That's what I've been saying for three days. It doesn't make sense that they can't keep any water in. Sure, there's steam that's escaping but there's much more going on that's causing the no water situation. The generator/pump problem just doesn't ring true. First they couldn't keep water in the container whatever and now there's water problems in the pools. Water doesn't just get up and jump out of the pools so the only other way out is down through a crack in the foundation.
These aren't just hot bars of steel like you'd find in a blacksmith shop, that spit off a bit of steam when you throw them in the water. They are actually creating an amount of heat that's hard to understand in the context of everyday life.
Freshly-spent fuel can generate up to about 13 watts of heat per kilogram of uranium, and one rod is about 6 kilograms, and a single fuel assembly contains about 95 rods. So that's nearly 7,500 watts of heat, or about 25,000 BTU per hour, in a single fuel assembly, out of hundreds and hundreds used in the reactor core. And that's AFTER they're used up.
Just three assemblies would be roughly equivalent to the furnace in my home running non-stop 24x7 for year after year. It's hard to imagine that there's that much energy in such a small amount of material, but there is. God works in mysterious ways.
So you can see why the water they're sitting in would heat up and evaporate in a hurry.