[emiliobumachar]

Why can't they run the same water through the reactor again after the water cools?

[nrki]

Because it's highly radioactive.

[gambiting]

So? It's not like it's any worse at cooling because of it. After all, nearly all nuclear reactors use highly irradiated water for cooling in the first cooling loop.

[wheelerwj]

its not highly radioactive, its less radioactive than when it came out.