Ministers are probing a new switch to nuclear energy

The strategy has been sparked by concerns over the security of gas supplies from countries like Russia.

Options would include extending the life of existing nuclear power plants or even building a new one - which could prompt environmental objections.

A series of power cuts have led to fears about guaranteeing supplies.

One example in London last year led to a loss of power which included part of the underground system.

Scotland has three nuclear power stations. Chapelcross in Dumfries and Galloway - which now being decommissioned - exports power to England.

Two others - Hunterston B in Ayrshire and Torness in East Lothian - meet 50% of Scotland's electricity demand.

British Energy said Hunterston should last until 2011 and it expected Torness to stay in production until 2023.

Decommissioning scheme

The news emerged as the operators of the Dounreay nuclear plant unveiled plans for its notorious disposal shaft.

The UK Atomic Energy Authority (UKAEA) outlined how it proposed to "stabilise" the shaft to prepare for the removal of all its radioactive waste.

The shaft was used as a store for dangerous material from the Caithness site.