Chernobyl's been having issues with cooling reactors. It got me thinking....

1 - What IS a nuclear reactor?
2 - Are there different types?

1 - A nuclear reactor is essentially a housing for a nuclear reaction to take place. There are 2 types of reactions. Fission and Fusion.

Fission is essentially the separation of atoms into smaller particles by slamming a neutron into an atom. This reaction creates energy.

Fusion is the action of combining atoms together creating a larger one. This creates a massively larger amount of energy vs. fission.

Although, from what I've seen, fission is what's used in reactors.

2 - Yes, there are different types of reactors. The ones I will be discussing are water-cooled.

Chernobyl's reactors are both RBMK (A graphite-moderated light water reactor) and VVER (Voda Voda Energo Reactor or Water Water Energetic Reactor).

Ukraine uses only VVER for their fleet of reactors currently. What do they all have in common?

Water.