/sci/ - Science & Math

I wonder if any nuclear physicists could help me on this. I'm reading an account of the Chernobyl disaster and in the section about the removal of water from the sections below the reactor there is a translated quote that experts at the time estimated that contact between the corium and water would have produced an explosion of 3-5Mt.

This doesn't really seem possible to me, apart from the inability of nuclear fuel to go prompt critical how would the water have even infiltrated the white hot fuel in the first place? I'm assuming they mean a steam explosion but then the 3-5Mt figure seems way to high. Equally, if they're talking about the amount of fallout generated as being equivalent to a 3-5Mt bomb, that seems far too low considering how much fuel there was (Total nuclear testing in the Pacific released tens of GBq while Chernobyl released EBq).

It's safe, stop asking questions, just like I'm a safe driver except for all those times I drove drunk, or was tired, or couldn't stop in time. Totally safe.

Since /g/ doesn't have enough knowledge I'll post the question here:

Why does the Chernobyl nuclear power plant have a chimney (pic related)? It's not a Soviet style cooling tower, those are located in the background.

Any ideas?