The other three reactors at Hartlepool and Heysham 1, which were shut down as a precautionary measure, returned to service in November 2014.
EDF Nuclear Generation Limited presented ONR with a safety justification for the return to service of Heysham 1 Reactor 1. ONR has completed an independent assessment of this justification and is satisfied that EDF has demonstrated the continued safe operation for this reactor, with the affected boiler isolated from service. The reactor returned to service on Saturday 10 January 2015.
ONR will publish its Project Assessment Report outlining its decision in due course.