Here's what a nuclear reactor starting up looks like

Super neat video here that is identified as “Nuclear reactor starting up (TRIGA).”

Fairly sure there is science involved in this here stuff.

The blue light is from electrons moving through the water causing Cherenkov radiation.

Video: [Triga, Pulse operation, Nuclear reactor 240 MW, 7.12.2012]

“The reactor is brought to criticality and then the transient control rod is forced out. This causes a power pulse of about 500-1000 MW.”