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Q&A on Plutonium/MOX | Safety issues around MOX fuel | MOX makes nuclear bombs | Plutonium Shipments |

Plutonium MOX fuel - weapons usable plutonium

British Nuclear Fuels Ltd, the UK government owned nuclear company, has denied that Mixed Oxide Fuel, (MOX) or plutonium fuel, is a threat to non-proliferation because even if you reprocessed the MOX, it would not be weapons grade material.

This statement together with others made by the nuclear industry are misleading as it implies only weapons grade plutonium can be used to make a nuclear bomb. The facts tell a different story.

The issue of whether plutonium is weapons grade or reactor grade depends upon the level of impure types of plutonium in the material. If a sample of plutonium contains over 93% of Plutonium-239 then it is classified in the US as weapons grade. In general, reactor-grade plutonium contains up to 60% Plutonium-239 with the rest being made up of Plutonium-240, Plutonium-241, and Plutonium-238.

However, the higher level of impure types of plutonium do not stop it from being used in a nuclear bomb. In June 1994, U.S. Energy Secretary Hazel O'Leary declassified further details of a 1962 test of a nuclear device using reactor-grade plutonium, which successfully produced a nuclear yield.

The British Government itself has recognised this test, as it used British reactor-grade plutonium from Sellafield, which BNFL owns and operates. The announcement, below, proved that reactor grade plutonium can be used in nuclear weapons;

HANSARD July 1994 - Col 82

Mr Aitken (Department of Defence): My department was consulted about the announcement by the United States Energy Secretary on 27 June that the United States had conducted in 1962 a nuclear test explosion using reactor-grade plutonium of British origin. We agreed to this information being released...
The 1962 test confirmed the technical feasibility of constructing a nuclear explosive device using reactor-grade plutonium. This fact was declassified by the United States in 1977. There are, though, significant technical difficulties which would complicate the manufacture and storage of any weapon based on reactor-grade plutonium. It remains our policy that all grades of plutonium should be rigorously protected, and in accordance which our international nonproliferation obligations, stringent controls are applied to all forms of plutonium.

The quantity of plutonium used to destroy Nagasaki in 1945, was 6.1 kg. The weapons grade plutonium in the bomb had an explosive force of around 20 kilotonnes (20,000 tonnes of TNT equivalent). With reactor grade plutonium similar to that in plutonium MOX fuel, the explosive force would be around 3.5 kilotonnes (3,500 tonnes of TNT equivalent). This size of nuclear explosion still represents a very terrifying nuclear weapon capable of destroying a major city centre.

As to whether reactor grade plutonium is suitable as a weapons fuel it is worth noting the views of U.S. nuclear weapons designer J. Carson Mark former director Theoretical Division of Los Alamos National Laboratory - US Nuclear Weapons Facility:

"Reactor-grade plutonium with any level of irradiation is a potentially explosive material. The difficulties of developing an effective design of the most straightforward type are not appreciably greater with reactor-grade plutonium than with those that have to be met for the use of weapons-grade plutonium."

Further even the Intemational Atomic Energy Agency (IAEA) which is in charge of policing international nuclear proliferation safeguards on nuclear materials recognises that reactor grade plutonium can be used in nuclear weapons. In 1990 Hans Blix, Director-General of the International Atomic Energy Agency (IAEA) stated:

"On the basis of advice provided to it by its Member States and by the Standing Advisory Group on Safeguards Implementation (SAGSI), the Agency considers high burn-up 'reactor grade' plutonium and in general plutonium of any isotopic composition with the exception of plutonium containing more than 80 percent Pu-238 to be capable of use in a nuclear explosive device There is no debate on this matter in the Agency's Department of Safeguards."

Further the IAEA has produced estimates of the length of time it would take to produce plutonium that would be suitable for use in a nuclear weapon from different types of the original plutonium;


Original Material Form End Process Form Estimated Conversion Time
Plutonium metal Finished plutonium Order of days 7-10
Plutonium nitrate or oxide Finished plutonium Order of weeks 1-3
Mixed Oxide fuel or powder Finished plutonium Order of weeks 1-3
Plutonium in irradiated fuels Finished plutonium Order of months 1-3

Also the U.S. Nuclear Regulatory Commission that licenses nuclear facilities in the U.S. has stated that:

"...So far as reactor-grade plutonium is concerned, the fact is that it is possible to use this material for nuclear warheads at all levels of technical sophistication. In other words, countries less advanced than the major industrial pcrwers but, nevertheless, possessing nuclear power programs can make very respedable weapons. ...Of course, when reactor-grade plutonium is used there may be a penalty in performance that is considerable or insignificant, depending upon the weapon design. But whatever we might once have thought, we now know that even simple designs, albeit with some uncertainties in yield, can serve as effective, highly powerful weapons - reliably in the kiloton range." (2)

1.    IAEA, IAEA safeguards Glossary, IAEA/SG/INF/1 (Vienna, IAEA, 1980) p.21; cited in Dr. L.S. Scheinman, "The IAEA and World Nuclear Order" Resources for the Future, 1987. p.165.
2. Gilinsky, V, "Plutonium, Proliferation and Policy" Commissioner, U.S., Nuclear Regulatory Commission, MIT, November 1, 1976, p.10-11.