Plant used to convert spent N-fuel

The UK Atomic Energy Authority's Dounreay plant in Scotland is a reprocessing facility, used since the 1950s to convert spent nuclear reactor fuel and other nuclear waste into fresh reactor fuel.

Material from Dounreay was not used for nuclear weapons development, a spokesman for the UK Atomic Energy Authority (UKAEA), Mr Morris Grant, said yesterday. "No material ever went out of Dounreay for weapons," he insisted, but he acknowledged that the missing material would have been "highly enriched" uranium.

It was wrong, he said, to state that up to 170 kg of enriched uranium might have gone missing from the plant. This figure was an estimate based on assumptions made in 1963 and again in 1973 about the amount of enriched uranium that might have been recoverable from the 17 tonnes of waste processed at Dounreay.

He said it was possible "that the material never actually existed" due to uncertainty in estimates of the amount of waste uranium coming into the plant. Dr John McKeown, chief executive of the British Atomic Energy Authority, said yesterday that while the uranium was unaccounted for, it could not have been stolen from Dounreay. The missing material came to light following the publication of an UKAEA inventory of waste dumped in an underground shaft on the Dounreay site. Mr Grant said an estimated 22 kg could be recovered from waste left in the shaft.

Nuclear power plants and some nuclear weapons are based on the splitting of large uranium atoms. This process is called fission and it gives off a great deal of energy.

Ordinary uranium would not work in nuclear power plants or weapons because it cannot be easily split, but a uranium isotope, U235, can be used in fission reactions.

Refined uranium ore only contains about 0.7 per cent U235, explained Mr David Pollard, manager of the environmental lab at the Radiological Protection Institute of Ireland. Levels of U235 can be increased, however, through a process called "enrichment". U235 levels are enriched to about 3 per cent for most power plant fuels he said. Higher enrichment levels are needed for weapons grade uranium.

File picture of the UK Atomic Energy Authority's nuclear reprocessing plant in