Quote from newguy05:
To be a disaster, the plant(s) need to have a full meltdown, then the container designed to withstand the resulting blast needs to fail, then shit will be flying all over the place. Partial meltdown doesnt do much, even a full meltdown wont matter if it's contained within the plant.
Chances for that to happen is pretty low, it will be a blackswan within a blackswan. I think they are pumping sea water or something into the plants now to try to cool it which sounds pretty desperate but still it's a low probability you will have a full meltdown and the containment specifically designed for it fails...