The Scottish pollution inspectorate is at odds with two expert committees who, "over a relatively short timescale", want the pit dug out and decontaminated at a cost of between pounds 100m and pounds 500m.
But the inspectorate does not believe that the shaft represents an immediate risk to the public.
The committees 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.
Experts from the Radioactive Waste Management Advisory Committee warned that the 200ft shaft, which had been dug during the late Fifties, "is not an acceptable model for the disposal of radioactive waste." Modern standards require "a radical reconsideration of the safety of the shaft", they said.
They recommended that the waste be dug out and repackaged for disposal elsewhere and that the shaft itself should be decontaminated. This work would take between 15 and 20 years.
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 launched the detailed investigation into Dounreay.
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