The UK's nuclear energy regulator has given the go ahead for Reactor 4 at Hunterston to start back up.

The Office for Nuclear Regulation (ONR) today told the plant's owners EDR that it could return the reactor to service for 'a limited period of operation'.

EDF will be able to run the reactor for approximately six months, having been given permission for operation up to a total of '16.25 terawatt days'.

Last month the Herald reported that Hunterston is to close down earlier than expected after critical problems.

But the nuclear power plant plans to keep both Reactor 4 and 3 running for another year despite them having hundreds of cracks.

READ MORE: Hunterston nuclear power station to close down early after reactor problems

However, the ONR's assessment looked at whether cracking of the graphite bricks that form the reactor core could compromise fundamental nuclear safety requirements and inspectors were satisfied it could run for a limited period.

Donald Urquhart, ONR Deputy Chief Inspector, said: “In reaching this decision, ONR’s team of independent expert inspectors are committed to ensuring the safety of site workers, local residents and the wider public.

“We have scrutinised the safety justification and supporting evidence for this next period of operation in great detail, and I am satisfied that the high standards of nuclear safety that we expect have been demonstrated.

"We will only allow nuclear facilities to operate if we are satisfied that they are safe to do so.”

EDF had ploughed over £200m into repairing the plant's reactor with the aim of continuing to produce energy until 2023.

Hunterston B will now be decommissioned by January 2022.