By Susanna Twidale and Nina Chestney
LONDON (Reuters) - France's EDF (N:EDF) will begin decommissioning its Hunterston B nuclear power plant in Scotland by January 2022 at the latest, it said on Thursday.
The plant, which began operation in 1976, has two reactors, called 3 and 4, capable together of generating enough electricity to power around 1.7 million homes.
It had regulatory approval to operate until March 2023 but both reactors were taken offline in 2018 after cracks were found in the graphite bricks that form the reactor core.
"Given the age of the station and the desire to provide clarity for our staff and business partners, EDF has decided that Hunterston B will move into the defuelling phase no later than 7 January, 2022," EDF said in a statement.
Britain's nuclear regulator, the Office for Nuclear Regulation (ONR), on Thursday gave permission for reactor 3 to restart for six months after which time more checks will be carried out.
"We... have scrutinised the nature of the cracking observed in reactor 3 and are satisfied that it will not prevent the reactor from operating safely or impede its ability to be shut down if required during this period," said the ONR'S deputy chief inspector Donald Urquhart in a statement.
Such cracks happen when reactors age. This becomes a problem if it impedes the insertion of control rods or obstructs fuel channels within the reactor core which would affect the ability to shut down the reactor or cool the fuel, the ONR said.
Reactor 4 has been in operation for six months since its closure in 2018, but has not yet operated this year. EDF hopes to restart the reactor for a further 6 months from September, subject to approval.