Reply #129: "Technically any fuel melting is a meltdown..."

[liberation]

Now the issue is wether it is the spare fuel rods that melted, or the core itself.

If the rods are melted, that is still a big issue because it would make the containment efforts to deal with the core really really difficult, due to the situation they create in the vicinity of the reactor. And an unattended reactor will eventually lead to a core meltdown. And a core meltdown is as catastrophic of a failure as can happen for a nuclear reactor. Yes there are several levels of "severity": it ranges from "we're pretty fucked" to "kiss your ass goodbye."

So this event is far from Three Mile Island...