So it turns out that nadinbrzezinski was correct re Fukushima

[AtheistCrusader]

475. If it melted into the ground under the plant, even 20 feet, the radioactive steam plume would

still be circling the planet on the trade winds. It would have hit the ground water table right under the plant.

It's still inside. It undoubtedly damaged the catchment, but it went less than 1/10th of the way through it, best guess based on the known energy involved. Same known quantity of energy that TEPCO used to calculate and inform the world that yes, in fact, the fuel payload HAD fully melted through the RPV back in June 2011, which was confirmed in this finding linked in the OP. (They went back and forth a couple times, in October they re-ran the numbers and thought it might still be in the six inch thick carbon steel RPV, but cooler heads prevailed, it melted through and landed in the catchment of the containment.)

Even the evidence that Gunderson over at 'fairewinds' posted showed no corium outside the containment, rather, radioactive sediment being washed out by the leaking coolant water, and settling in the torus room.

That's bad, but it's not 'ball of molten corium burrowing into the earth' bad.