CLAIMS that Oldbury nuclear power station is showing dangerous signs of age have been rejected out of hand by station chiefs.

Government nuclear safety watchdogs this week gave the go ahead for the power station's 36-year-old number one reactor to be returned to service after a seven month shut down for extended safety checks on its graphite core.

But other equipment problems - on the non-nuclear side of the plant - have also come to light and the reactor is to remain switched off for an indefinite period to allow fresh engineering inspections to go ahead.

The station's two "old tech" Magnox reactors are due to cease generating electricity in just under four years time when the plant will be 40 years old.

But anti-nuclear groups are now renewing their demands for closure to be brought forward on safety grounds.

The Shut Oldbury group - backed by members of Gloucestershire Green Party - claim the station is wearing out fast and should be shut down permanently ahead of the December 2008 closure date.

Campaign co-ordinator Jim Duffy said he was seeking information about problems at Oldbury under the new Freedom of Information Act.

"The public has a right to know what is going on here now, before the reactor is started up again, for all our sakes," he said.

"It would be very wrong to restart it without putting us in the picture with all the detail. It's like starting an old car that has been left in field for months. Once the engine is restarted it's bound to blow out clouds of toxic dust and might even go bang."

Martin Whiteside, prospective Green Party Parliamentary candidate for Stroud and a Stroud district councillor, said: "We welcome the thorough investigation into the problems at Oldbury but these reactors were expected to close in 1993. They were just not designed to last this long.

"We are playing Russian roulette to keep this ageing monster running while key components are clearly not working. We should close Oldbury now."

Consent for the reactor to be restarted was withheld until investigations were carried out into the condition of its graphite core - a vital part of the nuclear fission process but one which is subject to gradual depletion.

The reactor - one of two at the Severnside atom plant - was shut down last May for routine inspection and maintance and was due to be returned to service in July.

But the additional checks and sampling took several months and cost operators British Nuclear Group around one million megawatts of lost electricity generation.

Now the losses are set to continue with the decision to delay returning the reactor to service despite the green light from ultra-strict Government regulators.

Station spokesman Tim Jones said the discovery of possible defects in generation equipment on the non-nuclear side of the plant was entirely unrelated to the issue of graphite core safety.

"We may have to carry out remedial works to one of the two large steam turbines on the conventional side of the plant," he said. "This has nothing to do with the nuclear process and is ther sort of equipment also used in a conventional power station. It is quite a large piece of machinery which is driven by steam at very high pressure.

"Unfortunately, it involves an inaccessible area and therefore we shall not be restarting reactor one until investigations have been carried out and we have assessed all the options. At the moment we cannot predict a time scale for this."

However, said Mr Jones, the NII decision to allow reactor one to be re-started demonstrated that the safety case had been properly made out.

Gradual graphite weight loss in the reactor core was a well known pnenomenon, he said. "We have been aware for many years of radiolytic oxidisation of graphite and the condition of the cores of all Magnox reactors have been monitored closely for decades.

"There is a vast volume of evidence about the behaviour of graphite in nuclear reactors all over the world. This enables scientists to predict the condition of the cores and samples of graphite are taken regularly to confirm the accuracy of the predictions"

He said the additional tests and sampling carried out at Oldbury had enabled scientists to fully update the safety case as requested by the NII. As a result they had now given consent for start-up.

The station had detailed plans for ongoing monitoring, said Mr Jones.

Nuclear Installations Inspectorate spokesman Mark Wheeler said "The specific safety case for re-starting this particular reactor at Oldbury has been accepted. In order for the regulators to be satisifed, the licence holders had to produce some pretty robust data to show there had been no degradation of safety levels."

Oldbury's reactor number two is currently operating normally but is due to be taken out of service for 60 days this summer for its own statutory maintenance shut down.