[Liberty1970]

I would assume it evaporates from all the heat produced. That’s why they have to keep adding more.

[Fido969]

I would assume it evaporates from all the heat produced.

There has been some very good speculation in the threads here, based on the evidence we have so far, that the containment pools have cracked or are broken.

But all that means is that they will have to set up a flow of water, rather than just adding some water to 'top off" the system.