You are witnessing the startup of a small nuclear reactor, the blue glow you are seeing is due too electron particles produced in the fission reaction (splitting of the atom, in this case, the uranium235 isotope), the electrons leave the reactor core near the speed of light in water (225,000 kilometers per second) and once they hit the water they slow down to around 75% of their speed in the water, this interaction between the speeding electrons and the water produces blue photons or light parti