Summary and Lessons Learned of the IAEA Safeguards Implementation at a Highly Enriched Uranium Downblending Facility

The BWX Technologies (BWXT) Downblending Facility converted approximately 50 metric tonnes (MT) of highly enriched uranium (HEU) into approximately 750 MT of low-enriched uranium (LEU) from 1999 through 2006. The project was conducted under International Atomic Energy (IAEA) safeguards to demonstrate the irreversible removal of HEU from U.S. national security programs. The facility downblended HEU that had been deemed excess to U.S. national security needs into LEU that was sold by the U.S. Enrichment Corporation (USEC) for fabrication into nuclear power reactor fuel. Because of the goal of the program and the large annual throughput of the facility, a unique IAEA safeguards approach was developed to effectively and efficiently verify the downblending activities. The IAEA safeguards approach used unattended on-line measurements to verify the nuclear materials flows through the downblending process equipment using in-line solution flow monitors and on-line gamma spectrometers. The volumes, uranium concentrations, and U-235 enrichments of the input and output streams were measured and volume, uranium, and U-235 balances were calculated for each downblended batch. Flow rates and enrichments observed between monitors on the piping and downblend vessels were tracked and compared to evaluate consistency of operations. This paper discusses the challenges, accomplishments, and lessons learned for the safeguards verification effort.