Fukushim Daiichi (Number One) has 6 reactors. Numbers 1 through 3 have partial or full core meltdowns.
#4 was empty, but had its fuel stored in the fuel storage tank – once you remove fuel from the nuclear reaction, it takes several years for the fuel to cool down so it doesn’t need additional cooling to avoid catching the zirconium cladding on fire. #4 is still a problem if it were to lose cooling of the fuel pool (which may be leaking)
#5 and #6 you probably forgot about. They were down for maintenance, but their fuel is still inside the reactor (with the nuclear reaction stopped). But that fuel continues to generate heat…. a lot of heat… This morning, the pump that is circulating sea water through the cooling loop failed. The temperature of the water got up to 96.3(C) – about 200(F). Had it gotten to the boiling point before the pump was replaced (it was), then the water would start to boil and potentially boil off the water inside the reactor we would have another core meltdown issue. Since it has been in cold shutdown for a while, it doesn’t heat up quite as fast – it took 15 hours to replace the pump. Fukushima is being hit by a typhoon today, which probably was related.