Monday Bites: Into The Blue

Into The Blue: Cherenkov Radiation. 

Credit: Idaho National Laboratory.
Public Domain, via Wikimedia Commons. 

Can you guess what you're seeing? Warp Drive? AMPS — Anti-Matter Propulsion System? Dark Matter Drive — it has to be. Nope. You're getting closer. What you see here seems to be future tech. At some point, it was. Not anymore. This is very much real. 

You're looking at the heart of a nuclear reactor; in this case, the core of the Advanced Test Reactor (ATR) at Idaho National Laboratory, Idaho, USA. See how it's so blue everywhere? That's Cherenkov Radiation, the unmistakable sign that the nuclear reactor is at full power. 

Unlike a commercial nuclear reactor (used for electric power generation), whose core is sealed shut, the ATR, a small-scale research reactor, involves an open-pool construction. In open-pool reactors, the reactor core, the central hub of all activity (literally), is kept underwater. Just like that. Owing to its certain peculiar properties, water happens to be the most efficient shield against ionizing radiation. Not only that, in these types of reactors, water also serves as a coolant to keep the heat of reactions in check and control the fission of uranium. A nuclear reactor is powered up in stages. In the beginning, a faintly (of a Prussian shade) bluish glow lights up below deck — that's when you know that atoms have started to split. At full power, the faint luminance transitions into an intense shade of brilliant blue (sometimes violet). This is Cherenkov radiation, named after its discoverer and winner of the 1958 Nobel Prize in Physics for the same, Pavel Cherenkov. 

Cherenkov radiation is analogous to a sonic boom. When an aircraft breaks through the sound barrier, cruising faster at 343 meters per second (1234 kilometers per hour or 767 miles per hour) — the speed of sound in air, an ear-piercing noise, a boom trails along the receding aircraft. At the same time, a white skirt (air condensing into water droplets) drapes the aircraft's stern. The speed of light is a constant in vacuum, 300,000 km/s or 186,000 miles per second. In water, light slows down to 75% of its maximum speed. Protons and electrons — necessary by-products of nuclear fission, when they don't slow down much, end up traveling faster than the speed of light in water. Mimicking a supersonic aircraft carrier, these charged particles set off a shockwave. Cherenkov radiation is a shockwave of light!