Question

What is that smoke stuff that rises out of nuclear power plants? Is it pollution, and if so, what type of pollution? Or is it just steam?

Answer 1

Mostly steam.

Explanation:

Nuclear power plants need these big cooling towers to condense the steam back into water. The water then cycles back to the reactor to be heated up again, turned to steam and the steam drives a electrical generator. Most of what you see coming from these big towers is water vapour.