- Nuclear inspectors are considering a safety review of
Sizewell B nuclear power station after corrosion was found to have almost
eaten away the vessel that holds the hot nuclear heart of a related American
nuclear reactor.
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- Checks were being conducted on 68 pressurised water type
nuclear reactors across America after workers at the Davis-Besse plant
in Ohio found that the head of the vessel had been so badly corroded that
it significantly raised the risk of a meltdown.
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- Engineers are still investigating why the corrosion occurred.
The damage is alleged to have been discovered by accident.
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- The Nuclear Installations Inspectorate said last night
that it was weighing up the implications for the Sizewell B plant in Suffolk,
Britain's only pressurised water reactor.
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- "We are aware of the incident at Davis-Besse and
have obtained technical information from the US."
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- A spokesman for British Energy, the operator of Sizewell
B, said the vessel would be inspected during the next shutdown.
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- "The reactor head is inspected at regular intervals
during planned shutdowns and then continually using a series of detectors."
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- Sizewell B also contains instrumentation to monitor the
pressure vessel and is much younger - at seven years - than the 25-year-old
plant in Ohio.
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- An inspection at the Davis-Besse plant caught experts
by surprise when they found a hole six inches deep, seven inches in length
and about five inches wide in the pressure vessel.
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- The corrosion left stainless-steel cladding around 0.375in
thick to contain cooling water under more than 2,200lb of pressure per
square inch. The pressure had bent the steel outwards by an eigth of an
inch over four inches.
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- The US Nuclear Regulatory Commission said vessel degradation
"can pose a significant safety risk".
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- If the liner had given way there would have been a serious
leak and it significantly raised the risk of a core damage - possibly a
meltdown - and a release of radiation.
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- The NRC said it had never seen so much corrosion in a
reactor vessel and that it was concerned about a dozen of the oldest plants
- one of which is part owned by British Energy.
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- The plants have to report by early April whether they
are safe enough to keep in service.
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- One factor is thought to be boric acid, used in cooling
water to absorb surplus neutrons, the subatomic particles that are released
when an atom is split and go on to split other atoms, sustaining the chain
reaction.
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- David Lochbaum, a nuclear engineer at the Union of Concerned
Scientists, a non-profit watchdog, said the discovery was troubling. "You
shouldn't get such a huge hole in a pressure-retaining vessel."
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- Edwin Lyman, the scientific director of the Nuclear Control
Institute, an anti-proliferation group, said the discovery was serious,
had generic implications, "and it was discovered by accident".
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- Workers stumbled on the problem in the process of fixing
a leaking tube that connects to the vessel head, which is 17ft in diameter.
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- http://www.telegraph.co.uk/news/ma
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