United States

The United States has a weapons program which began before 1970, and is still ongoing.

Military Stocks of Fissile Material, end of 2003 (in tonnes)1
Plutonium99.5 (±2%)2
  Military Stock47
  Declared Excess52.5
    Under Safeguards2
Highly Enriched Uranium (HEU)700 (±50)
  Primary Military Stocks34804
  Assigned to Naval Propulsion100
  Other Stocks5--6
  Declared Excess
    Remaining123
    Original174.37
      Under Safeguards10


1 From Global Fissile Material Inventories, June 2004.
2 The values in parentheses are the uncertainty ranges of the total estimated stock.
3 This category lists estimates of the primary military stocks that contain HEU, mostly weapon-grade, assigned to nuclear weapons, reserves, or slated for future use in naval propulsion, other military programs or civil reactors. In the case of the United States, some of this HEU will be sold or assigned to civil research reactors. This stock also does not include any HEU already declared excess to military requirements or already scheduled to be excess HEU, as in the case of Russia's commitment to down blend 500 tonnes of HEU into LEU.
4 This stock has an average enrichment of about 90 percent.
5 This category includes mainly HEU used in military production reactors.
6 The HEU in fresh and irradiated production reactor fuel is included in the excess value.
7 In late 1994, the United States declared as excess to military requirements about 174.3 tonnes of HEU (average enrichment is 60 percent). This stock is dynamic, in the sense that more HEU has been added to it and a significant amount has been blended down to low enriched uranium. Subsequent to its original announcement, the DOE has not released an updated value for this excess inventory. Through the end of 2003, about 51 tonnes of this HEU was blended down into low enriched uranium. About 48 tonnes were downblended by USEC for sale as power reactor fuel. About 3 tonnes of "off-spec" HEU were recently blended down for use in TVA power reactors starting in 2005. About a half tonne of HEU was blended down to slightly below 20 percent uranium 235 for use in research reactors. Subtracting the amount of HEU down blended from the original declared quantity leaves an excess stock of 123 tonnes as of the end of 2003.
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