I think I was confused by news stories about situations where the reactor has failed in some way, and then there are stories of how radioactive water needs to be stored / disposed of somehow.
In those historical cases, the priority was cooling the core, the easiest method (especially if a substantial amount of plumbing is wrecked or questionable) is dumping water into it.
Which then becomes irradiated, and pools via gravity in any lower voids, and then eventually needs to be dealt with.
I think I was confused by news stories about situations where the reactor has failed in some way, and then there are stories of how radioactive water needs to be stored / disposed of somehow.