Video footage from inside one of the reactors at a nuclear power station in Scotland has revealed over 350 hairline cracks in the bricks, meaning it may make it impossible to shut down in an emergency.

Electrical Company EDF, who owns the Hunterston B power station in the Scottish county of Ayrshire, roughly 40 kilometers (24 miles) from Glasgow, released images and footage that shows cracks have formed inside the reactor’s graphite bricks, which are used in the core of nuclear reactors to slow down neutrons and keep the reaction stable. The bricks are also used to channel the carbon dioxide used to cool down the reaction. For this reason, they play an important part in making the facility safe.

Cracks are expected to happen over time, and given that the station was built in the 1970s, it's not surprising. However, last year, the power company discovered that Reactor 3 had 370 hairline cracks in the roughly 3,000 bricks in the reactor – the safety limit is 350 – so the reactor was taken out of operation and has not produced electricity for a year. The limit, put in place by the Office of Nuclear Regulation (ONR), is to guarantee that the reactor can be shut down safely in an emergency.

"We have to demonstrate that the reactor will always shut down and that it will shut down in an extreme seismic event," station director Colin Weir told the BBC. "We've carried out one of our biggest ever inspection campaigns on reactor three, we've renewed our modeling, we've done experiments and tests and we've analyzed all the data from this to produce our safety case that we will submit to the ONR.”

EDF is planning to make a case to the ONR that the operational limit should be raised to 700 cracks and then restart the reactor. All 14 Advanced Gas-Cooled reactors in the UK employ graphite bricks, so the decision made about the crack limit in this reactor may affect the wider energy production of the entire country. There is clearly a lot of interest in understanding graphite and its safety limits in detail.

"Putting a specific value on the number of cracks considered reasonable is difficult. Graphite is complicated, and irradiated graphite is more so. This is why scientists have been lately doing so much research on it," nuclear expert Dr Ben Britton from Imperial College London told IFLScience. "Typically limits were based upon very conservative estimates, and EDF will have to make a rigorous technical case for ONR to approve changes to the limit."

Currently, the Hunterston B power plant provides a base-load of electricity enough to power 1.8 million homes and it is expected to remain in operation until 2023.

[H/T: BBC News]