Doesn't nuclear need water?

Answer

Just like coal plants, nuclear power plants require cooling water. The majority of water is withdrawn and then released back into the original water source which could be an ocean, river or lake. Since the water required for cooling is circulated through a seperate loop to the reactor it does not become radioactive. If water is scarce, nuclear power plants can use treated waste water or dry cooling.

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File:PressurizedWaterReactor.gif - Wikipedia

Pressurised Water Reactor Animated Diagram