This rare photo was snapped by Reuters photographer Ruben Sprich during a yearly inspection of the Muehleberg nuclear power station in Switzerland. The cosmic blue glow is a result of Cherenkov radiation, an electromagnetic radiation seen in reactors.
In order to turn nuclear fission into electrical energy, nuclear power plant operators have to control the energy given off by the enriched uranium and allow it to heat water into steam. Enriched uranium typically is formed into inch-long (2.5-centimeter-long) pellets, each with approximately the same diameter as a dime. Next, the pellets are arranged into long rods, and the rods are collected together into bundles. The bundles are submerged in water inside a pressure vessel.