Campaigners have repeated their demands for ageing Oldbury nuclear power station to be shut permanently. The calls come as nuclear regulators take a long look at information on the degradation of material in the core of one of the twin reactors. The 36 year old reactor has been shut since May last year and its routine inspection became extended as the Nuclear Installations Inspectorate asked for further samples and analysis of the lost graphite to decide how much this will impact on safety. Normally an “outage” would take no more than a couple of months, leading to speculation the reactor may not return to operation.

picture © of British Nuclear Fuels plc (BNFL)

Anxiety on restarting the reactor may be increased due to simultaneous graphite moderator core faults discovered in a much newer reactor at Hartlepool, where reactor core bricks have been found to have cracked, with important safety implications for all similar reactors. In many of its engineered and performance features, the Magnox type at Oldbury was a prototype for the AGR at Hartlepool.

Jim Duffy from Stop Hinkley, who has been campaigning to shut Oldbury for several years said, “Oldbury is known to have the worst graphite problem of all the Magnoxes, most of which have already shut down. Corrosion of the graphite caused by years of operating at higher temperatures than its Magnox predecessors could have weakened the structure of the reactor core, running the risk of a disaster. Now that cracks have opened up at Hartlepool, the only safe thing must be to shut this ageing power station permanently.”

The plant is due to cease operating in 2008 but its second reactor is due to shut for inspection in June this year and will require prolonged in situ assessment and a review of its nuclear safety case. Stop Hinkley has asked for details of the decisions on Oldbury's reactors under the new Freedom of Information Act.

Jim Duffy said, “The public has a right to know what's going on here now, before the reactor is started up again, for all our sakes. It would be very wrong to restart without putting us in the picture with all the detail. It's like starting an old car that has been left in a field for months, once the engine is restarted it's bound to blow out clouds of toxic dust and might even go bang.”

The graphite reactor core or 'moderator' acts to slow down the neutrons from the uranium fuel sufficiently to cause the nuclear fission which generates heat. In the Magnox reactors the graphite was expected to become depleted over the 20 to 30 year life expectancy but at Oldbury in 1986 this was found to be much faster than in other reactors.

In 1995 a Nuclear Electric report predicted a 48 per cent depletion of graphite in certain areas at the base and periphery of the reactor cores to have occurred by 2003. This was later increased to 55 per cent.

In the original design, methane gas was introduced with the carbon dioxide coolant in an attempt to reduce the rate of graphite degradation but this, in itself, accelerated corrosion in internal steelwork and was abandoned with an accompanying reactor temperature (and power) derating.

Oldbury is owned by British Nuclear Group, formerly known as BNFL.