ENENews: AP: “‘China Syndrome’ predicted by US gov’t analysis — IAEA Expert: Pools of corium beneath reactors are up to 2 stories high”


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)
Published: March 30th, 2015 at 11:58 pm ET
By ENENews

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‘)


In From Enews: “US gov’t analysis says Fukushima is more serious than ‘China Syndrome’ — Destroyed reactors suffered worst type of containment failure”

US gov’t analysis says Fukushima is more serious than ‘China Syndrome’ — Destroyed reactors suffered worst type of containment failure (PHOTOS)

Published: October 8th, 2014 at 8:35 am ET
Email Articlehttp://enenews.com/govt-analysis-fukushima-serious-china-syndrome-worst-type-containment-failure-all-3-reactors

US Department of Energy, September 2013 (emphasis added): A severe earthquake and tsunami… caused significant damages on the reactors in Fukushima… [including] containment damage… and intensive radioactivity release… This paper reviews and compares a typical BWR SPAR Level 2 model with [what] occurred in Fukushima Daiichi Units 1, 2, and 3. It shows that the SPAR Level 2 model… could very reasonably describe the accident progression for a real and complicated nuclear accident… SPAR Level 2 model predicts that the containment integrity of Daiichi Units 1, 2, and 3 would be compromised by overpressure failure prior to or at core damage, which would be further impaired by drywell shell melt-through after vessel failure… The fission product release categories of Daiichi Units 1 to 3 are all classified as large early release in SPAR model… This work was sponsored by the NRC…

US Nuclear Regulatory Commission (NRC) on Early Releases (pdf): Generally, the most severe [containment] failure modes are ones that occur early in time (before or during reactor vessel failure) so that there is little settling or other retention of radionuclides in the containment… ruptures are more likely to lead to severe consequences… [T]he worst failures are failures that occur early and allow rapid, unscrubbed transit of radionuclides out of the containment…

NRC on Containment Failure Due to Drywell Shell Melt-through (pdf): There are two basic types of meltthrough to consider. First is the possibility of basemat meltthrough (the China Syndrome)… This failure mode is not generally catastrophic, because of the long time available for emergency response actions and the possibility of some retention in the soil.The second type of meltthrough is most applicable to Mark I BWR containments [All 3 Fukushima reactors used Mark I boiling water reactor containments]. In this case,molten material can exit the area beneath the reactor and flow across the floor, directly contacting the steel liner and causing it to fail. This type of failure… can happen much more quickly than basemat meltthrough and can lead to more serious consequences… A phenomenon of importance primarily for Mark I BWRs is shell (liner) meltthrough… The Mark I drywell floor area is small and the drywell shell is within ten feet of the pedestal doorway…

NRC on Containment Failure Due to Overpressure (pdf): Overpressure can theoretically lead to either leakage or large ruptureSteel containments are susceptible to rupture [if] the containment continues to pressurize. Given sufficient pressure, a crack in a steel containment can propagate catastrophically… a large rupture of the containment can lead to rapid transport of radionuclides to the environment with minimal retention.

NRC on Mark I BWR Containment Failure (pdf): [I]n general, Mark I containments are more likely to fail during a severe accident… However, the ranges of predicted failure probabilities are quite high for all BWR containment designs… BWR containment groups found a significant probability of early or late structural failure, given core damage.

See also: French Nuclear Experts: Did corium pierce steel liners of Fukushima reactors? How deep did it erode concrete? (VIDEO)

Published: October 8th, 2014 at 8:35 am ET
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