STATION bosses have welcomed a decision by nuclear regulators to allow reactor 4 of Hunterston B to be switched back on - after it was found it could still withstand an earthquake.

The Office for Nuclear Regulation (ONR) say Reactor 4 at Hunterston B power station is safe to return to service for approximately six months.

ONR’s assessment focussed on whether cracking observed in the graphite bricks that form the reactor core could compromise its fundamental nuclear safety requirements.

They found unimpeded insertion of control rods and unimpeded movement of fuel; ensuring that gas flow will be maintained to ensure cooling; and that appropriate moderation (slowing neutrons to sustain the nuclear chain reaction) and thermal inertia (reducing the speed of temperature changes) are maintained.

Specialist ONR inspectors have concluded that an adequate safety justification had been provided, and can be safely shutdown, even including in a 'significant seismic event'.

Hunterston B station director Paul Forrest said: “I welcome the ONR’s decision to approve the restart of Hunterston B power station’s other reactor.

"Having both reactors back online will mean that Hunterston B can continue the important job of making low carbon electricity and help reduce reliance on gas-powered generation until the site moves into defuelling by January 2022."

EDF has decided that Hunterston B will move into the defuelling phase no later than 7 January 2022. This is subject to a further inspection in spring 2021 and then regulatory approval for a final 6 months of operation.