In 1996, the Department of Energy (DOE) announced plans to reduce the proliferation threat from stockpiles of surplus highly enriched uranium (HEU) by down-blending, or converting, it to low enriched uranium (LEU). In this form, the material can be used as commercial nuclear reactor fuel and is unsuitable for use in nuclear weapons. This provides a number of nonproliferation and energy-related benefits for the United States.
Surplus HEU is currently stored at several DOE facilities, but primarily at NNSA's Y-12 National Security Complex (Y-12) in Oak Ridge, Tenn. When ready for down-blending, it is shipped to a private sector facility in Erwin, Tenn., or down-blended at DOE/NNSA facilities located at the Savannah River Site in Aiken, S.C., and Y-12. All shipments of surplus HEU are moved using NNSA's secure transportation system designed to ensure the safety and security of sensitive government material.
To date, approximately 186 metric tons (MT) of HEU has been slated for down-blending, as it becomes available. Of this amount, more than 143 MT of HEU has already been down-blended to LEU or delivered for near-term down-blending. This amount represents enough for more than 5,500 nuclear weapons. The remaining balance of HEU slated for down-blending is expected to be completed as additional nuclear warheads are dismantled.
Down-blending projects to date include:
- 47 MT of surplus HEU was transferred to the United States Enrichment Corporation (USEC) and was down-blended into LEU commercial nuclear reactor fuel (project completed June 2006);
- 45 MT of surplus HEU has been down-blended for use as fuel in Tennessee Valley Authority reactors (completed in October 2011);
- 22 MT of surplus HEU has been set aside for down-blending to produce LEU research reactor fuel (over 4 MT has already been down-blended);
- 17 MT of HEU has been down-blended (completed in December 2012) to create the American Assured Fuel Supply (formerly called the Reliable Fuel Supply);
- 9 MT HEU has been down-blended for the MOX LEU Backup Inventory Project, and another 3 MT HEU has been delivered. All down-blending will be complete by mid FY 2015.