CONCERN was growing last night after pictures emerged of widening cracks inside the nuclear reactor at Hunterston power station in Ayrshire.

It was known that the reactor, number three at the Hunterston B plant, had more than 370 cracks in its graphite fuel bricks that were found during routine inspections last year and which in turn led to the reactor being shut down.

READ MORE: Nuclear expert warns of Chernobyl-like disaster at Hunterston

Owners EDF Energy said the cracks were not widening any faster than expected – and that they were opening at a slower rate than models predicted – but that the number of cracks had grown.

They posted a video online and issued a letter to local people stating information about the inspection process.

The letter said: “When we take the reactor offline for an inspection the way we are able to identify keyway root cracking is by using specialist equipment to film and take measurements of the inside of the graphite fuel bricks.

“We do this by safely removing the fuel stringer from a channel then we pass a camera down the inside. Keyway root cracks are extremely narrow when they occur and this method allows us to observe very fine cracks, as small as 0.5mm wide; like the tip of a fine pen.”

EDF added that footage from the problem reactor “shows a crack that had an average width of 1.1mm at first inspection and has grown by around 1.8mm to 2.9mm wide.”

The plant’s director Colin Weir told BBC Scotland that the company would ask for the reactor to be restarted, saying: “Nuclear safety is our overriding priority and reactor three has been off for the year so that we can do further inspections.

“We’ve carried out one of our biggest ever inspection campaigns on reactor three; 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.”