The reactors were shut down as a precautionary measure in August 2014, following discovery of a crack in a boiler spine at Heysham 1 Reactor 1.
EDF Nuclear Generation Limited presented ONR with a safety justification for the return to service of Heysham 1 Reactor 2 and the two reactors at Hartlepool. ONR has completed an independent assessment of this justification and is satisfied that EDF has demonstrated the continued safe operation for these reactors.
EDF intends to present a separate safety justification for Heysham 1 Reactor 1 which will be subject to independent assessment and will require formal permission from ONR before the reactor can return to service.
ONR will publish its Project Assessment Report outlining its decision in due course.