A technical fault has resulted in a complete shutdown of one of the nuclear reactors at Heysham Power Station.
EDF Energy, operators of the power plant, said one of the two reactors at Heysham 1 had to be closed down due to a water leak in a turbine in a non-nuclear part of the plant.
A spokesman for EDF said the plant had been taken offline as a precaution, after a “tiny” water leak had been discovered.
It could be days before the reactor is back online.
Heysham Power Station was previously closed in August 2014 following a routine inspection which discovered a fault.
A reactor at the site was also closed in May 2013 after smoke was seen coming from the plant.
EDF operates eight nuclear sites across the United Kingdom.