A Scottish nuclear power station has been shut down because of vibrations in the gas circulation system, which cools the reactors.

Reactor 1 at the Torness power station in East Lothian was closed down automatically on Monday afternoon.

A second reactor has been out of action since May because of a similar problem.

The operator British Energy said there was no "incident" in either case and no escape of radiation.

There are no immediate safety issues at Torness

NII spokesman

The news saw British Energy shares slump almost 40%.

The plant itself accounts for about 12% of its annual energy output.

A company spokesman said: "The Nuclear Installations Inspectorate has been informed and the station will remain closed for the foreseeable future."

He added there was no threat to the jobs of the 450 people employed at the plant, which usually produces 1,200 megawatts of electricity if both reactors are in use.

In June, Torness was closed for five days after lightning struck pylons nearby, tripping the station's safety system.

Review move

According to the company, the shut down happened because of vibrations in one of the gas circulators.

A similar problem shut down the number 2 reactor in May and investigations are continuing.

British Energy stressed that it was a mechanical problem and there were no safety issues involved.

The Nuclear Installations Inspectorate (NII) said it would review safety at all power stations run by British Energy.

A spokesman said: "There are no immediate safety issues at Torness. British Energy has kept us fully informed and has taken the appropriate action.

'Unreliable and unsafe'

"But British Energy and ourselves will be reviewing other stations to see whether there are any other implications."

Environmental campaigners, Friends of the Earth Scotland, claimed the shutdown demonstrated nuclear power was unsafe and warned similar such incidents in the future were "inevitable".

Chief executive Kevin Dunion said: "We can be thankful there doesn't seem to have been any radiation leak on this occasion.

"But this is proof that nuclear power is unreliable and unsafe and it's inevitable we'll see more of these shutdowns as these stations are past their sell-by date.

"They have had their lives artificially extended when they should not have."