Gone Fission: If Fukushima Nukes Are Seeing Fission Bursts, It Turns “Our Entire Understanding of Nuclear Safety On Its Head”

Fears of Fission Rise at Stricken Japanese Plant

TOKYO — Nuclear workers at the crippled Fukushima power plant raced to inject boric acid into the plant’s No. 2 reactor early Wednesday after telltale radioactive elements were detected there, and the plant’s owner admitted for the first time that fuel deep inside three stricken reactors was probably continuing to experience bursts of fission.

Sure, it only merits page A17 in today’s New York Times, but the story is still a bombshell for the troubled nukes:

On Wednesday, the plant’s operator, the Tokyo Electric Power Company, said that gas from Reactor No. 2 indicated the presence of radioactive xenon and other substances that could be byproducts of nuclear fission. The presence of xenon 135 in particular, which has a half-life of just nine hours, seemed to indicate that fission took place very recently.

Trade Minister Yukuo Edano censured Japan’s nuclear regulator, the Nuclear and Industrial Safety Agency, for failing to report the discovery to the prime minister’s office for hours, according to local media reports.

The developments added to disquiet over how information related to the disaster has been handled. For almost two months after the March 11 earthquake and tsunami knocked out vital cooling systems, setting the stage for disaster, both company and government officials declared it was unlikely that any meltdowns had occurred. They finally conceded that melted fuel had likely breached containments in three reactors, and that it was likely pooled at the bottom of the vessels.

A 12-mile exclusion zone is still in effect around the plant. More than 80,000 households were displaced.

I should say upfront that cost, not safety, is the real problem with nuclear power as a climate solution today (see “Does Nuclear Have a Negative Learning Curve?” and “An introduction to nuclear power.”

But safety is a genuine concern.  Here’s the “good news” on Fukushima’s fears of fission:


On Wednesday, Tokyo Electric said that the amount of xenon detected was small, and there was no rise in temperature, pressure or radiation levels at the reactor. Researchers were double-checking the data to make sure there were no errors, the company said. Experts concurred that it was possible that Tokyo Electric had made a simple error in its measurements.

But the urgent injection of boric acid underscored that the company was operating on the assumption that the measurements were valid. A naturally occurring element, boron, soaks up the neutrons released when an atom is split so that those neutrons cannot go on to split other atoms when material “goes critical” in the process of fission. Nuclear power plants harness the energy released in the form of heat to produce electricity.

It is impossible to determine exactly what state the fuel is in, given that even an intact reactor can offer only gauges for temperature, pressure and neutron flow, not visual observation. That lack of clarity is one of the most resonant lessons of the Fukushima disaster, when those trying to guide the response and assess the danger had to operate by what amounted to educated guesswork.

So what is happening?

In reactors of the design used at Fukushima, that chain reaction is normally stopped when the operator gives a command to insert control rods, which rise up from the bottom of the core and separate the fuel assemblies. But when the cores of three reactors at Fukushima melted, a large part of the fuel presumably formed a jumbled mass in the bottom of the vessel, and without a strict gridlike geometry, the control rods cannot be inserted. Some of the fuel has escaped the vessel, experts believe, and is in spaces underneath, where there is no way to use control rods to interrupt the flow of neutrons.

The jumble of material and conditions had seemed very unlikely to be able to produce sustained fission, but intermittent criticalities have long been suspected.

Junichi Matsumoto, a Tokyo Electric spokesman, acknowledged episodes of fission, telling a news conference: “There is a possibility that certain conditions came together temporarily that were conducive to re-criticality,” and that the measurements indicated a burst that occurred at a slightly higher rate than prior cases. “It’s not that we’ve had zero fission until now,” Mr. Matsumoto said. “But at this point, we do not think there is a large-scale and self-sustained re-criticality.”

No, that would be hard to imagine.  But if the fission is real, then it is something to worry about:

The three reactors — together with spent fuel rods stored at a fourth damaged reactor — have been leaking radioactive material since the initial disaster, and new episodes of fission would only increase their dangers.

“Re-criticality would produce more harmful radioactive material, and because the reactors are damaged, there would be a danger of a leak,” said Hiroaki Koide, assistant professor at Kyoto University’s Research Reactor Institute, whose prescient warnings about nuclear safety have won him respect in Japan.

Mr. Koide holds that the nuclear fuel at the three reactors probably melted through containments and into the ground, raising the possibility of contaminated groundwater. If much of the fuel was indeed in the ground early in the crisis, the “feed and bleed” strategy initially taken by Tokyo Electric — where workers pumped cooling water into the reactors, producing hundreds of tons of radioactive runoff — would have prevented fuel still in the reactor from boiling itself dry and melting, but would not have done anything to reduce danger from fuel already in the soil — if it got that far. Workers have now put in place a circulating cooling system that recycles water, which results in less runoff.

Tokyo Electric does not deny the possibility that the fuel may have burrowed into the ground, but its officials say that “most” of the fuel likely remains within the reactor, albeit slumped at the bottom in a molten mass.

But even in their most dire assessments, some experts had not expected even bursts of re-criticality to occur, because it was unlikely that the fuel would melt in just the right way — and that another ingredient, water, would be present in just the right amounts — to allow for any nuclear reaction. If episodes of fission at Fukushima were confirmed, Mr. Koide said, “our entire understanding of nuclear safety would be turned on its head.”

Other experts are concerned, too:

A former nuclear engineer with three decades of experience at a major engineering firm, meanwhile, said that sustained re-criticality remained highly unlikely. But his main concern was that officials could not pinpoint the exact location of the nuclear fuel — which would greatly complicate the cleanup.

The engineer, who has worked at all three nuclear power complexes operated by Tokyo Electric, spoke on condition of anonymity because he did not want to be identified by his former employers. He said that tiny fuel pellets could have been carried to different parts of the plant, like the spaces under the reactor during attempts to vent them in the early days. That would explain several cases of lethally high radiation readings found outside the reactor cores.

“If the fuel is still inside the reactor core, that’s one thing,” he said. But if the fuel has been dispersed more widely, then we are far from any stable shutdown.”

Stay tuned.

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29 Responses to Gone Fission: If Fukushima Nukes Are Seeing Fission Bursts, It Turns “Our Entire Understanding of Nuclear Safety On Its Head”

  1. Mr. Romm, you infer by your comments that you are knowledgeable about nuclear energy but then you make sweeping statements such as “I should say upfront that cost, not safety, is the real problem with nuclear power as a climate solution today…” when that is just about Light Water Reactors and neither condition pertains to the best Small & Modular Reactor designs. To write off nuclear energy based on the Light Water Reactor designs is a sin of omission.

  2. John Tucker says:

    I would imagine if the fuel melted together it would be entirely possible. If its contained I just dont see the big deal.

    Nuclear fuel emits energy and isnt that hard to find.

    ¨Re-criticality¨ sounds like something someone would run around frantically screaming without knowing what it actually is.

  3. Cheryl Rofer says:

    It appears that the radioactive xenon is coming from spontaneous fission of curium isotopes normally produced in a reactor.

  4. Joe Romm says:

    If I had a dollar for everyone who had a PowerPoint presentation for some noncommercial technology that ended with cost-effectively low-carbon power, I could retire. Call me back in 10 years when we have some real world #s and testing for your silver bullet.

  5. Lou Grinzo says:

    I get a lot of queries about “what I think of nuclear power”, “is it THE answer”, etc., and I always say the same thing:

    We desperately need an ultra-low carbon source of electricity, preferably virtually zero carbon. No rational person disputes that. And I will wholeheartedly support nuclear power the second I’m convinced we have any bloody idea how to manage it over its entire lifecycle in a way that’s safe and at an acceptable price. (Notice that I’m not demanding a solution that’s cheaper than coal when we have no price on carbon emissions, merely one with a price we can tolerate.)

    Fukushima, the immense cost of plant decommissioning, which the UK is wrestling with now and the US will have to deal with in time, waste storage and management, cooling water issues, etc. all tell me that we’re not even close to having the right combination of technology, infrastructure, and social structure in place to use nuclear power with the appropriate level of safety and efficiency.

    By all means, keep researching Small Modular Reactors and other possible solutions to our own ineptitude. But I’m as skeptical of those advances as Joe is in his response to another comment above.

  6. John Tucker says:

    Isnt that same argument applicable to the entire intermittent solar power generation scene?

    If I had a dollar…

    Anyway, Its clear you are working off some other technical layer / disaster mitigation / scenario bias or world view perhaps that I dont understand and/or you have not put forth here at least not recently.

    It would be nice to actually discus that and not waste time, like everywhere else in unproductive argument.

  7. Theodore says:

    I would like to know what prevents the use of a robot with big jaws that could just tear its way in there, grabbing and tearing off or cutting whatever was in the way until the fuel in small chunks was removed to steel boxes in a controlled remote location. I know that some robots are destroyed by the intense radiation, but it seems to me that the sensitive parts could be encased in lead, leaving only non-sensitive components exposed. It might also be possible to put the sensitive components at a distance and have only connecting hydraulic or mechanical connections to the working end.

  8. Mark Shapiro says:

    Nuclear power is completely anathema to free market capitalism and to freedom itself.

    Nuclear power is highly centralized. It requires big government subsidies, regulation, and bureaucracy. It needs strong central governments and then makes those governments bigger. Government bureaucracies grow to create nukes, and the defense bureaucracies grow even more to make them “secure”.

    Nuclear power can never be free-market because no owner or operator can handle the risk or liability.

    Nuclear power is the enemy of every value that conservatives hold dear, yet most conservatives today support it. Why? Because nuclear power is seductive, and people like wielding power.

  9. John Tucker says:

    Like an iGodzilla?

    I think they like things to cool down then carefully go in and remove everything. Time is your friend. The energy present in some of the debris is sufficient to burn/vaporize materials. ( )

  10. prokaryotes says:

    3-eyed Fish Found Near Argentinean Nuclear Power Plant

    You’ve heard of life imitating art, but now a fish found in Argentina resembles something you’d see on “The Simpsons” — and it’s not making environmentalists laugh.

    Back in 1990, the long-running series did an episode that featured “Blinky,” a three-eyed fish that cropped up near the Springfield nuclear power plant, where Homer worked.

    Now, 21 years later, fishermen in Córdoba, Argentina caught a three-eyed wolf fish in a reservoir near a local nuclear power plant, according to

  11. Raul M. says:

    With us not really able to deal with the natural disasters the us had last year it is a dream that the us could deal with a nuke disaster in Nebraska that could result from next years flooding (dam breaking) all the way down the river.
    But even so feedbacks from carbon cycle will start us running for shelters.

  12. Chris Winter says:

    If episodes of fission at Fukushima were confirmed, Mr. Koide said, “our entire understanding of nuclear safety would be turned on its head.”

    I have to wonder who Mr. Koide refers to when he says “our understanding.” John G. Fuller, in We Almost Lost Detroit, argues convincingly (by quoting independent experts) that “spontaneous assembly” in reactor meltdowns could not be ruled out. This was the big concern in his story about the Fermi breeder reactor’s partial meltdown in 1966.

    Fuller himself was not a reactor expert, and he took “spontaneous assembly” to mean a fission explosion. This fear is probably overblown. But plenty of prompt-criticality accidents have happened in the processing of nuclear materials, and so I doubt that every nuclear safety expert would be as surprised as Mr. Kiode seems to be.

  13. Raul M. says:

    This Year.

  14. John Tucker says:

    There isnt time left anymore for a half hearted renewables push. Nuclear power needs to be an option even if the conversion to clean energy was going much better than it is.

    Im sorry, it is ridiculous to be across the board ¨anti nuclear power¨ now.

    World emissions of carbon dioxide soar higher than experts’ worst case scenario for climate ( )

  15. John Tucker says:

    Thats not really how it works. Point mutations that would cause that kind of deformity would also kill the fish or have other symptoms in most cases, as would disruptions in cell divisions in embryonic development.

    If it is a contaminant its most likely a chemical one which tend to be much more efficient at that kind of thing.

    It actually more fits descriptions of deformities near oil sands on the Athabasca River. PAH related.

    It would be beyond ironic if some ¨environmentalists¨ facilitated pollution by incorrectly fingering nuclear power because of a Simpsons joke.

  16. John Tucker says:

    Are you thinking here that turning conservatives off to nuclear is going to make them embrace solar power or any clean energy in reasonable acceptance of their error?

    Do you think solar and nuclear funds come from the same allotments and earmarks?

    I dont see the reasoning here.

  17. Theodore says:

    John – you should read a lot of Helen Caldicott books and watch her videos. They would turn you inside out and make you sick. I just finished reading “Nuclear Power is Not the Answer”.

    I don’t trust her facts, but I do love her attitude. It matches mine exactly. If I made energy policy for the world, I would shut down every uranium mine today and let the blackouts roll. I would also ban all new fossil fuel power plant construction immediately. People would have to build renewable energy in a really big hurry or be in the dark when the uranium ran out.

  18. Michael Glass says:

    Two points about this article.

    a) Criticality is far from the only problem.

    The basic problem is heat. To this day 15,000 square km remain evacuated in the East Ural Radioactive Trace, several times larger than the Chernobyl zone and more than an order of magnitude larger than the Fukushima zone. It was a spent nuclear fuel facility that lost its cooling. No criticality occurred and no nuclear reactors were present.

    b) I think the Fukushima reactors will be continuously cooled for years before anybody can open the reactor vessels and look inside.

    It was six years after, in 1985, that TMI-2 was opened up. Defueling took five more years. The final report (which is an interesting skim—there were a whole lot of interesting engineering problems) says that about 1,100kg of fuel remains.

    Potential criticality outside the reactor vessel was a concern at TMI also. Hundreds of kg of fuel fragments were swept out of the vessel by the water flow, mostly lodging elsewhere in the cooling system.

    At some point—maybe already—there will be remote controlled cameras. But most knowledge of what is inside will come from reading entrails for quite a long time.

    An editorial comment: I think a lot of the problems with utilizing nuclear energy come from dogmatism. The nuclear industry refuses to face some of its problems squarely because to do so would be to admit the magnitude of the problems, the anti-nuclear movement refuses to face the benefits squarely for the complementary reason.

  19. David B. Benson says:

    As is clearly explained in a World Nuclear News article, the discovery of xenon radioisotopes without the other signature radioactives of nuclear fission in a reactor is indicative of the spontaneous decay of U-235. In other words, a nothing story.

    The possibility of nodules of uranium oxide spilled all over the floor (or into the ground below) of the reactor compartment cannot be ruled out, but actually represents less of a concern than corium. The radiological evidence is that the corium has essentially ceased fissioning with all three reactor’s temperature readings well below the boiling point of water.

    Let’s not invent trouble, please. [I’ll also point out that the article in today’s TNYT contains a grevious error regarding the control rods; one which a competent fact checker would have spotted; I suppose that’s beyond TNYT these days.]

  20. Bill Goedecke says:

    If you all want news about Fukushima check out this site:

  21. Uncle B says:

    China has a campaign for safer, cheaper nuclear energy. tells some of this story. Fact is : it is possible, proven by American scientists in the 1960’s! Thorium is much safer to mine transport and process, is very much more plentiful, and is totally consumed in LFTR reactors leaving behind very little waste, of benign nature, safe to humanity after only three hundred years storage, and plutonium free, The Pan Eurasian Empire rising in the East today will be Thorium powered in a decade! They will become oil free, and manufacture without the monkey of foreign oil parasite nations on their every move. They will bring products to market in so much cheaper than American products as to destroy American manufacturing.

  22. Theodore says:

    The reason the anti-nuclear movement refuses to face the benefits of nuclear power is that there aren’t any. Renewables are both safer and cheaper.

  23. Jim says:

    Arnie Gundersen has been talking about criticality at Fukushima for some time; see

  24. Mark Shapiro says:

    I would settle for people simply evaluating energy technologies based on their actual characteristics.

    The fact that conservatives don’t acknowledge nuclear’s anti-market and anti-freedom nature fascinates me.

  25. Pangolin` says:

    “Renewables are both safer and cheaper.”……and faster to deploy.

    In the same 10-12 year time it takes to get a nuclear power plant built the equivalent power production in wind and solar can be…. sited, manufactured and installed in 6 months (distributed solar) to 3 years (major wind turbine field), producing power, provided a full return on energy inputs and has paid for, or almost paid for it’s investment cost, including financing.

    All that before a nuclear power plant can light a 1 watt LED.

    Energy savings investments such as improved lighting or ground-loop heating and cooling for buildings are much, much faster at achieving payback. By comparison, the Fukishima reactores will never repay their energy investment or ultimate cost.

  26. Pangolin` says:

    Dog help us the believers in the Magic Throrium Bunny are here. They the Ron Paul fanatics of the energy world. But there is always this mysterious catch…… Why is it that there are no commercial grade thorium reactors anywhere in the world?

    The answer is that engineers can’t figure out how to build one that won’t kill it’s operators and be affordable to run.

    It’s not lack of investment funds; China built the Three Gorges Dam at enormous cost. It’s not lack of engineers. It’s certainly not lack of thorium. Somewhere in the chain of operations where one handles thorium fuel it gets really, really, dangerous and the engineers that build and handle nuclear plants don’t like it.

  27. David B. Benson says:

    AFAIK the Indians continue to work on one.

  28. David B. Benson says:

    Given how cold the reactors are, re-criticality is (1) unlikely to any degree and (2) unproblematic in any case.

  29. TEPCO has released calculations which agree with the conclusion that spontaneous fission (not caused by external neutron source) is the source of the short-lived Xenon in the samples. Two fissile isotopes of Curium are highlighted as the source, rather than Uranium. See Nov 4 technical report. I was surprised that the Xe was detected on charcoal filter. I’ve worked at many nuclear plants, and we collected air in a flask for noble gas sampling rather than draw it through a filter. The TEPCO paper does apply a multiplication factor of 1,566 to account for very low efficiency of charcoal in capturing Xe