Nuclear Professor: Centuries before attempting any work on Fukushima molten fuel? — Concern over “potential phase separations” in corium

Published: November 13th, 2013 at 11:57 am ET
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Interactions between nuclear fuel and water at the Fukushima Daiichi Reactors, Professor Bernd Grambow, September 2013 (page 8):

[...] the actinides (probably >99.9%) were incorporated into the corium as the melt cooled and was quenched. The corium still contains these radionuclides, which leads to a very large long-term radiotoxicity of the molten reactor core. Access by water to the core may constitute an important vector for transfer of radioactivity. The challenge for radiochemists is to assess the long-term interactions between water and the mixture of corium and potentially still-existing unmelted fuel, particularly if the molten reactor core is left in place and covered with a sarcophagus for hundreds of years. [...]

Comparison of radionuclide release during the accident from the reactors with the radionuclide inventories remaining in the reactor and estimation of corium–water interaction from known spent fuel–water interaction provide important insight for developing assessment and management strategies for the molten fuel in the reactor cores. Furthermore, analyzing the radiochemical analyses of the temporal evolution of the radioactive elements in the cooling water of the accidental reactors provide valuable information on the chemical state of the corium and potential phase separations. Models for corium stability and for radionuclide release from corium upon contact with water will have to be developed [...]

See also: Japan Nuclear Engineer: I don't think they'll ever get Fukushima's melted cores; Will probably start covering reactors in concrete -- German Expert: May encase areas in sarcophagus

Published: November 13th, 2013 at 11:57 am ET
By

37 comments

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37 comments to Nuclear Professor: Centuries before attempting any work on Fukushima molten fuel? — Concern over “potential phase separations” in corium

  • Nick

    "developing assessment and management strategies for the molten fuel in the reactor cores."

    I am confident that some well meaning folks are doing just that.

    Unfortunately, the truth is, assessing and managing the molten fuel is impossible. Much of it is airborne. Much of it is perhaps spontaneously "dusting" off itself, interacting with water and air.

    We have massive computing power all over the planet. Amazing that NO ONE has an inkling of A: where the stuff is or B: what to do about it.

    Maybe our risk assessment strategies need a rethink.

    By the time we figure out where the coriums are the conclusion will be we can't do anything about it anyway.

    Which is pretty much where we are now anyway.

    Try to enjoy what you have today. Everything has changed. No wishful obfuscation will save us.

    but…"analyzing the radiochemical analyses of the temporal evolution of the radioactive elements in the cooling water of the accidental reactors provide valuable information on the chemical state of the corium and potential phase separations."

    Valuable information to whom? The sick children? The dying turtles? The melting starfish?


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  • Cisco Cisco

    Yea, let's build some more reactors, there's billions to me made before the buyers all succumb to Fuku's radiation and the lesson learned.

    What the hell, might as well die rich than the other alternative…providing value.


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  • weeman

    Now you know why at Chernobyl the Russians took great care that the corium was not immersed in water, for one it cools faster in air and restricts the migration of radiation to the water table, which makes it virtually impossible to recover and enhances its footprint, which would continually spread and disperse.


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    • mesa777

      I actually think this is where the Fukushima cores are at this point, in water somewhere under the plant. Satellite imagery over the plant has shown steam of some sort rising from the waters near the plant front. I assume without to much thinking here that these coriums have reached the h20 and now is rising into the water in the form of steam. This is a coverup in a very large scale as the US, Japanese goverments as well as TEPCO do not want to panic the populations. We are screwed, there is nothing man can do at this point but sit back and wait to see what happens. The clean up at Fukushima is all for show at this point as there is nothing anyone can do now…………… very depressing, just live life for today and not for the future.


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  • PhilipUpNorth PhilipUpNorth

    Dr. Grambow concludes: "Models for corium stability…will have to be developed".
    Here is one such model for consideration:
    Fission is still possible when nuclear fuel is in a state of corium melt. This can be seen in the more or less continuous releases of short half-life products of fission, such as Iodine-131, which indicate ongoing criticalities within corium at FDNPP. Instead of having continuously less decay heat, which is rapidly carried away by surrounding water, concrete, and steel of the nuclear plant containment vessel, ongoing fission increases the temperature of the corium mass, as it quickly eats its way through the bottom of the containment vessel, and through the base into the fill and bedrock underneath the plant building. The high levels of radiatiocontamination found in groundwater at FDNPP indicate that groundwater has come into direct contact with nuclear fuel debris in the ground underneath the buildings. The evidence is that one or more of the cores from Units1-3 have exited the reactor buildings, and are making their way into the earth, leaving behind highly radioactive corium lava tubes.
    Claims that corium from Units1-3 remain inside their containment vessels, coupled with the fact that the reactor buildings remain too hot for workers to enter, has been used as an excuse for inaction.
    Nor has there been any attempt to locate corium, which has escaped the reactor buildings.
    Nor has a plan been developed to mitigate the disaster.


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    • PhilipUpNorth PhilipUpNorth

      Meanwhile, the children of Japan are developing thyroid cancers at an alarming rate, for this early in the catastrophy, with far more bad news to follow.
      And the Pacific Ocean has begun to die.
      The people of the Earth must increase the pressure on TEPCO and Japan to come clean with the rest of the world on Fukushima.

      Where is the damn corium, eh, TEPCO? ;)


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  • moonshellblue moonshellblue

    Yes everything I've read says not to use water especially salt water which they have been using for reactor 4. Perhaps I'm mistaken but I thought I just read that TEPCO is using sea water to cool the SFP.


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    • razzz razzz

      Saltwater was only used as an emergency measure to cool ponds and cores until the end of March 2011. Scientists will be trying to figure out the implications (using saltwater) for a long time to come. Then there is the melts with tidal action causing saltwater intrusions continuing on a daily basis.


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  • ftlt

    In a few centuries, there will be many loose coriums spread about the planet..

    There won't be many non mutant humans left to worry about fixing them either..

    It is not just FUFU… The rate of failure of nuclear plants is clear and high… This failure rate will only worsen for manifold reasons going into the future.. There is no way to prevent their failure…

    Except one

    This one way to prevent future nuclear accidents is a way NOBODY in the industry or in state power will accept as a way out without a struggle..

    SHUT THEM ALL DOWN NOW!!!

    Live well not better..


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  • Lady M

    I'm showing some naivety here, but I'm really interested in knowing the answer to this question so here goes: We've heard several proposals that include sealing one or more of the Fukushima plants in concrete and leaving it untouched for at least a couple of centuries so the plant can, ostensibly, cool down. My question is: If a plant is sealed in concrete, that would remove the ability to cool it with pumped-in water. It would also prevent pumping in helium to prevent a hydrogen buildup and explosion. So, if we do create a concrete sarcophagus, wouldn't whatever is below the concrete (maybe a corium, maybe not, but definitely hot stuff) keep getting hotter and hotter and building up pressure (maybe steam, at least initially; maybe hydrogen; maybe something else) until the whole concrete structure exploded and rained down over a huge area as contaminated concrete dust? Please advise.


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    • We Not They Finally

      I'm not a scientist, but from all I've heard, the answers to your questions are yes, yes, yes, yes, yes, yes, and yes…. There does not seem to be anything suggested that anyone is actually clear would work. One of the more dire possible scenarios (Yoichi Shimatsu) is that it could lead to an underground volcano of pressure leading to the world's most giant "Boom!" And maybe no one can yet confirm it, but no one can discount it either…

      We are so f-cked.


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    • razzz razzz

      It is a work in progress since they have no idea where all the melts are plus the tidal action mixes saltwater with freshwater that flows around the melts which is much different than what goes on at Chernobyl with its above ground air cooling and radioactive dust being the main concern to keep contained. Daiichi, very little of anything is contained i.e. cooling waters, offgassing, dust from de-construction, saltwater intrusions, etc.

      Concreting over Daiichi's Units is a capitulation which doesn't address the groundwater intrusions. It only buys time on a hundred year scale to come back later and deal with it all the while the Pacific will be continually polluted with radioactivity flowing into it.

      It is getting to the point where radioactivity is being carried off by water and doesn't have a chance to build up in any one place. Capping melts still above the waterline involves water or air cooling (plumbing installations), monitoring (wiring), filtering, etc. There is still standing contaminated cooling water in lower parts of the Units that has to be removed yet. TEPCO/Japan doesn't tell anyone what is really going on at the site, that makes it difficult to even know the true current status.

      The envisioned ice wall is years away from knowing the result if it will function properly. The SFPs need to be unloaded not to mention Units 5&6 before any capping can take place or the threat of them tumbling down will remain. So sad.


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      • mesa777

        There is no way to concrete over the situation since the plant is located on a basically a beach front. These plant will eventually end up in the water uncontained, I would never swim in the pacific again, eat its seafood or be anywhere near the coast of Alaska, Western Canada and the Western United States to be exact. The radition number will increase for places like Seattle, Portland, Vancouver, god help us!! Who ever decided to place a nuclear power plant on a coast line should be placed in prison or made to volunteer to clean up the mess with a strong likely hood of passing away doing so…. G W


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    • PhilipUpNorth PhilipUpNorth

      Won't happen, in all likelihood making the answers to your questions no, no, no, no, and no, LadyM.
      Find and watch the video taken inside Chernobyl, walking around in the basement, looking at the "elephant's foot" of cooling corium coming out of a pipe. Impressive bit of film.
      It would be simple to plumb the sarcophagus to allow for pumping of water, helium, etc.
      Stoping the flowthru of groundwater would also be possible, as the foundation for the sarcophagus could be extended 100' deep, into the impermeable rock layer that forms the lower limit of the surface aquifer. Thus, all groundwater would be channeled around the foundation of the sarcophagus, and will flow into the ocean, without coming into contact with nuclear fuel debris left behind in the corium lava tubes.
      I doubt there is enough melted fuel left behind to heat up, or produce much hydrogen.
      The level of groundwater within the walls of the foundation can be regulated by pumping more water in, or pumping excess water out. Water could even be cooled, and recirculated back into the area within the walls of the foundation.
      Locating the corium from Units1-3 is job one, if a sarcophagus is to be built. If corium is found to be within the walls of the foundation, then some structure needs to be put in place to stop the corium from further movement. At Chernobyl, a tunnel was dug under the reactor building. The original plan was to circulate liquid nitrogen to freeze the core.


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  • TheBigPicture TheBigPicture

    N U C L E A R . . .

    Centuries to poison everything on the planet.


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  • Shaker1

    You know, it strikes me that a lot less modeling and a lot more physical labor would be more beneficial. Is that what we have with so many 'educated' people, that they can't see when shovels, torches, hammers, and real tools one holds in their hands is what's necessary? Believe me, I'm not ranting against knowledge, but knowledge without concrete action. The turbine buildings and all that stuff between the reactors that isn't necessary should be gone, dismantled and carted off. All those tunnels and exits for water should be sealed. This 'ice wall' idea (of which I've less faith than others because of the energy involved in its upkeep) would be a lot easier if they could create as small an area as possible for its use. Go ahead and model a shovel and see if it gets any work done. There should be people working like ants all over any unnecessary structure.

    I've run large projects with time-constaints. I don't drag my tool box over to do a project in which I need a hammer and a screwdriver. That's what pockets are for. One doesn't spend two hours in a meeting making a 15-minute operation more efficient. One doesn't allow the political crap to get in the way. There is no time to 'play nice'. The sense of urgency is lacking still. Pay them $80,000/yr, but get their ass on a shovel, or a backhoe, or on the business end of a hammer. They'd be more useful.

    It's been obvious since melting that the possibility of quick remediation was a dream. What's new?


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    • PhilipUpNorth PhilipUpNorth

      You are so right, Shaker1.
      The response of Japan and TEPCO to this disaster is orders of magnitude less than the situation demands.
      Right now, crews should be working on the Impermeable Wall (extended in a rectangle entirely around Units1-4), 24/7, with two crews working on each end of the wall, driving sheet steel pilings into the impermeable rock layer 100' deep. Ships should be lined up offshore to unload rebar, mobile concrete plants, cement, aggregate, and construction equipment. Work on a second Impermeable Wall should already be underway, 100' inside the first Impermeable Wall. The two Walls will be the inside and outside foundation forms. In the meantime, they can keep groundwater out of the construction site (and away from any corium under the plant buildings), as the fill and rock is excavated from between the two Impermeable Walls. Foundation concrete will be laid between the two Walls.
      The contents of SFP1-7 should already be in dry cask storage, or in the common SFP (CSFP). There is really no excuse for the delay on this task.
      The generator buildings, etc, should already be torn down and gone. (Instead, TEPCO hasn't even dealt with the water inside these buildings yet).


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  • Sol Man

    Not
    Until
    Causing to
    Leave
    Everything
    Around
    Radiated
    !


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  • Nick

    The con is that "oh we have always been radiated, it's part of nature, the earth itself is radioactive."

    What you don't hear, is how awful the man-made crap is.

    But the world will soon wake up. I am certain.

    Problem is, once enough people smell the s…h….t……fan, life as we know it will have changed irrevocably.

    That is why the silence of the MSM.

    It's game over.

    Heck, all nuclear waste is a forever horror.


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  • I think the article was saying that by anylising the water recirculated from the corium you might be able to determine state of corium. Maybe they do that but keep the results to themselves. With the right industry standard equipment you can anylize energy levels to identify isotopes and Im sure over the decades of nuclear knowlege say oh theres a lot of such and such present the corium must be doing this or that. They know what the melted cores are doing and where they are. Expensive but no brainer to stop groundwater flow upstream of site to save the Pacific. But first pay off the private bankers. O'Bummer smiles as he prattles on about whatever rhetorical flavor of the day is properly distracting. Dont look at the old white wizard behind the emerald curtain.


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  • Shaker1

    Yes, PhillipUpNorth, that harbor should be a damned busy place. I've already posted concerning those half-assed tanks. There could be a series of barges there now producing welded tanks and well as the concrete plants and for material accumulation and storage. I'm in a bad mood today, and can usually be a bit more calm about this, but it's just getting sick with all the talk and no action. The obvious may be painful, but talking it and yourself to death over it is accomplishing little. They're not even making the proper effort to clean up the area of non-contaminated useless articles and that stuff is just getting in the way of water control.

    It'd be nice to know where the coriums are, but I'd rather see effort made to contain the release of contaminants of which they know of the location, and know the mechanism or release where ever the source is. It's been my idea from the start that release and dilution were going to be part of the 'plan' (I just couldn't see an alternative after about 3/20) but this is getting stupendously silly.

    I've tried to get some balance in my life in my old age and ignore things I can't impact, but this is just getting too painful to watch. If shame was money, Japan would be awfully rich.


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    • maybesomeday

      Contrast TEPCO's approach with this Marine Corps General: "When the capture of an enemy position is necessary to winning a war, it is not within our province to evaluate the cost in money, time, equipment, or most of all, in human life. We are told what our objective is to be and we prepare to do the job." – General Smith (Iwo Island 1945)


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    • nedlifromvermont

      Hey Shaker1 … good posts, but hey now, it ain't only Japan, now is it? Have you heard, "Boo!" from GE? Global Exterminators? Who championed this jacked up submarine type power plant for large scale civilian nukes … when everyone around was asking, "What the Fuku?"

      Shame on GE for wreaking this havoc … for sowing seeds of our demise.

      Just like the PCB's in the Hudson or the Housatonic! Pollute. Deny. Obfuscate. Litigate. repeat.

      Six sigma my ass.

      peace …


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  • PurpleRain PurpleRain

    what does potential phase separation really mean in layman terms?


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    • Horse Horse

      phase separation analysis might suggest the current condition of the cores as in the sentence…

      "The microstructure of the solidified material shows two phases: (U,Zr)O2 and (Zr,U)O2. The zirconium-rich phase was found around the pores and on the grain boundaries and contains some iron and chromium in the form of oxides. This phase segregation suggests slow gradual cooling instead of fast quenching, estimated by the phase separation type to be between 3–72 hours.[14]

      The corium was formed in three phases.
      The first phase lasted only several seconds, with temperatures locally exceeding 2600 °C, when a zirconium-uranium-oxide melt formed from no more than 30% of the core. Examination of a hot particle shown a formation of Zr-U-O and UOx-Zr phases; the 0.9 mm thick niobium zircaloy cladding formed successive layers of UOx, UOx+Zr, Zr-U-O, metallic Zr(O), and zirconium dioxide. These phases were found individually or together in the hot particles dispersed from the core.[17]
      The second stage, lasting for six days, was characterized by interaction of the melt with silicate structural materials – sand, concrete, serpentinite. The molten mixture is enriched with silica and silicates.
      The third stage followed, when lamination of the fuel occurred and the melt broke through into the floors below and solidified there.[18]"

      http://en.wikipedia.org/wiki/Corium_(nuclear_reactor)

      …if they knew where the cores are we could know what they might do next.


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    • pattersonp

      The phase seperation is the different stages the corium took from going from cold fuel to being melted on the floor of the reactor buildings.

      Excellent info that basically proves the fuel is at corium ant not recoverable since you cannot re-bind the materials back together since the rods crack at 700'C… so 2000'C is mind boggling.

      It should be noted the Zirconium cladding reacted with the water to produce Hydrogen. The hydrogen blasts happened astleast 6 times on 1,2,3. There was also unknown blasts at 2, and probably elsewhere.


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  • mesa777

    Even if the three coriums are located there is not one thing that current technology can do to deal with them. I think that TEPCO, the US and Japanese governments already know the resting locations of the coriums however do not want to cause a panic by telling everyone that they currently rest in the water supply as this would just cause overall panic! Either way there is not much we can do about it. Hopefully the coriums are resting in the concrete bottom of the reactor buidlings simular to Chernobyl. The corium from Chernobyl is just resting on concrete however if its reached the water table who knows whats next.


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    • pattersonp

      They don't know where it is there either. The tomb is also collapsing so Chernobyl is definitely a bad example. That is still not under control and no corium recovered.

      If thats a lesson then whenever you read: fuel removal, 40 years de-comission, just switch the channel/website. They will never remove the fuel because its already corium and/or washing out to sea everyday.


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  • Heart of the Rose Heart of the Rose

    "Even if the three coriums are located there is not one thing that current technology can do to deal with them".

    Not a damn thing..point..snivel…


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  • Socrates

    Corium may be either an elephant's foot or a lava tube if it burns through the concrete.

    Ongoing fission would keep temperatures up for a century or two.

    Meanwhile, water will act as a vector of transport into groundwater and the sea.

    There is not much that can be done except to block uphill water flow.

    Water goes downhill. The sea will be the lowest point. The Pacific Ocean will become a radionuclide transport vector. They will study the chemistry of the effects of when corium meet the ocean. Marine biotoxicologists and oncologists will study the roadkill, which is us.

    What fools they were to risk every thing for a few decades of "cheap electricity."


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