With three systems in use at Y-12, NMIS has enhanced the NMC&A capability for verification and for confirmation of materials in storage and for HEU receipts by providing capability not available or practical by other NDA methods for safeguards. It has recently costeffectively quantified the HEU mass and enrichment of hundreds of HEU metal items to within a total spread of ± 5% (3 sigma) with and mean deviations for all HEU verified of + 0.2% for mass and -0.2% for enrichment. Three cart portable systems are easily moved around with minimal impact on facility operations since no permanent dedicated floor space is required. The positive impact of NMIS at the Oak Ridge Y-12 Plant is improved and more cost effective NMC&A as well as the resolution of NMC&A findings. Its operation at the Y-12 Plant is essential for compliance with the NMC&A requirements of the U. S. Department of Energy. NMIS portability has allowed one system to be moved temporarily to the former K-25 Gaseous Diffusion Plant for characterization of a large deposit of hydrated uranyl fluoride. The impact of this NMIS application was enhanced and verified nuclear criticality safety that led to the safe removal of a large deposit originally estimated by gamma-ray spectrometry and neutron counting to contain 1300 kg of 3.3 wt% 235 U material. NMIS has also been operational at Los Alamos National Laboratory and Pantex.