THE Government's nuclear inspectors yesterday ordered the shutdown of Dounreay's entire fuel cycle area, including all its processing and reprocessing plants, following the safety fiasco which knocked out power supplies last week.

The move will be of huge embarrassment to the Government: the closure covers the crucial sections of the plant destined to handle nuclear waste imported from the former Soviet Republic of Georgia, amid great controversy, only two weeks ago.

It puts on hold the production of cancer treatment aids from the material.

The action is claimed to be unprecedented in the history of the British nuclear industry.

It is expected that it will take, at the very least, two years and many tens of millions of pounds to make the fuel cycle area safe, an investment in time and money that will just not be worth it, anti-nuclear critics warned.

The SNP described it as the ''the last straw'', repeated calls for a public inquiry and, in Parliament today, will call for the publication of a document hitherto blocked by Dounreay.

Scottish Industry Minister Brian Wilson, who had been involved in a bitter public debate with SNP leader Alex Salmond over the Georgian fuel, welcomed the announcement yesterday.

He said: ''This is a proper response by the Nuclear Installations Inspectorate (NII) of the Health and Safety Executive (HSE) and will provide a necessary public reassurance until this incident is fully investigated.''

The inspectorate took its decision after it emerged that a workman in a digger managed to cut off both mains and back-up power to the fuel cycle area last Thursday. The Herald has since learned that Dounreay waited for almost 12 hours before informing the regulatory bodies of the crisis.

The 5kg of nuclear fuel from Georgia is being stored there and management at the Caithness plant yesterday confirmed that the work to process the 4.2kg which is not irradiated, into materials for cancer treatment, is now indefinitely postponed. The work had been due to begin at the end of the month.

The HSE issued an official statement yesterday afternoon: ''The direction issued by the NII requires UKAEA to keep shut down all processing activities in the fuel cycle area, other than those operations and activities which are necessary to maintain the safe condition of the facility. HSE's consent will be required before these activities can be restarted.

''Before HSE will give its consent, UKAEA will be required to submit a safety case which demonstrates that the plants in the fuel cycle area are safe for a restart of normal operations. This will involve checks on the necessary integrity of the electrical supply system and that no con- tamination has occurred as a result of the incident on May 7.''

Dounreay's other official regulator, the Scottish Environment Protection Agency, backed the move: ''Sepa fully supports the decision of its fellow re-gulator,which has prime responsibility for regulating nuclear safety at the Dounreay site. Sepa will be consulted by the NII before the restart of activities.''

Dounreay director Dr Roy Nelson said that Dounreay was '' ... fully committed to producing a safety review which would satisfy itself and the NII of the safe operation of the area''.

Meanwhile, a Dounreay spokeswoman confirmed that the fuel cycle area's loss of power was not reported to the NII or Sepa until ''first thing Friday morning''.

Mrs Lorraine Mann, convener of Scotland Against Nuclear Dumping (Sand), described the delay as appalling. ''If the complete loss of power at a nuclear plant is not an emergency, what on earth is? Dounreay doesn't seem to know what constitutes an emergency, which is quite terrifying.''

Of the shutdown, she said: ''The regulator acting in this way is quite unprecedented. They have issued directions to close small parts of plants but not a series of plants as in the fuel cycle area. It confirms that, at very least, Thursday's breach of safety was the worst breach since the Dounreay shaft explosion in 1977.

''I suspect they will find it is not only the electrical systems which will have to be replaced. It is the taxpayer who will have to foot the cost, tens upon tens of millions of pounds.''

The SNP's environment spokeswoman, Roseanna Cunningham, said: ''The NII produced a report on the inadequacies of Dounreay's fuel cycle area some time ago.

''They have been willing to release it, but UKAEA have refused to allow them to. I will now be asking the Department of Trade and Industry if they are willing to place this document in the Commons Library, as it is clearly a matter of public concern.

Greenpeace's Mike Townsley called for the plant to be permanently closed. ''No amount of paper work can make this plant safe. It must now never reopen.''