Kenny MacIntyre: "The phased run-down will essentially begin after the announcement on Friday"

The Scottish Secretary, Donald Dewar, and the Energy Minister, John Battle, will reveal the full details on Friday morning.

They are expected to announce that no new nuclear material will accepted for reprocessing at the coastal plant in Caithness.

However, existing waste which includes a consignment from the former Soviet republic of Georgia, will be dealt with, although not until the plant is given the all-clear by safety inspectors.

The announcement will be made by Donald Dewar

But from then on the focus will be on winding-down the plant, with all efforts being channelled towards clearing up the nuclear waste in the plant's underground shaft.

Dounreay, which was built in the 1950s, has been dogged by a string of controversial incidents, many since the start of the year.

But those hoping to see a swift end to the plant will be disappointed as experts predict decommissioning will take a generation.

Lorraine Mann of Scotland Against Nuclear Dumping: "Scotland will breath a huge collective sigh of relief"

BBC Scotland's industry correspondent Kenny MacIntyre said the latest announcement was rooted in the swathe of bad publicity surrounding Dounreay.

"Mr Dewar felt the real reason that all this material came into the public domain was because in a sense Dounreay had become more open," he said.

The plant provides much-needed employment in the area

"There was a feeling that if something wasn't done quickly there would be a mass scare in Scotland about the impact of Dounreay.

"They've decided to bring the whole closure process forward."

But although many will cheer the news of Dounreay's demise, there is concern about future employment prospects in the area.