[Pistolshot]

In this dense medium, Schneider explained, light is slowed to three-fourths of its speed in a vacuum. In a nuclear reactor, charged particles flying off the radioactive rods through the water they are submerged in exceed this reduced speed. Because these particles contain an electric charge, they emit energy, called Cherenkov radiation. Any particles they bump into become radioactive, giving the water a characteristic blue glow.

I was referring to this explanation of how light moves in a dense medium. If there is energy being released in any kind of form, it is possible to use as fuel or an energy supply to convert to fuel. The Solar Sail is an idea, but what if you could use this extra 'energy' to help push the craft?

[PatrickHenry]

If there is energy being released in any kind of form, it is possible to use as fuel or an energy supply to convert to fuel.

You won't get more energy out of the system than you put into it. If you were putting in energy for some other purpose, then it might make sense to capture some of the wasted radiation -- if it were efficient to do so. But the whole system wouldn't be a net source of fuel.