Security at Sellafield has been stepped up

An exercise was held on Wednesday to test the county's ability to deal with a major off-site disaster, such as a radioactivity leak.

Brian Watson, the head of the Sellafield site, says security and safety are constantly under review in the current international climate.

He said: "The world scenario does change and it changed for everyone at 9/11 and we have responded completely to that.

"We are very confident in our arrangements but we are not arrogant about them. We do not stand back and think we have got to the end game.

"We are continually in the game of improving the arrangements so they are the best they possibly can be."

Airport fears

Meanwhile, delegates at the Liberal Democrats' party conference have been warned that terrorists are looking for targets outside London - and this could include Sellafield.

The Home Affairs spokesman, Simon Hughes, said nuclear sites and army camps could be among their targets.

He also warned they may strike train stations and provincial airports, such as Manchester and Glasgow.

Delegates backed a motion demanding an urgent reappraisal of civil defence, and that a Cabinet minister be given responsibility for co-ordinating emergency planning.