GoPro footage catches eerie blue glow of a nuclear reactor

The heart of a nuclear reactor has been captured turning a piercing blue colour as it produces energy.
Footage of The Breazeale Nuclear Reactor, a research facility at Pennsylvania State University, was taken using a GoPro sunken deep within one of the plant's cooling tanks.
The eerie blue glow is created from Cherenkov radiation, a kind of electromagnetic radiation that occurs when a charged particle races through water faster than the speed of light.
A nuclear reactor splits atoms of uranium, a naturally radioactive element, to release energy.
The reactor's core sits in steel pressure tank so the water surrounding it remains liquid at temperatures of 460°C (860°F).
The footage shows the the underwater reactor as it is switched on and as it begins to operate at 500kW and then one MW.
As the reactor begins to work harder, the electric blue colour given off by the machine starts to intensify.
That's because as the plant produces more energy, more Cherenkov radiation is emitted.
The electromagnetic radiation appears a brilliant blue to the human eye as the reaction causes shorter wavelengths of light to become more intense.
But most Cherenkov radiation appears on an ultra-violet spectrum that is invisible to the human eye.