so fun fact Tom, nuke stations like the one i work on (dungeness B) has two closed loops of water, the rods heat up Co2 gas that transfers its heat to a closed circuit of water that spins the turbines and then gets condensed with sea water, they never touch so the dirty water stays dirty and the sea water is always clean, dungeness actually has some very tropical like water right next to it due to the fact its just come out of the condenser units, may not be 100% with the workings of it all but the "waste" water is infact very warm, safe and mice to swim in!