[Mr. Jeeves]

think it means it’s no longer in the corium ‘blob’ state but capable of traveling into the earth’s mantle in a stream-like state; which is much worse than any previous worst case scenario.

So vacationing to the Earth's mantle is no longer the safe family weekend getaway it used to be? :)

In all seriousness, it's time to retire the current generation of plants and move forward with thorium reactor technology. It really should have been done decades ago.

[HiTech RedNeck]

Once thinned out to a “stream” would it once more lose criticality and solidify again? Of course it still could chemically leach into the ground once there (oxides and such of uranium, plutonium etc.).