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Britain's Hunterston B nuclear reactor to remain offline for safety checks-regulator

LONDON, May 3 (Reuters) -

* A nuclear reactor at EDF Energy's Hunterston B plant in Scotland will remain offline for safety checks, the UK's Office for Nuclear Regulation (ONR) said

* In March, ONR was informed that additional keyway root cracks had been found during recent planned inspections of the graphite bricks that make up the reactor's core

* The reactor was due to come back online this month but EDF (Swiss: EDF.SW - news) Energy has extended the outage until October, pending further assessment of the most recently identified keyway root cracks

* EDF (Paris: FR0010242511 - news) will require ONR's permission to restart the reactor, and ONR will assess the adequacy of EDF’s safety case for the longer term operation of the reactor, the regulator said (Reporting by Nina Chestney; editing by Jason Neely)