The Scottish pollution inspectorate is at odds with two expert committees which reported on Tuesday that in 1977 there had been a violent chemical explosion in a nuclear waste shaft which had scattered fragments of irradiated reactor fuel around the site and on to the beaches.
In their report, experts from the Radioactive Waste Management Advisory Committee (RWMAC) warned that the 200ft shaft, which had been dug during the late 1950s, "is not an acceptable model for the disposal of radioactive waste". Modern standards require "a radical reconsideration of the safety of the shaft".
They recommended that the waste be dug out and repackaged for disposal elsewhere and that the shaft itself should be decontaminated. This work will take between 15 and 20 years and estimates of the cost range from pounds 100m to pounds 500m.
The experts' conclusion that Dounreay should act urgently "to put in place a modern waste management regime for the shaft" was strongly endorsed by Comare, the Committee on the Medical Aspects of Radiation in the Environment, which had instigated the investigation into pollution at Dounreay.
But the Scottish Industrial Pollution Inspectorate believes it is "unresolved" as to whether it would be viable to remove the waste from the shaft as suggested, according to a Scottish Office spokeswoman. The Inspectorate's regulates discharges of radioactivity from the site and it has to assess whether decontaminating the shaft might not spread more radioactivity than it cleaned up, she explained.
The Inspectorate "are not convinced it would be do-able. How would you protect the workers who would carry it out? Is there any risk of another explosion - that has to be balanced against the risks of leaving it there. The view is that decontamination is not an easy option."
The expert's report concluded that "it is improbable that the waste could be immobilised in situ" and warned that "the shaft is very close to the cliff which is subject to strong wave attack and is likely to be breached within the next hundred years".
Although the explosion took place in 1977, experts investigating the incidence of childhood leukaemias around Dounreay had not been told of its existence until recently. The experts were told that the particles found on beaches in the area since 1984 had come from a minor spillage which had been washed away into a storm drain. As recently as May 1994, Comare was told that "there was no contamination associated with the 1977 explosion".
In fact, the explosion deposited a concentration of radioactive material on the turf at the top of the cliff from which metallic particles are still dropping on to the beach. But it was only after RWMAC and Comare started to investigate the explosion that Dounreay managers surveyed the site itself and started to discover "clustered particles" within Dounreay itself. The extent of the contamination is not yet clear.
Waste was disposed of into the shaft from 1959 to 1971, with smaller amounts being put down in 1973, 1974, and 1977, the year of the explosion. The crudity of the methods used is detailed in the report: "raw waste was carried to the site suspended by a rope in an open-bottomed flask. The flask was placed over the shaft, the rope was cut and the package fell into the shaft. Waste, including floating items, is visible at the water surface to the shaft."
Even though it is only 65 metres deep, the shaft had been licensed for intermediate waste disposal by the Scottish pollution authorities. The waste repository which UK Nirex hopes to build near Sellafield in Cumbria will be between 600 and 800 metres underground, but although this will be 10 times deeper than the Dounreay shaft, its long-term safety has been criticised.
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