This article is more than 1 year old

This article is more than 1 year old

Footage has been released of cracks found inside a reactor at a nuclear plant in Scotland.

The unit at Hunterston B in North Ayrshire has not been operating after the cracks were found to be growing faster than expected.

In March last year a planned inspection of the graphite bricks that make up the core of reactor 3 uncovered new “keyway root cracks”. EDF Energy, which owns and operates the power station, said these have now grown to an average of 2mm wide.

The firm has released footage of the cracks, which was taken in 2017 and 2018.

The plant’s director Colin Weir told BBC Scotland: “Nuclear safety is our overriding priority and reactor 3 has been off for the year so that we can do further inspections.

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“We’ve carried out one of our biggest ever inspection campaigns on reactor 3; we’ve renewed our modelling, we’ve done experiments and tests and we’ve analysed all the data from this to produce our safety case that we will submit to the Office for Nuclear Regulation.

“We have to demonstrate that the reactor will always shut down and that it will shut down in an extreme seismic event.”

About 370 hairline cracks have been discovered, which means there is a fracture in roughly one in 10 bricks in the reactor core. Under current rules, operations must stop if the number of cracks exceeds 350.

The power station is one of seven in the UK using advanced gas-cooled (AGR) reactors switched on during the 1970s and 80s; there are 14 such reactors across the seven plants, several of which have seen their lifetimes extended into the 2020s.

• This article was amended on 12 March 2019 to clarify that advanced gas-cooled reactors total 14 in the seven UK power plants, and to correct a reference that called them “advanced gas-cooling reactors”.