Sizewell B power station was unexpectedly shut down shortly after 5pm on Wednesday.
A spokesman for the nuclear power station near Leiston on the Suffolk coast said: 'Sizewell B power station came offline at 17:11hrs today.
'This was an unplanned automatic shutdown. The reactor was safely shut down, with the plant responding as expected, and at no time was anyone's safety at risk.
'We are currently assessing the situation.'
•More to follow.
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