Meltdown is hot news right now but what exactly is one, other than an event to be avoided at all costs? Some will remember the immense relief the world experienced when full meltdown was averted at Chernobyl and 3-Mile Island.
There has never been a full large-scale meltdown but this is the unknown situation that it describes: The overheated reactor fuel rods melt together and become as hot as the Sun’s surface – enough to boil iron into steam. The hot metal melts down through the concrete base of its containment vessel and then continues sinking into the earth below. Very little can stop the reaction at this point.
It doesn’t sink downwards forever, because when the hot molten fuel reaches the natural water table it will quickly turn the underground water to steam. We don’t know exactly what will happen then, having never experienced a meltdown or been crazy enough to test the idea out. But it is probable that the expansive steam would vent upwards with explosive force, carrying much of the radioactivity with it.
How high and far the radioactivity would disperse depends on the force of the blast from underground. It may settle in the surrounding area, or be carried by jet streams. Large amounts of radioactivity landing in the sea will eventually be carried by ocean currents throughout the world. If oceanic contamination continues through unchecked meltdown, it does not bode well for the world’s oceans, harbouring most of the life on planet Earth. On the plus side, fish may become too radioactive to harvest and find their numbers rebounding, albeit with more mutants.
The averted meltdown at Chernobyl involved one reactor. Four reactors are currently in danger at Fukushima and two more could become involved. This is a potential disaster such as we have never faced before.
Nuclear power is an answer to nothing.