Oldbury nuclear power station has had a catalogue of problems this year. It has two reactors (named with great imagination Reactor 1 and Reactor 2). Each reactor has been stopped for various reasons. For months up to August both reactors were stopped, and it is a long time since both reactors were generating.

Both reactors are suffering from 'graphite depletion'. The core of the reactor is mostly made of a huge stack of graphite bricks, made of the same stuff as pencil lead. The uranium fuel rods are lowered into holes in the graphite bricks. The graphite gets gradually eroded, losing weight and strength.

The operators of the reactor (called BNG until recently) have to prove periodically to the nuclear inspectors (the NII) that the bricks are not cracked and are still strong enough not to be crushed. To do this, they do two things. Firstly they take the fuel rods out and put cameras in to inspect for cracks. Secondly they test the strength of spare bricks that have been sitting in a reactor, and are slightly more eroded than the ones that have load on them. A report is then written and the NII decide whether the reactor is safe to restart. To do this takes several months.

Reactor 2 went thought this process last winter, and was approved to restart in May. When it was started up again, a transformer component failed. This was fixed by replacing the transformer. When it was restarted the steam turbine vibrated more than it should, so it was shut down again. Meanwhile Reactor 1 has been shut down to go through the graphite depletion tests. So the Reactor 1 turbine was idle and has been switched to Reactor 2. Reactor 2 started generating at last in August.

The whole station will be shut down at the end of next year to comply with international agreements about pollution of the Irish Sea. The fuel rods from Oldbury get reprocessed in an ageing factory at Sellafield, which releases radioactivity into Morecombe Bay. So that will end the argument about whether the 40-year-old Oldbury should be shut for ever.

Alan

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