A PWR nuclear reactor waste water for the condenser is two stages away from water that is heated by fuel rods, so not even remotely a problem. A BWR condenses steam that was directly boiled with nuclear fuel, but the condenser operates at lower pressure so if there is a leak, water from outside goes into it, rather than getting pushed out. Source: Tour of the decommissioned Barsebäck power plant. They still run tours but don't know how much you would be able to film.