AP: Melted fuel may have “dropped even beyond” the bottom of Fukushima plant — ‘China Syndrome’ predicted by US gov’t analysis — IAEA Expert: Pools of corium beneath reactors are up to 2 stories high (VIDEO)

AP, Mar 27, 2015 (emphasis added): [It] was billed as a way to decipher where, exactly, the morass of nuclear fuel might sit at the bottom of reactors… But what went wrong, even in a simple demonstration for reporters… was a sobering reminder of the enormous challenges that lie ahead… a programming glitch could not be fixed in time for Friday’s demonstration… No one knows where the molten fuel debris lies, and in what shape or state. [TEPCO] has said it likely sank to the bottom of the plant. But the fuel could have dropped even beyond. Tadashi Yotsuyanagi, an official in charge of the muon project at Toshiba… acknowledged the technology will not be able to get the complete image toward the bottom of the reactor… David Ireland, a professor who heads the Nuclear Physics Group at the University of Glasgow, said muons may be the only way to probe inside atomic reactors. “There are not really any other noninvasive options that will allow inspection,” he said in an email.
The Japan Times published the AP report above, however one sentence was altered. “Tepco has said it likely sank to the bottom of the plant. But the fuel could have dropped even beyond” vs. “But the fuel could possibly have escaped even beyond the containment facility to the outside environment.”
IAEA technical meeting Managing the Unexpected, Harri Tuomisto, Sr. Nuclear Safety Officer at Finland’s Fortum Power, 2012:

• Part 4: “If the cooling is not successful, it means the corium melts through the vessel… When this massive amount of corium enters into the containment zone, there are very, very many different energetic consequences… Interaction of molten core and concrete starts… concrete is eroding, and this eroding of concrete, for a long time it was known as China Syndrome.”
• Part 5: “The corium will be in 3 parts, there is a solid crust formation in the bottom of the pool, then there’s a pool of oxidic materials… The metals and oxides are not soluble with each other and the metals will be separated… which is bad news in the sense that the heat transfer to the vessel is much higher, and it’s much more difficult to guarantee the integrity of the [containment] vessel in that case.”
• Part 6: “Molten corium on the containment floor, it’s eroding the concrete and going partially downward. Actually it will never go to China, because it also erodes sideways… The final size of the pooling maximum case is 10 to 15 meters in diameter, and 6-7 meters [20-23 ft or 2 stories] deep — or even deeper.”
• Part 9: “There are quite many challenges… There are different energetic phenomenon… which can lead to different combustions… accelerating flames, or even detonations — which can cause a very high pressure in the containment and even break the containment… Then there’s this China Syndrome — attack of containment liner by corium — which can also bypass containment.” (See US gov’t analysis: Fukushima containment breached due to “failure of the drywell liner by melt-attack“)
• Slides 3-4: If corium melts through the vessel, there are various energetic consequences caused by ejected high-temperature molten corium… Molten corium on the containment basemat initiates core-concrete interaction that releases aerosols and non-condensible gases to containment atmosphere and erodes the concrete (‘China syndrome‘)

Watch the IAEA presentation here