Furthermore, the uranium's absence (or, if it turns up, its presence) will not affect Dounreay's future operations. The plant is already being "decommissioned" - shut down and dismantled - though its highly radioactive nature means the process will take decades.
According to a report issued by the UK Atomic Energy Authority, 170 kilograms (374 pounds) of uranium may be unaccounted for from the plant's early years of operation, between 1965 and 1968. But Dr John McKeown, chief executive of UKAEA, insisted that the huge discrepancy arose through accounting errors dealing with many small shipments.
The material was not stolen, nor transferred into the UK's then-nascent nuclear weapons programme, he insisted. But if it were still there, "it would be detectable," he added. Instead, an overestimate of just 1 per cent of the amount arriving from other sources would explain the discrepancy, he said.
Despite appearing incredible, the explanation was accepted yesterday by representatives for the Nuclear Installations Inspectorate (NII), which has nine inspectors on the site just starting a three-week audit of management practices and controls.
The NII has the power to withdraw Dounreay's licence to operate as a nuclear facility, and has already forbidden it to carry out reprocessing work until a number of faults are cleared and ageing equipment improved. As a result, the plant is now simply ticking over. The latest news will not affect that.
"These are totally historic figures from the 1960s," said a spokesman for the NII yesterday. "The figure emerges from an inventory of what is in the waste shaft on the site. It's a paper discrepancy; there may have been no real loss of fuel." The "missing" material - known as MUF, or "material unaccounted for" - might also lie in areas of the plant which have been shut down and are awaiting decommissioning.
Within the nearby town of Thurso, for which Dounreay with a workforce of 1,400 is the main employer, the reaction to yesterday's news was one of resignation. But it was mixed with pleasure at the news that a battery factory is soon to start up, creating more than 100 jobs in the coming years. It is the result of a deal between two major Japanese corporations and AEA Technology - ironically, a spin-off company from the UKAEA, which operates Dounreay.
But the nuclear plant has many local defenders. "They may have had crises at that plant, but say this for them, they have never had a fatal accident," said Elizabeth Macdonald, a local councillor in Thurso who has lived in the town since Dounreay was being built. "It has never had a Piper Alpha disaster. If you go to the coal mines or the gas industry's record then I think you would have to say it's safer than those others.
"They have to go back to the Sixties to find these faults. But Dounreay was put here as an experimental plant. I think that they learnt as they went along, so I'm sure that they made some mistakes. But I think that if they hadn't struck oil in the North Sea, then Dounreay would still be working."
However, Lorraine Mann, of the pressure group Scotland Against Nuclear Dumping, called Dr McKeown's explanation "patronising" and said that "total incompetence is matched by complete complacency".
For the Scottish National Party, Roseanna Cunningham said: "We are now in the ludicrous situation where we are hoping the uranium was used to make British atom bombs, because the alternatives are even harder to stomach."
The UKAEA report aimed to be a "worst-case" view of the possible contents of the waste disposal shaft at the site. Originally intended to hold radioactive and other waste materials indefinitely, the shaft is 220 feet deep and contains an estimated 15,000 tonnes of waste, including uranium and plutonium mixtures, as well as metal, clothes and other rubbish. It was seriously damaged in 1977 when there was an explosion inside it, reckoned to be caused by sodium and potassium coming into contact with water.
Scientists now plan to spend about pounds 500 million on freezing and then removing the shaft and its contents before vitrifying them for long-term storage.
It will probably be seven years before anything is removed. The NII, which will oversee the work, says: "We don't set time limits. We just make sure that they have to do it safely."Reuse content