United Kingdom

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

Military Stocks of Fissile Material, end of 2003 (in tonnes)1
Plutonium7.6 (±2%?)2
  Military Stock3.2
  Declared Excess4.4
    Under Safeguards4.4
Highly Enriched Uranium (HEU)21.9 (±?)3
  Primary Military Stocks416
  Assigned to Naval Propulsion5-75
  Other Stocks6?
  Declared Excess
    Remainingn.a.
    Original0
      Under Safeguards0


1 From Global Fissile Material Inventories, June 2004.
2 The values in parentheses are the uncertainty ranges of the total estimated stock.
3 In 1998, Britain declared that it had 21.9 tonnes of HEU in its military stock. It did not declare any of this amount excess to military requirements, announcing that any HEU not required for nuclear weapons would be used instead in its naval propulsion program. In addition, the declared stock reportedly did not account for fission and transmutation of the contained uranium 235 in reactors, particularly naval reactors.
4 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.
5 The value assigned to the British naval propulsion program is highly uncertain, and most of this value would represent irradiated HEU stored in Britain. It has not been reduced by the amount of uranium 235 that fissioned in reactors. One would expect that on order of a tonne of uranium 235 fissioned.
6 This category includes mainly HEU used in military production reactors.
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