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Fukushima: spent fuel pools & Hiroaki Koide

  1. Apr 19, 2012 #1
    Dear forum members,

    I live in Japan and some of my friends got recently quite worried after watching this video: http://www.youtube.com/watch?feature=player_embedded&v=eJi-o4F8eOo
    It shows an interview with Dr. Hiroaki Koide, talking about the possible consequences of the collapse of the spent fuel storage pool in Fukushima Daiichi.
    I am not a physicist myself, so I would like to ask the specialists here in the forum to comment on the video. I am not expecting a simple answer like "he is right" or "he is wrong", but more looking for an informed insight into why what he saying might be right or wrong.

    Thank you all!
  2. jcsd
  3. Apr 19, 2012 #2

    jim hardy

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    Nobody has responded yet ?

    Here in USA we use a term "Spin" to denote how objectively a news story is reported.
    A completely honest report that does not reflect the reporter's opinions or interpretation would be "no spin".

    "Spin" usually employs emotional appeals instead of logical ones.

    I watched that video twice. I believe it is "Spun" to achieve a political goal of shutting down nuclear power plants in Japan.

    To that end they correctly reported that the spent fuel contains lots of radioactive material. And that, should the pool run dry, the fuel would become uncovered.

    In my Opinion they exaggerated the level of danger. Why i say that:
    1. They gave no statistic as to likelihood of another significant earthquake.
    2. They gave no information as to the strength of the pool as it stands. TEPCO added supports below it last year.
    3. They gave a purely emotional appeal that late next year is too long to wait. What is their basis for that assessment? There are good reasons to never rush any work around big machinery.
    4. Daichi indeed has another pool onsite for spent fuel storage and it's at ground level. That's where they take the spent fuel using casks as shown in the video. As the professor says they have to clean up the pool and prepare another crane first.

    SO - my opinion is the video you linked is intended to worry people . It appears to have done that.

    You Japanese have done a far better job with your spent fuel than we have here. I was astonished at how little is actually in your pools compared to ours.

    Now - i worked a lifetime in a nuclear plant so i may not be impartial, though i do try to be.
    For what this is worth - my son's employer has a position opening up at a US Navy base south of Tokyo. I am encouraging my son to apply.
    I am not worried about that spent fuel pool. I would gladly go over there and work at Daichi if the opportunity arose.
    That's how (un)worried I am.

    Doubtless this post will draw criticism.

    So just let me end by saying -
    If the drying of the fuel is as the Professor said "The End",, well, that's easy - keep it wet.

    And - Praise be to the workers who are cleaning up that mess. They probably don't get very many encouraging words.

    old jim
  4. Apr 19, 2012 #3


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    I don't believe that Koide is necessarily correct.

    The page shows recent historical seismicity in the vicinity of Fukushima since 1973. Large earthquakes, like the great Tohoku event on 11 March, 2011 are few and far between, and so far have happened offshore.

    I will try to find a better representation of seismic activity in the vicinity of Fukushima Daiichi (37.421469 N, 141.032567 E).

    One has to look at the data to better understand the type of earthquake that might be expected (based on historical events) near Fukushima. The plant was designed for a certain level of earthquake, and in fact did survive the initial earthquake, although there apparently was some damage at the plant.

    The subsequent tsunami disable and destroyed the emergency cooling systems and power at the plant, and that precipitated the accident.

    Koide is not too careful with his comments. The core of unit 4 and the pressure vessel was empty. The core obviously did not explode. It is surmised that hydrogen came from unit 3 through common duct work, and the resulting ignition/fire damaged the upper containment of unit 4.

    Here is a report by World Nuclear News concerning TEPCO's work to secure Fukushima Daiichi Unit 4 and it's spent fuel pool.
  5. Apr 20, 2012 #4
    That adressed the seismic and building structural side of things. But whether or not it's very, very, very unlikely for the pool to actually collapse, the probability for this to happen is certainly not zero. And nobody can argue that it's undoubtly higher for this specific fuel pool than for all the other undamaged ones.
    So in my opinion you should also explain if Koide's near apocalyptic scenarios are probable or not in case the pool actually collapses.

    Granted, I agree that I don't believe in a collapse of the SFP either. But this kind of thinking, to stop at the "the probability is so low that it will never, ever happen during our lifetime" point, is exactly what brought us in this kind of mess in the first place. Nobody thought about consequences of a station wide SBO. The possibility was obviously there, but nobody wasted even a thought about it just because this even seemed so unlikely that thinking about it properly would be a waste of time.

    You made your point that his fears of a collapse are unreasonable but that a very minor possibility for this to happen is there. So extend your explanation to this very unlikely case. Everything else would be dispersing salt in his eyes.

    No offense, but I think your answers are symptomatic for at least the public stance of the nuclear industry as a whole. "The accident can't happen. Period. Therefore there is no need to evaluate possible consequences. If someone does he's unreasonable since, as already stated, the accident can't happen."
    Last edited: Apr 20, 2012
  6. Apr 20, 2012 #5
    There is an increased risk of an M7 class quake around the plant suggested by this recent paper:

    "Tomography of the 2011 Iwaki earthquake (M 7.0) and Fukushima nuclear power plant area"

    "Our results suggest that the Iwaki earthquake was triggered by the ascending fluids from the Pacific slab dehydration and the stress variation induced by the Tohoku-oki mainshock. The similar structures under the Iwaki source area and the Fukushima nuclear power plant suggest that the security of the nuclear power plant site should be strengthened to withstand potential large earthquakes in the future."
  7. Apr 20, 2012 #6


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    I have not stated anything that resembles the comment I bolded, nor have I or anyone here indicated that a future strong seismic event is improbable so that it's not worthy of any further consideration, nor have I or anyone here dismissed the consequences of a further seismic event or the rupture of the spent fuel pool. I have not even commented on the consequences, since that requires an evaluation of available evidence and data.

    Unit 4 shutdown 30 Nov, 2010 which is 507 days ago during which time, various radionuclides have decayed, and more importantly, the Xe, Kr and I radioisotopes have decayed. However, one must consider the initial inventory, isotopic vector and decay chains to make a reasonable estimate of further release from the site.

    Meanwhile TEPCO is working to secure the facility. I do not have access to details, e.g., is the seismic capability of the building adequate for an earthquake of a given magnitude - or the maximum ground acceleration physically possible at the site.

    I think panic is unwarranted and certainly is unproductive.
  8. Apr 20, 2012 #7

    jim hardy

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    @Clancy - had the TV reporters addressed those questions
    and used "experts" with geology and construction expertise,
    the report would have been much more persuasive.

    The way it was presented actually impressed me as "fearmongering"
    because the kindly professor(presumably of nuclear engineering?) was used as a stage prop
    to give to their unsupported claims of imminent danger from earthquake and pool structural weakness , the false impression of expert validation.

    I'm not claiming i know anything about geology or civil engineering.
    But neither did anybody on that TV clip. It was a long advertisement for an influence group.

    So - @ OP - get more information.

    I tried to remain neutral -
    but i am perhaps oversensitive to biased reporting. We are inundated with it here in USA.
    I blame our advertising industry for a general decline of integrity in all areas of society. We are bombarded with exaggerated or outright false claims from the time we are toddlers just big enough to notice a TV screen . Overstepping bounds of honesty to gain advantage is imprinted early as natural and acceptable behavior.
    Sure wish i could live long enough to see what history says about the era 1950-2050.

    old jim
  9. Apr 20, 2012 #8


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    Koide Hiroaki is assistant professor at Kyoto University Research Reactor
    Institute (KU-RRI).

    He is apparently opposed to nuclear energy.
  10. May 6, 2012 #9
    There are a lot of panic laden posts around the internet at the moment referring to a "mass extinction event" if the unit 4 spent fuel pool collapses.

    I was going to include a few links but the forum wont let me (less than 10 posts). Just search this quote for example: “If they are MOX fuel, containing six percent plutonium, one fuel rod has the potential to kill 2.89 billion people.”, a statement widely quoted, originating from Christina Consolo (who I note is a photographer, not a nuclear scientist.)

    Most of the reports refer to how cataclysmic it would be if there are MOX fuel assemblies in that storage pool, but none of them say whether there actually are. Do we know whether there is any MOX fuel in the unit 4 pool? Is a mass extinction event really a possible outcome here?

  11. May 6, 2012 #10


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    There were 32 MOX fuel assemblies in Unit 3 core. As far as we know there were no MOX fuel assembies in Unit 4. The core had been removed after the last cycle and had been placed in the spent fuel pool, which is normal.

    However, all used/spent fuel does contain Pu isotopes (Pu-239, 240, 241, 242) and other transuranics, but they are typically about 1% of the fuel structure.

    There is no possibility of 'mass extinction'. Unfortunately, there is a lot of nonsense on internet.
  12. May 6, 2012 #11


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    Tepco assessed the seismic safety of unit 4's reactor building in the report dated 28 May 2011 : http://www.tepco.co.jp/en/press/corp-com/release/11052801-e.html

    The NISA's reply to this report is available at http://www.nisa.meti.go.jp/english/press/2011/06/en20110607-2.pdf [Broken]

    If Koide knew about some specific flaw in that report, he would say it. As far as I know he is not saying anything specifically against that report. Also, as far as I know, Koide is not a mechanical engineer.

    If there was a big worry about unit 4's building, I think nuclear-critical groups like the CNIC would be vocal about it. In the latest CNIC report on Fukushima, dated March/April 2012, there is no specific worry about unit 4's seismic safety : http://cnic.jp/english/newsletter/nit147/nit147articles/fuku_statusandcorium.html
    Last edited by a moderator: May 6, 2017
  13. May 6, 2012 #12

    jim hardy

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    glad you noted her vocation is not scientific.

    It gives some people a sense of power to shout scary things. Just watch children playing. We're supposed to outgrow it.

    I wouldn't use plutonuim for pizza topping,
    but remember there were Manhattan machinists who worked plutonium metal in lathes .

    http://www.neimagazine.com/story.asp?storyCode=2029280 [Broken]
    Last edited by a moderator: May 6, 2017
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