Has Fukushima Daiichi Reactor 2 Core Melted Down?

It is said that it is physically impossible for the nuclear material in any of the Fukushima reactors to melt through the containment vessels. Despite a rumor of a crack in one of the vessels, nuclear power experts have maintained that it is impossible that there could be such a crack. Nonetheless, a US based GE-connected nuclear engineered who has ties to the Fukushima facility has boldly asserted that he thinks that the core in reactor 2 has “melted through the bottom of the pressure vessel … and at least some of it is down on the floor of the drywell.”

Richard Lahey was head of safety research for this kind of reactor for GE at the time that they installed the units at Fukushima. He has told his analysis to The Guardian. You can read it here.

NHK news service has not mentioned this, nor has the International Atomic Energy Agency. This is utterly unconfirmed and probably not true. It is, after all, impossible.

But if it is true, this places the situation at Fukushima on the high side of the TMI tickmark on the scale of badosity. The core at Three Mile island got all messed up but it did not breach its containment.

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19 thoughts on “Has Fukushima Daiichi Reactor 2 Core Melted Down?

  1. Greg, I agree that this is worse than TMI, quite a bit worse now. But, it is now a couple of weeks on, and the fuel is a lot cooler than it was. The fuel melting requires ~2700 C. That is almost white hot. Something that hot radiates a lot of energy. If the fuel has not melted, then it remains in pellets which have some void fraction through which water can flow, dissipating heat by convection and evaporation. There may be â??bumpingâ?, where the fuel collapses into a pile, the water inside the pile boils and the pile gets propelled up. This would be bad because it would grind the fuel up into smaller bits.

    If the containment well is filled with water, when the fuel tries to melt its way through the steel reactor vessel, it will contact water which will boil and dissipate heat.

    What the Japanese government should do is nationalize the utility because it now has debts that exceed its assets and take over the operation. Lay pipe with double walls so that any leaks would be contained to places off site where they can make big tanks that have double walls, and shielding so the contaminated water can be pumped off site and stored until it can be processed.

    I think the priority should be on getting as much radioactivity off site as can be safely gotten off site. As much spent fuel as is intact and can be gotten off site should be gotten off site.

  2. Chernobyl was entombed, Fukushima will be buried at sea. Reactor 2’s core has been eroding into the Pacific Ocean for nearly two weeks.


  3. By “off site”, I mean a few hundred meters away. Then set up a system to separate the H2O from everything else. Reuse the water for cooling and cleaning up the reactor.

  4. “The fuel melting requires ~2700 C”

    Uranium oxide and zircalloy form an eutectic mixture which melts at 1200C. This requires heavy deformation of fuel rods, though.

  5. Daedelus: “Greg, I agree that this is worse than TMI, quite a bit worse now. But, it is now a couple of weeks on, and the fuel is a lot cooler than it was.”

    My God, man, you’re right! What was I thinking? Really, what led me to think there was an ongoing concern here?

    Daedelus, that horse left the barn 10 days ago. Multiple meltdowns have occurred (review the comments from yesterday, if you have any interest, where I quoted the Japanese nuclear safety official– the presence of plutonium identifiably from a Daiichi reactor, from samples now a week old, says that the temperatures were sufficient for meltdown, and containment was lost… wait for it.. *over a week ago*).

    For someone obviously bright and informed, your generosity to Tokyo Electric and the Japanese government is truly stunning.

    Returning instead from the land of idealized abstractions to the horrific scene unfolding in reality:

    (from: http://www.japannewstoday.com/?tag=fukushima-nuclear-meltdown)

    Contaminated Seawater 3,335 Times Normal Detected Close to Fukushima Nuclear Plant

    “Outside the damaged nuclear power plant in Fukushima Japan 3,335 times the normal amount of radioactive iodine has been detected. This is the highest rate yet despite Japanese officials having made statements claiming no contaminated water was confirmed to have flowed in to the ocean from trenches close to the damaged nuclear reactors.”

    (from: http://www.nytimes.com/2011/03/29/world/asia/29safety.html)

    Cesium 137 levels were 20 times the normal level about 1,000 feet from the effluent at the Fukushima Daiichi nuclear power plant. That is far less than the level of the other main radioactive isotope spilling from the plant, iodine 131. It was found in concentrations of more than 1,150 times the maximum allowable for a seawater sample a mile north of the plant.

    Still, scientists say, cesium 137 poses the greater long-term danger to the marine food chain. Iodine 131 degrades relatively fast, becoming half as potent every eight days. So the radioactive risk can be combated by banning fishing and the consumption of seafood for a period of time, as the Japanese have already done.

    Cesium 137, on the other hand, has a half-life of 30 years. Worse still, it is absorbed by marine plants, which are eaten by fish and â?? like mercury â?? tends to become concentrated as it moves up the food chain.

    â??Itâ??s worrisome in that CS 137 is leaking, although the levels are still low,â? said Paul G. Falkowski, a professor at Rutgers Universityâ??s Institute of Marine and Coastal Sciences. â??At some point this water that is pooling in various places is ultimately going to make its way out to the sea.â? And if there is a lot of cesium 137 over an extended period â??then youâ??ll have to worry.â?

    (from: http://www.theepochtimes.com/n2/world/impact-of-radiation-on-ocean-water-may-be-seen-in-long-term-53808.html)

    “Although the effects of radioactive elements in the ocean may not be immediately observable, the size of the ocean should not be viewed as sufficient to dilute the radioactive waste.

    â??The vastness of the ocean is often taken to mean that it has an enormous power to dilute most of manâ??s wastes. That is a misconception that led most nuclear powers to dump radioactive waste into the ocean, before doing so was banned by international treaty in the 1970s,â? wrote Jacob Hamblin via e-mail. Hamblin teaches history of science at Oregon State University and has researched and written about the history of dumping nuclear waste in the ocean.
    One of the big issues is that experts donâ??t know exactly how the different radioactive materials travel through various water systems.

    â??Scientists do not have a firm grasp of the pathways of these isotopes in every given environment. Each sea, bay, and estuary is different,â? according to Hamblin.â?

    Daedelus, it really is much worse than you’ll be willing to even imagine, let alone acknowledge, I expect.

  6. For someone obviously bright and informed, your generosity to Tokyo Electric and the Japanese government is truly stunning.

    A thought I keep returning to: a great many people were very sceptical of the information BP put out about the Deepwater Horizon blowout, but for some reason I haven’t seen anything like the same level of scepticism displayed towards information put out by TEPCO about Fukushima. Maybe I’m just reading the wrong blogs… Or maybe radionuclides just aren’t as obvious as a fucking massive oil slick. Also, TEPCO haven’t been dumb enough to hook up live public webcams…

  7. Hereâ??s what weâ??re talking about.

    Water used to try and cool the reactors and spent fuel has entered the soil and ground water. Most of it. Because the issue is not simply runoff, but the condition of the substructure and soil beneath the reactors. It is unreasonable to assume that the structures remained largely intact following the earthquake, even before the tsunami hit. Why?



    â??The magnitude scale is really comparing amplitudes of waves on a seismogram, not the STRENGTH (energy) of the quakes. So, a magnitude 8.7 is 794 times bigger than a 5.8 quake as measured on seismograms, but the 8.7 quake is about 23,000 times STRONGER than the 5.8! Since it is really the energy or strength that knocks down buildings, this is really the more important comparison. This means that it would take about 23,000 quakes of magnitude 5.8 to equal the energy released by one magnitude 8.7 event.

    (If my calculator (from the USGS) is correct, the 9.0 Sendai earthquake released 1412.537 times as much force as the 6.9 Kobe earthquake.)

    (from: http://www.ce.washington.edu/~liquefaction/html/quakes/kobe/kobe.html)

    â??The spectacular collapse of the Hanshin expressway illustrates the effects of the high loads that were imposed on structures in the area. The strong ground motions that led to collapse of the Hanshin Express way also caused severe liquefaction damage to port and wharf facilities as can be seen to the left and below…

    When liquefaction occurs, the strength of the soil decreases and, the ability of a soil deposit to support foundations for buildings and bridges is reduced as seen in the photo of the overturned apartment complex buildings in Niigata in 1964.

    Liquefied soil also exerts higher pressure on retaining walls, which can cause them to tilt or slide. This movement can cause settlement of the retained soil and destruction of structures on the ground surface�

    These were concrete and steel structures designed to be earthquake resistant. They crumbled like crackers.
    Interesting reading from Japanese seismologists on using probabilistic models to estimate earthquake ground motion intensity (from 2007):


    Note the highest magnitude they considered, based on 50 and 150 year estimated occurrences, was 7.2.

    None of the load estimates for any nuclear reactor, anywhere, accounted for a 9.0 earthquake. Why assume that there arenâ??t fissures in both the structure of the reactor buildings, and in the soils beneath? Because the land and buildings of Daiichi somehow acted differently, miraculously, than any other structure in any other earthquake?

    Talk about favorable assumptions.

    Why are we seeing radiation spikes in seawater? Because the materials are percolating through the soil, which has become more permeable from the effects of the earthquake, especially liquefaction.

    As I mentioned in a comment to Greg several days agoâ??the aquifer is the ballgame.

    The tunnels are only the beginning of the problem with water at Daiichi. Letâ??s not forget that there are 10 times the amount of radioactive materials at Daiichi than were kept at Chernobyl.

    How will this play out in the long term?:

    (from: http://books.google.com/books?id=eEB6-exO8bQC&pg=PA3&lpg=PA3&dq=percolation+of+radionuclides+through+soil&source=bl&ots=p1dDiiZspH&sig=2CP32rQsx5FZnM1qJ6KbVQSrGtw&hl=en&ei=jEGTTa0b5b_RAfHX5MwH&sa=X&oi=book_result&ct=result&resnum=9&sqi=2&ved=0CE4Q6AEwCA#v=onepage&q&f=false)

    â??The behaviors of radioactive material dumped in the Irish Sea from Sellafield and now finding its way ashore again is worrying government ecologistsâ?¦

    â?¦much of the waste has been absorbed onto the deposits of fine sediments offshoreâ?¦

    This sediment now serves as a reservoir of radioactive material that is deposited in several Cumbrian estuariesâ?¦
    The extreme variability of concentrations of radionuclides being found in plants and animals is also setting serious problems for ecologists. The range of concentrations being discovered is â??two orders of magnitude greater than in normal biological processesâ?? .â?

    Thatâ??s 40 years down the pike folks. This is where the best thinking, estimates and favorable assumptions of nuclear engineers have gotten us in Daiichi.

    Maybe itâ??s time to stop going to that well, to stop relying on nuclear engineersâ?? best thinking. The history suggests that thinking consistently sucks.

    I really do hope nuclear advocates wake up to this.

  8. Greg, melting is quite different than breaking apart. In TMI, the melting occurred very early, on the first day.

    Only if the fuel melts is it likely to form a hypercritical assembly. I think it would take a hypercritical assembly to generate enough energy fast enough to breach the remains of the reactor vessel and the containment building.

    The situation is plenty bad enough, it still could get a lot worse but it probably won’t.

    Seawater has about 2 ppb Cs in it. In a cubic km, that is about 2 tons. There are ways to remove the Cs137 before letting water discharge into the sea. Clinoptilite will take Cs out of fresh water, seawater not so much. Clinoptilite is a natural zeolite available by the thousands of tons in the US southwest.

  9. phillydoug, according to the design of the Fukushima facility, they went down to bedrock. The facility isn’t built on soil.

    The Fukushima reactor is built right on the coast. The ground water at the Fukushima reactor flows out to sea.

    Usually concrete is not considered to be a liquid-proof barrier because concrete often cracks. Usually there is some other type of liquid-impermeable membrane. They are planning to seal the entire surface in and around the Fukushima reactor with epoxy. That will prevent rain from flowing through the soil.

  10. Daedalus: “they went down to bedrock. The facility isn’t built on soil.”

    Good to know– and to you that means they excavated all the top soil in every direction for a mile down to bedrock, and back filled with concrete?

    Or, they put the sub-structure onto bedrock, and back filled with soil, much like construction at any other large site– hence the ‘soil samples’ taken around the site.

    Gotta say, I don’t think your response in any way addresses anything I suggested about the effects of the earthquake on the structure of the reactor buildings (including multiple fissures in both the sturctures, the subsurface soil around the site, and yes, the bedrock itself (following the 9.0 jolt), or the geophysical characteristics of the site (and under it)– especially with the effects of liquefaction. In other words, I think you simply dodged the issues that might disturb the placid surface too much.

    “Usually there is some other type of liquid-impermeable membrane. They are planning to seal the entire surface in and around the Fukushima reactor with epoxy. That will prevent rain from flowing through the soil.”

    Just keep that optimism, Daedalus.

    For the rest of us:

    (from: http://www.guardian.co.uk/world/2011/mar/29/japan-lost-race-save-nuclear-reactor)

    “At least part of the molten core, which includes melted fuel rods and zirconium alloy cladding, seemed to have sunk through the steel “lower head” of the pressure vessel around reactor two, Lahey said.

    “The indications we have, from the reactor to radiation readings and the materials they are seeing, suggest that the core has melted through the bottom of the pressure vessel in unit two, and at least some of it is down on the floor of the drywell,” Lahey said. “I hope I am wrong, but that is certainly what the evidence is pointing towards.”

    The major concern when molten fuel breaches a containment vessel is that it reacts with the concrete floor of the drywell underneath, releasing radioactive gases into the surrounding area. At Fukushima, the drywell has been flooded with seawater, which will cool any molten fuel that escapes from the reactor and reduce the amount of radioactive gas released.

    Lahey said: “It won’t come out as one big glob; it’ll come out like lava, and that is good because it’s easier to cool.”

    The drywell is surrounded by a secondary steel-and-concrete structure designed to keep radioactive material from escaping into the environment. But an earlier hydrogen explosion at the reactor may have damaged this.”

    No fabric above or below Daiichi is going to do a damn thing about what’s happening there.

    By the way, slight tangent, maybe relevant– in my home state of Pennsylvania, there’s been a growing ruckus about the use of ‘fracking’ (using pressurized fluids to fracture shale, in order to get at natural gas deposits). Funny thing, cracking the rocks and introducing fluids resulted in flammable drinking water in water wells dozens of miles away. Seems the engineers were confident that the overal structure of the bedrock would ‘contain’ and hazardous fluids from the fracking process. But there you have it.

    So, Daedalus, you were saying about the confidence you have in the interity of the bedrock and that fluid stopping membrane under the concerete at Daiichi?

  11. Hey, Daedalus– actual hydrogeological study of Fukushima prefecture. How about that? ‘Clay-loam soil’. ‘relatively high water content’. Who knew?

    But Daiichi is on bedrock, and has a water-proof membrane, so it’s all ok.

    (from: http://cipa.icomos.org/text%20files/KYOTO/129.pdf)

    “Field study of resistivity image profiling method was carried out at Miyahata site located in Fukushima Prefecture. Result of resistivity distribution was investigated with the result obtained from soil boring. From the result of resistivity image profiling method, it could be estimated that Miyahata site was mainly consists of clay-loam soil and their water content were relatively high because low resistivity area was distributed throughout the remains.”

  12. I am not sure why you linked to that paper. According to it, the soil is unsaturated. Unsaturated soils are almost never subject to liquefaction by ground motion.

  13. Daedalus,

    I’ll give you this– you’re consistent.

    You can always be relied on to base an argument on an idealized abstraction, because, you know, we wouldn’t want to make things confusing with actual observations and data, would we?:


    “Thanks to Alessandro I came across this incredible video of liquefaction occuring in the Tokyo Central Park during the M9.0 Japan earthquake. We can see a lot of very interesting features. First, cracks are opening, perfectly visible on the paved road and the cobble. Then we see the differential moving along those cracks, they are widening and narrowing and thereâ??s vertical movement as well. Soon, the first ruptures appear in the meadows, despite the soft sediment there.”

    Funny thing, I don’t recall Tokyo central park being noted for it’s unusually high and continuous saturation levels. Ah, whatever, that’s what I say.

    Anyway, back to theory– specifically those factors that might increase the risk of liquefaction (interstingly, soil saturation– before the seismic event– doesn’t seem to make the list):

    (from: http://www.ceers.org/ijest/issues/full/v6/n2/602017.pdf)

    Sediment properties (lithology, age of deposit, grain size and shape and deposit compactness) and
    hydrogeological conditions (groundwater level) make the site favorable for seismic wave amplification.
    Consequently, this makes the soil prone to liquefaction upon seismic shaking (Stephen et al., 2004).
    In this case, where coarse silty, sandy soil and shallow groundwater level are present, long duration
    of strong earthquake tends to increase soil liquefaction potential (Ozdemir and Ince, 2004).

    (from: http://mahabghodss.net/NewBooks/www/web/digital/nashrieh/Engineering%20geology/VOL.76/VOL.76,%20%20ISSUES%203-4,%20JANUARY%202005/5/Field%20occurrences%20of%20liquefaction-induced%20features-%20a%20primer%20for%20engineering%20geologic%20analysis%20of%20paleoseismic%20shaking.pdf)

    “In general, if the water table is on the order of 10 m or more below the ground surface, the formation of liquefaction features (due to level-ground liquefaction) from any failure mechanism is highly unlikely, unless shaking is severe and the field setting is conducive to their formation.”

    So, why did I give the prior link? Because it described the soil properties around Fukushima. Clay-sand mix. Low tensile strength.

    Any other features relevant to liquefaction? Take a guess how deep the water table is around Fukushima (being on the coast and all).

    And just how strong was that quake?

    But let’s end where we began– why bring up liquefaction? Because it was observed to occur– during the quake.

    Were there liquefaction effects at Daiichi? High likelihood, considering all the factors geologists and seismologists seem to think are important. (pre-quake saturation not seeming to rate highly with anyone but you, Daedalus).

    You really might want to put your theoretical framework thorugh the wash spin cycle a few times.

    And when you’re ready, please feel free to address any of the concerns I raised about the effects of the earthquake, including liquefaction, on the integrity of the structure of the containment buildings, and the opening of pathways for contaminated water to percolate through the soil and aquifer. Which you still haven’t. Perhaps that’s a little too uncomfortable to actually tackle.

  14. Stop it Japan.Save our world.The whole world is deceived by Japan.

    The Japanese army made a false video.

    The hole which does not exist is photographed.

    There was no hole in the center of UNIT1-4 before explosion.

    Exclude UNIT2 after UNIT1 explosion.

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