Improvements in Monitoring Enrichment of HEU Blend Down Under the U.S./Russian HEU Transparency Program

The enrichment monitor designed to monitor HEU being blended down into LEU under the HEU Transparency Program at three Russian facilities was designed at Los Alamos National Laboratory in 1995. It was based on through-the-pipe gamma spectroscopy using a 57Co (half-life 272 days) transmission source, a Bicron (St. Gobain) NaI(T1) detector, and an analog Canberra Inspector multichannel analyzer (MCA). This design was installed in the Urals Electrochemical Integrated Enterprise (UEIE) in 1999 and at the Electrochemical Plant (ECP) in 2003. The equipment has monitored much of the 320 metric tons that have been processed to date under the program since the HEU Purchase Agreement was signed in 1993. Over the years, the enrichment monitor has undergone significant improvement. In 2004 an improved system was installed in the Siberian Chemical Enterprise (SChE) using an 241Am transmission source, the same type of NaI(Tl) detector, and an ORTEC digiDART MCA. The system featured a permanent transmission source due to the 433-year half-life of 241Am, a digital MCA, and improved software. A similar 57Co-based system was installed at UEIE in 2005. A 57Co-based system is being planned to replace the current system at ECP.