It's not unheard of. Do you have info that this reactor is a boiling water type where the coolant steam is what turns the turbines? I didn't figure they'd use that setup. It's usually the radioactive coolant which is just circulated between the steam chamber and reactor rods, then a second coolant system is the one that gets boiled to create steam, to turn the turbines. If the system is the latter, there's always going to be one radioactive coolant and one not. Boiling of the radioactive one sucks. Hope that reactor case holds if it were to loose coolant and suffer a meltdown... Chernobyl's reactor did some crazy things with a 11 ft deep concrete slab over top of it....well, WAS over top of it.