The cores at Fukushima didn't "go into the ground" either. That doesn't prevent water in the core carrying radioactive material all over the place, once things are compromised.
True, but radioactive water is much easier to deal with than radioactive air because the hydrogen will capture the neutrons converting to Deuterium which is relatively safe and isotopes of oxygen are relatively shortlived. So as long as you can filter the heavy metals, it's in theory, less of a mess.
