NUCLEAR officials praised safety systems at the Sizewell A plant in Suffolk last night after a reactor "tripped" – causing a loud bang and clouds of what appeared to be smoke to blow into the air.

By Danielle Nuttall

NUCLEAR officials praised safety systems at the Sizewell A plant in Suffolk last night after a reactor "tripped" – causing a loud bang and clouds of what appeared to be smoke to blow into the air.

An investigation is under way into what caused the fault, which happened just after 7pm last night and sparked a number of calls to police from alarmed residents.

Police and firefighters arrived at the site but British Nuclear Group, which owns the nuclear power station, immediately confirmed the vapour was clean steam and not radioactive, caused by a reactor tripping and shutting down.

However, a spokesman for the company admitted last night that a reactor shut down would be "commercially costly".

The alarm was raised shortly after 7pm when a member of the public contacted Suffolk police reporting they had heard a loud bang and witnessed smoke blowing out of the power plant.

Engineers at Sizewell informed police reactor two at the site had tripped and safely shut down, stressing that no radioactive material had leaked into the atmosphere. It is not yet known what caused the incident.

Colin Bennett, a spokesman for British Nuclear Group, said there was no risk to workers or members of the public as a result of the incident and that all the safety systems had operated correctly.

However, the temporary loss of part of the station would be commercially costly, he added.

"Reactor two has tripped which means it shuts itself down automatically. Because it's a pressurised system, when you trip a reactor you then have to depressurise the system and you dump steam," he said.

"It comes out of the station at a very high pressure and it's very noisy. It's the steam that appears to have caught the attention of the locals and we are sorry about the noise.

"There are a number of safety systems that kick in. Emergency services did attend but there are no safety problems. There was no release of radioactive material at all. It's a perfectly normal safe shut down of reactor.

"What it means we have lost one half of Sizewell A station, which is commercially costly. Clearly we will try and get the reactor up as soon as we can."

A spokeswoman for Suffolk police said: "Police received a call from a member of the public just after 7pm this evening reporting that they heard a bang and had seen a cloud of what appeared to be smoke emanating from Sizewell A power plant.

"Police contacted Sizewell to confirm that reactor two had tripped blowing steam into the atmosphere. Sizewell engineers have informed police that this release is not radioactive and the reactor has been safely shut down.

"Officers and the fire service initially attended the scene and have now been stood down. There are no reports of any injuries."

One of the twin reactors at the Sizewell A power station was shut down in March after a large transformer suddenly failed.

With the power station due to close in 2006, the British Nuclear Group had to decide whether the reactor should, on economic grounds, be closed down earlier than expected.

However, a decision was made to order a £2million replacement transformer. The transformer is now being manufactured and likely to be installed by engineers at the end of November.