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Japan Power Hardware

Spontaneous Fission In Fukushima Daiichi Unit 2 266

Posted by Soulskill
from the gone-fission dept.
Kyusaku Natsume writes "Tokyo Electric Power Co. said Wednesday that some of the melted fuel in reactor 2 at the Fukushima No. 1 nuclear plant may have triggered a brief criticality event. Tsuyoshi Misawa, a reactor physics and engineering professor at Kyoto University's Research Reactor Institute, said that if Tepco's data are correct, 'it's clear that the detection (of xenon-133 and -135) comes from nuclear fission.' Tepco spokesman Junichi Matsumoto said the test results suggest that either small-scale fission occurred in the melted fuel, or conditions to trigger criticality were temporarily met for some other reason. He said the same thing could also happen at reactors 1 and 3. But because the reactor's temperature and pressure level have not changed, the fission would not have been large-scale, Matsumoto said, adding that it would not thwart Tepco's schedule for achieving a cold shutdown at the reactors. In response, boric acid water was injected again on November 2. On the plus side, the concentration of radioactive materials in the air is low enough that workers inside some areas of Fukushima Daiichi workers soon will not have to use full face masks."
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Spontaneous Fission In Fukushima Daiichi Unit 2

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  • I'm half expecting Godzilla to emerge from off shore and stomp the rest of the plant to bits.

    Truth may be the first casualty of war, but it seems to be bound up and stuffed into a file cabinet in a disused lavatory in the basement of a building with a sign "Beware the leopard" on the door, when there's a disaster and a business involved.

    • by SomeoneGotMyNick (200685) on Thursday November 03, 2011 @01:10PM (#37937074) Journal

      Heaven forbid a moth would land on that fissle material...

      • Re: (Score:3, Insightful)

        by ackthpt (218170)

        Heaven forbid a moth would land on that fissle material...

        Rather a good thing that (so far) radiation tends to kill things, rather than mutate them like good ol' fiction suggested for 70, or more years.

        but all it takes is once ...

        • by afidel (530433) on Thursday November 03, 2011 @03:03PM (#37938860)
          Actually, the field mice around Chernobyl have a much higher rate of mutation including a 300% increase in fertility rates compared to those outside the exclusion zone which more than makes up for the slightly increased morbidity rate. It was one of the more interesting tidbits in a recent PBS show on research in the exclusion zone.
    • by EdZ (755139)
      I keep hearing of complaints about TEPCO misinformation etc. Reading the IAEA and NISA reports has seemed fine to me, where is all this disinformation coming from? None of it seems to be filtering though to anywhere reputable.
      Of course, newspapers reporting headlines like "Japan secretly enlarges evacuation zone" after the government invites international media to a press conference on expanding the evacuation zone probably doesn't help.
    • Re: (Score:3, Insightful)

      by Jawnn (445279)

      I'm half expecting Godzilla to emerge from off shore and stomp the rest of the plant to bits.

      Truth may be the first casualty of war, but it seems to be bound up and stuffed into a file cabinet in a disused lavatory in the basement of a building with a sign "Beware the leopard" on the door, when there's a disaster and a business involved.

      It's so quaint when people are surprised that the nuclear industry lies to the public about the risks involved, or that the government is almost always complicit in the perpetration of those lies. The truth about nuclear energy, they way it is typically delivered (as cheaply as possible), is that it is staggeringly dangerous. Incidents are, happily, fairly rare, but they are catastrophic when they do occur. That truth is bad for business if it is dealt with honestly, by anyone, in the public square. So yeah

      • by afidel (530433)
        No, deaths per MWHr for nuclear are by far the lowest of any power source available, including things like wind, solar, and hydro. This is true even if you take the worst case cancer numbers which are probably off by at least an order of magnitude.
        • by JWSmythe (446288)

          Hold on...

          You're saying that two fledgling industries (wind and solar) have had a higher death rate per MWHr than an industry who has been around for years, and have many employees who have never even been near the outer shell of the reactor?

          Ya, I found your reference, since you kinda forgot to post it.
          http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html [nextbigfuture.com].

          Energy Source Death Rate (deaths per TWh)
          Coal - world average 161 (26% o

          • by Imrik (148191)

            While you make some good points about the statistics used, a couple points. First, deaths per TWh is more appropriate than deaths per man hour since you're comparing the safety of the power source, not the safety of the job. Second, including nuclear weapons might be good for showing what public perception of danger is, but it would be unreasonable to consider them as relevant to power safety. Besides, if you include deaths by nuclear weapons you would also have to include deaths by gunpowder in the coal

  • Subject (Score:3, Funny)

    by Anonymous Coward on Thursday November 03, 2011 @01:09PM (#37937058)

    Obviously it's fake, we all know that after shutdown there CAN'T be uncontrolled fission going on. It's physically impossible, you dumb hippies!

    • Re:Subject (Score:4, Insightful)

      by ackthpt (218170) on Thursday November 03, 2011 @01:17PM (#37937178) Homepage Journal

      Obviously it's fake, we all know that after shutdown there CAN'T be uncontrolled fission going on. It's physically impossible, you dumb hippies!

      I dunno .. with what happens when all hell breaks loose in a reactor losing cooling, superheating and such - granted the period would likely be very, very short, but you could get just about anything from it (much of which will have very short half-lives) but the unpredictable nature of the event and outcomes shouldn't be underestimated.

      Also .. rather like this bit: inside some areas of Fukushima Daiichi workers soon will not have to use full face masks." Right. Do I have any volunteers?

      • Re:Subject (Score:5, Interesting)

        by pixelpusher220 (529617) on Thursday November 03, 2011 @01:23PM (#37937272)

        Right. Do I have any volunteers?

        Actually the elderly in Japan volunteered to be the workers early on in the crisis since they were already old and wouldn't be much more adversely affected by radiation cancers in 20 years...

        • by ackthpt (218170)

          Right. Do I have any volunteers?

          Actually the elderly in Japan volunteered to be the workers early on in the crisis since they were already old and wouldn't be much more adversely affected by radiation cancers in 20 years...

          There were also some very heroic company workers. Though I wonder how many of them performed their tasks out of a sense of duty versus told they had nothing to worry about, the levels were safe and their suits would protect them.

          • Re: (Score:3, Insightful)

            by sjames (1099)

            There were also some very heroic company workers. Though I wonder how many of them performed their tasks out of a sense of duty versus told they had nothing to worry about, the levels were safe and their suits would protect them.

            You write as if those conditions have been proven untrue.

            • by ackthpt (218170)

              There were also some very heroic company workers. Though I wonder how many of them performed their tasks out of a sense of duty versus told they had nothing to worry about, the levels were safe and their suits would protect them.

              You write as if those conditions have been proven untrue.

              I believe we have seen that the stated conditions turned out to be far worse than were reported at the time, with this article simply adding to that body of evidence. Company officials were telling the government of Japan and media that things were not too bad, continuously. When the reactor building popped its cork they finally had to admit they didn't really know how bad things were.

              • by sjames (1099)

                And yet, not a single report of a radiation injury. Nobody's suit failed to protect them, nobody exposed to worryingly high radiation. Nobody.

                They did find a bit of a hot spot in Tokyo, but that turned out to be some luminescent paint left under some floor boards 50 years ago.

                Frankly, the doomsayers' faces should be beet red now with heat shimmers rising from them, but they're far too shameless for that.

                Again, where's the dead? The injured? The glow in the dark? Where's Godzilla (or at least a disgruntled g

                • And yet, not a single report of a radiation injury

                  Did you bother looking for any? Because I didn't have any trouble finding dozens of such reports after ten seconds of research.

                  Which really didn't surprise me, since I remember reading them in most of the major newspapers and online news feeds.

                  Over 20 workers had been injured by 18 March, including one who was exposed to a large amount of ionizing radiation when the worker tried to vent vapour from a valve of the containment building. Three more workers we

    • Re:Subject (Score:5, Informative)

      by DaveAtWorkAnnoyingly (655625) on Thursday November 03, 2011 @01:54PM (#37937784)
      I'm trying to work out if you're being sarcastic or not. Of course you can have uncontrolled criticalities in a shutdown reactor. All you need to do it put enough fissionable material together and you'll get a criticallity event. They're usually just flashes and last fractions of a second, but it does happen. History is littered with these events. A shutdown reactor with the right levels of boron, still with core geometry intact will not have un-controlled criticalities, in that you are correct. However, this reactor does not have core geometry anymore and you can therefore not prove that the boron is getting everywhere and that the fuel hasn't managed to arrange itself into fissionable quantities.
  • by gstrickler (920733) on Thursday November 03, 2011 @01:14PM (#37937132)

    From Mainichi Daily News [mainichi.jp]

    Tokyo Electric Power Co. said Thursday the detection of radioactive xenon at its stricken Fukushima Daiichi power plant, indicating recent nuclear fission, was not the result of a sustained nuclear chain reaction known as a criticality, as feared, but a case of "spontaneous" fission.

    • by cryfreedomlove (929828) on Thursday November 03, 2011 @01:19PM (#37937216)

      From Mainichi Daily News [mainichi.jp]

      Tokyo Electric Power Co. said Thursday the detection of radioactive xenon at its stricken Fukushima Daiichi power plant, indicating recent nuclear fission, was not the result of a sustained nuclear chain reaction known as a criticality, as feared, but a case of "spontaneous" fission.

      Do you believe any explanation from Tokyo Electric at this point? They have told enough lies about Fukushima that I now assume they are lying every time they open their mouths. Has this been verified by an independent 3rd party?

      • Do you believe any explanation from Tokyo Electric at this point? They have told enough lies about Fukushima that I now assume they are lying every time they open their mouths. Has this been verified by an independent 3rd party?

        I would tend to agree about TEPCO. Anything they say needs to be taken with a healthy dose of Potassium Iodide. Given that, I'm not sure it's been 'verified' - one explanation is that the readings are spurious, but for another, less panicky take on the issue, read this [nature.com].

      • by Darth_brooks (180756) <clipper377 @ g m ail.com> on Thursday November 03, 2011 @04:16PM (#37939936) Homepage

        Disagree.

        After reading reading Tuesday's account of the first 24 hours at Fukishima, it's pretty clear that the scope of the accident exceeded what the engineers thought was possible. From there there chain of "we believe" and "probably" and "fairly certain's" began flowing until several days later when the full extent of the accident became clear.

        With any major incident, hindsight allows us to say "Look! You were bullshitting us when you said XYZ!" Did the head of TEPCO say everything was hunky dory an hour after the tsunami? Maybe. But was that because the various people charged with reporting the situation to him told him that things were okay, or because he was a genuine piece of shit who knew that they were 24 hours from the worst nuclear disaster in his countries history, and wanted to cover his own ass? Proving what everyone up and down the chain of command knew at what point in time is almost impossible, because we know the people on the ground couldn't get a good handle on what was going on for a couple days.

        On top of that, you honestly expect that information to filter up and back down through the proper channels and out to the media (all of whom immediately started checking how to correctly spell "Chernobyl" the instant someone said "nuclear power plant") AND expect that information to be disseminated out responsibly? YEAH. RIGHT.

        Fukushima is not some watershed moment that finally drives the stake in the evil demon of nuclear power. At least it shouldn't be. This accident (a top 25 all time earthquake followed by possibly the worst Tsunami in the nation's history, proved that a positively ancient nuclear plant wasn't as prepared as it could have been. Even in those circumstances there still wasn't ANY loss of life.) should be a signpost that says we need to modernize nuclear power, not bury it.

        OJ Simpson killed more people than the Fukushima disaster.

  • No (fission) Nukes (Score:5, Interesting)

    by cryfreedomlove (929828) on Thursday November 03, 2011 @01:14PM (#37937140)
    I was a proponent of expanding nuclear fission electricity generation until Fukushima. Fission is a zero-carbon system and cheap at massive scale. However, my enthusiasm also assumed that the industry was regulated and transparent enough to be safe. Clearly it is not. The bigger nail in the coffin for me, however, is that the first month or more of issues with Fukushima were clouded with lies from the utility that runs the plant and from the Japanese government itself. Why should we ever trust anything the utilities say about nuclear safety ever again? They don't have the moral integrity to handle the responsibility of running a safe nuclear fission industry.

    I still hold out hope for the safe cold fusion dreams. It may not be a rational hope but it would be awesome.
    • by ackthpt (218170) on Thursday November 03, 2011 @01:23PM (#37937268) Homepage Journal

      I was a proponent of expanding nuclear fission electricity generation until Fukushima. Fission is a zero-carbon system and cheap at massive scale. However, my enthusiasm also assumed that the industry was regulated and transparent enough to be safe. Clearly it is not. The bigger nail in the coffin for me, however, is that the first month or more of issues with Fukushima were clouded with lies from the utility that runs the plant and from the Japanese government itself. Why should we ever trust anything the utilities say about nuclear safety ever again? They don't have the moral integrity to handle the responsibility of running a safe nuclear fission industry.

      I still hold out hope for the safe cold fusion dreams. It may not be a rational hope but it would be awesome.

      In my childhood I lived in an area where a proposed nuclear plant was to be built. The power company behind it started with a barrage of PR about clean, safe energy. Eventually, after years of changing regulations and legal battles they scrapped the nuclear plans and turned it into a natural gas plant.

      That preceeed Chernobyl, Three Mile Island and, of course, Fukushima.

      Want to conserve energy? Increase rates.

      • by Bardwick (696376)
        Nuclear is probably the most regulated industry in the world. You do realize the issue was not caused by lack of regulations. I seem to recall that is was a really big freaking earthquake, and shortly thereafter a really freaking big wall of sea water. Certain I read that somewhere. No excuses for lying afterwards. Can't regulate mother nature, she'll kick you in the jimmy every time. LIke it or no, nuclear is still the safest and cleanest way to go.
        • by tp1024 (2409684) on Thursday November 03, 2011 @03:07PM (#37938904)
          In the case of Fukushima Daiichi at least, the issue was indeed lack of regulation actually put in place - long before the accident. http://www.interaksyon.com/article/9480/fukushima-long-ranked-most-hazardous-plant [interaksyon.com]
        • Nuclear is probably the most regulated industry in the world. You do realize the issue was not caused by lack of regulations.

          Which strongly suggests that we do not have the beginnings of a clue about how to build a safe and environmentally sound nuclear power industry.

          There are no technical problems with using nuclear fission as a power source. There are clearly problems with using human beings to design, operate, and maintain such power plants. Failure of those components is what the regulations are supposed to protect us against, but clearly we do not yet know how to solve that critical part of the problem.

          If we had any sen

          • by Jeremi (14640)

            If we had any sense at all, we would shut down every nuclear power plant until we had evidence that we had developed human beings who are smart enough to run them properly without ever screwing up.

            Or, slightly more realistically, until someone comes up with a design for a fission power plant that can be completely mismanaged, neglected, even bombed, and still not cause a significant radiation problem.

            Dunno if that's feasible (short of developing nuclear fusion and using that instead), but it would be one way to go.

      • Want to conserve energy? Increase rates.

        You are part of the rebel alliance and a traitor! [youtube.com]

      • by zmooc (33175)

        A natural gas plant? So sad.

        An unfinished fast breeder reactor near where I live was turned into an amusement park;-)

        http://www.wunderlandkalkar.eu/en/ [wunderlandkalkar.eu]

    • by shish (588640) on Thursday November 03, 2011 @01:24PM (#37937280) Homepage

      my enthusiasm also assumed that the industry was regulated and transparent enough to be safe. Clearly it is not

      And other industries are?

      Burning coal does far more, further reaching damage - it just does it slowly and constantly as part of normal operating procedure, so nobody cares. (Other sources like solar / wind would be best, but I don't see them being able to fill the whole planet's energy needs any time soon)

      • by couchslug (175151)

        "Burning coal does far more, further reaching damage"

        Dispersed casualties are easy to manage as they can be dealt with by existing care and disposal systems. That's much less disruptive than the shock of sudden local events.

      • (Other sources like solar / wind would be best, but I don't see them being able to fill the whole planet's energy needs any time soon)

        Why not? Solar supply has been increasing at 10x per decade and is expected to meet cost parity with other forms of supply this decade. Wind power has the fastest ROI of any energy supply. The constant supply argument is false, there are plenty of energy storage technologies with efficiencies of up to 90%+, they just need further investment.

        Whilst the insane energy hog that is USA might have difficulty running completely from renewables, I don't think the rest of the world would have a problem.

        Why waste tim

    • Re: (Score:3, Insightful)

      Fission is a zero-carbon system.

      In other news, apples are a zero orange food...

      • by arkenian (1560563)

        Fission is a zero-carbon system.

        In other news, apples are a zero orange food...

        While I agree with your point (That is to say, that the damage from Fission is not carbon-based but clearly still exists) I will point out that the difference is that fission and carbon fuels output in the same way. I can measure the output of both on the same scale, whereas when I try to measure the flavor of an apple in units of "citrusy goodness" people look at me funny.

        • The difference is that fossil fuels do damage during normal operations due to the CO2 and other emissions.

          Nuclear (generally) does it's damage when something goes wrong.

          You can plan for and mitigate the former, you can't plan for and mitigate disaster on the level necessary for nuclear. When a coal plant blows up, it just blows up and you go right back in and rebuild. We just choose not to plan for and mitigate the normal operation aspects of coal.

          - yes I know nuclear waste is an issue but agai
          • by arkenian (1560563)

            You can plan for and mitigate the former, you can't plan for and mitigate disaster on the level necessary for nuclear. When a coal plant blows up, it just blows up and you go right back in and rebuild. We just choose not to plan for and mitigate the normal operation aspects of coal.

            See, that's where I disagree. I mean, we build dams. Do you have any idea what would happen if Hoover dam were to collapse?? You CAN plan for and (to some degree) mitigate disasters. That said, the primary prerequisite for this is honesty, and I"ll admit that the fuukushima incident was depressing largely in the sense that honesty seemed to be lacking. Without honest risk assesments you can't do anything (granted an honest risk assessment is not the same as a wholly accurate one, but any honest risk a

            • I mean, we build dams. Do you have any idea what would happen if Hoover dam were to collapse?

              If Hoover dam collapsed, I could quite safely go there the next day with absolutely no worries to my health. Besides this [howstuffworks.com] really doesn't seem to indicate there would be massive loss of life...which itself could be mitigated by moving a few towns uphill maybe 30 feet? Not insignificant, but down river from Hoover isn't exactly heavily populated. The most significant damages would be in the loss of the electric and irrigation water which is a far different thing than dying due to radiation.

              Dams general

    • by khallow (566160)
      Could you point me to a source that describes these lies?
    • by gstrickler (920733) on Thursday November 03, 2011 @01:34PM (#37937452)

      Judging nuclear power's safety by a first generation reactor design that was built nearly 40 years ago, and that despite a M9 earthquake and 15m tsunami has not killed anyone, and is predicted to eventually cause up to 100 deaths from cancer is foolish. It's like judging hydro power by the dams that have burst and flooded and killed thousands, or by natural gas pipeline explosions that have killed hundreds, yet you're not protesting those types of power.

      Nuclear power has caused fewer deaths per TWh [nextbigfuture.com] generated than any major power source, including wind, solar, geothermal, hydro, or fossil fuels. Nuclear power is the safest power source yet tried, and that's even with the older reactor designs and the Russian RBMK design (e.g Chernobyl) that is inherently unstable and should never have been built.

      Gen III reactors have passive safety designs that allow full cold shutdown with no external power. And thorium fueled reactors don't produce usable quantities of plutonium so they're not a proliferation concern, and doesn't require uranium enrichment (which is itself expensive and dangerous). And using fuel reprocessing dramatically lowers the nuclear waste (by a factor to 10 to 100).

      • by trout007 (975317)

        Heavy water reactors don't need enriched uranium as fuel either.

        • True, but they still produce plutonium, and the energy and cost to extract sufficient heavy water for the reactor is significant, and you have the ongoing problem of removing tritium from the heavy water. Because of these factors, HWR are probably not a good long term solution.

      • by Solandri (704621) on Thursday November 03, 2011 @03:39PM (#37939394)

        Judging nuclear power's safety by a first generation reactor design that was built nearly 40 years ago, and that despite a M9 earthquake and 15m tsunami has not killed anyone, and is predicted to eventually cause up to 100 deaths from cancer is foolish. It's like judging hydro power by the dams that have burst and flooded and killed thousands

        The worst power generation-related accident in history was the cascade failure of a series of hydroelectric dams [wikipedia.org]. It killed nearly a quarter million people, damaged or destroyed 6 million buildings, and forced the evacuation of 11 million residents. Basically, it was as bad as or worse than the tsunami in Japan.

        In stark contrast to nuclear accidents, it is almost never brought up as an argument against hydroelectric power.

        • by hyperizer (123449)

          The worst power generation-related accident in history was the cascade failure of a series of hydroelectric dams [wikipedia.org]. It killed nearly a quarter million people, damaged or destroyed 6 million buildings, and forced the evacuation of 11 million residents. Basically, it was as bad as or worse than the tsunami in Japan.

          In stark contrast to nuclear accidents, it is almost never brought up as an argument against hydroelectric power.

          A "once-in-2000-years" year flood is going to cause casualties whether there are hydro turbines there or not. At least that area isn't uninhabitable for centuries.

        • Regarding the 1975 Dam catastrophe... Wikipedia is entirely too polite on the Chinese government's culpability in the disaster, and what happened to hydrologist Chen Xing, who warned that the dam's design was inadequate [sjsu.edu], recommending 12 sluice gates instead of the 5 implemented.

          For his criticism, he was over-ridden by party officials and exiled to the western provinces.

        • by Guppy (12314)

          Following up, I'd recommend the following book, which contains an account of the disaster in Chapter 3:
          The river dragon has come! [google.com] by D. Qing, J. Thibodeau, & P. B. Williams.

      • by dachshund (300733)

        Judging nuclear power's safety by a first generation reactor design that was built nearly 40 years ago, and that despite a M9 earthquake and 15m tsunami

        I think the objection is that the reactor was still operating, despite the fact that it was 40 years old, past its design lifetime, and wasn't rated to handle an event that would occur with relatively high probability in the reactor's lifespan.

        In other words, it's everything the previous posters have said: bad management by a for-profit company. It doesn't r

        • 1. It wasn't past it's design lifetime. The reactors were each 35-40 years into a 40 year initial license (but only 25-30 years since first criticality). With a design lifetime of at least 50 years.

          2. It was designed for a maximum of a magnitude 8 quake. A magnitude 8+ earthquake did not have "a relatively high probability" in it's lifetime when it was built. There is an average of 1 per year [usgs.gov] worldwide, 81% of those [wikipedia.org] along the 40,000km "ring of fire". That does not translate into a "relatively high probabili

    • by Anonymous Coward on Thursday November 03, 2011 @01:36PM (#37937500)

      So you stopped being a proponent because:
      1) A seriously outdated nuclear power plant has some problems after it is hitten by an earthquake and a tsunami that would level to the ground any american city;
      2) The specific company that owned the plant lied about security in case of an tsunami of that scale;
      3) You are ignorant of the past 30 years of advancements in nuclear power generation;
      4) You are ignorant of what negative temperature coeficient of reactivity means;

      Welcome to the world where advanced technology is stopped by idiots that can't and don't want to understand it.

      • thanks
      • by sharkey (16670)
        That's an awfully wordy way to say "Liberal".
        • Nothing wrong with being liberal. Nothing the OP said fits the definition of liberal, so please stop misusing the word.

          Liberal [reference.com] - adjective
          1. favorable to progress or reform, as in political or religious affairs.
          2. (often initial capital letter) noting or pertaining to a political party advocating measures of progressive political reform.
          3. of, pertaining to, based on, or advocating liberalism.
          4. favorable to or in accord with concepts of maximum individual freedom possible, especially as guaranteed by law a

      • by jbengt (874751)
        So you are still a proponent even though:
        1) Previously constructed plants will always seem outdated compared to more current ones (in the future, this will include plants now undergoing planning) - and the industry is lobbying to keep open plants that have outlived their originally intended lifetimes. And the earthquake and tsunami were at a level known to happen in the area in the past.
        2) The specific company that owned a plant lied about things that might affect its' bottom line, as all companies are w
    • Don't get down on nuclear. Thorium is the future. We have enough supply of it to replace the entire world's energy needs, and the salt based solution is the safest there is. It does not require the reinforced meltdown containment of traditional nuclear.

      If any nuclear power could be called safe, Thorium is it. Or LFTR, specifically.

      https://plus.google.com/u/1/107403602702342125509/posts/VFLzb7rzByx [google.com] - All about Thorium and the WH.gov petition link.

    • I fully agree and can relate.

      I just wanted to add that it was interesting timing for this announcement, as it came right after the first reactivation of a Japanese reactor since the Fukushima accident [mainichi.jp].
    • How many people have died from this incident (or any nuclear-related event) compared to number of coal miners and oil rig workers who are killed each year? As far as long term health effects, like increased cancer rates, time will tell. However, let's compare that to coal miners contracting chronic lung disease and that the many deaths attributed to respiratory distress caused by air pollution. What about coal mine explosions or oil spills? Please explain to me how nuclear power is somehow more dangerou
    • by Jawnn (445279)

      I was a proponent of expanding nuclear fission electricity generation until Fukushima. Fission is a zero-carbon system and cheap at massive scale, if you can manage to keep the government regulators off your back with all their useless "safety" requirements.

      TFTFY.

    • by trout007 (975317)

      So should we stop the reactors that make the arterial used in nuclear medicine? That way when we shut down all reactors cancer deaths will increase.

  • by Anonymous Coward on Thursday November 03, 2011 @01:39PM (#37937536)

    Colder water increases the chance of a criticality. Colder water is denser, therefore a better neutron moderator. As the temperature in the core drops, it probably crossed the threshold for a (briefly) sustained reaction, which probably then melted or reformed into a shape no longer capable of sustaining the reaction. As the shape and condition of the fuel is currently a complete unknown, this could happen again at any time until all the way down to room temperature. /former US Navy reactor operator

    • The density change in liquid water does not significantly alter it's ability to moderate neutron flux. It's only when the water is hot enough that some of it vaporizes that it's ability to moderate neutron flux changes significantly. Therefore, that part of your statement is materially incorrect, even though it is technically correct.

      The shape, and current status of the fuel is unknown, and that alone is the likely source of this event.

  • Not too surprising (Score:5, Informative)

    by Animats (122034) on Thursday November 03, 2011 @01:48PM (#37937692) Homepage

    Down at the bottom of Reactor 1, they have a melted core. It's not surprising that they have a criticality event once in a while. Nobody seems to have a clue how to get in there, remove the core bit by bit, and transport the mess in small pieces to some disposal location. TEPCO is saying that in 10 years, they might be able to start on that. Meanwhile, they have to continuously remove about 2MW of heat or things get worse.

    One bright spot in this is that the plant is built on bedrock, and the containment vessel seems to have held. It needs to hold for another decade or two.

    • One bright spot in this is that the plant is built on bedrock, and the containment vessel seems to have held.

      At least one of them didn't, hence all the iodine and caesium isotopes spreading over a large area. From what I've read it's pretty certain that reactor 2's containment failed, the status of the others is less clear.

    • by Mike_K (138858) on Thursday November 03, 2011 @03:52PM (#37939580)

      Meanwhile, they have to continuously remove about 2MW of heat or things get worse.

      I wonder if they could use that extra heat to generate some electricity...

      • by iksbob (947407)

        Maybe if the containment vessels and/or cooling systems were intact. But then if that were the case, this wouldn't be such a significant nuclear disaster since all the radioisotopes and such would still be contained on-site.

  • by goffster (1104287) on Thursday November 03, 2011 @01:53PM (#37937780)

    One of the best inventions for a train was its braking system.
    You have to apply energy to *prevent* a train car from braking.
    This prevents run-away cars.

    A successful nuclear reactor would have something similar
    where you have to apply energy to keep the coolant at bay.

    i.e. The core is at the bottom of the ocean and energy
    is spent by the reactor to keep ocean water from rushing in.

    • That's been tried. One GE design had huge blocks of ice with boron as an emergency cooling system. Sequoyah Nuclear Generating Station in Tennessee uses that technology. It's not considered a good idea any more. There's a finite supply of coolant, but the waste heat from the reactor keeps on coming.

    • by djl4570 (801529)
      A passive cooling system based on convection has already been designed and could have been installed on these reactors if TEP had chosen to spend the money. Your proposal as written could cause a cold water excursion. Cold dense water moderates more neutrons to energy levels that cause fission. Hot less dense water moderates fewer neutrons. In a reactor at equilibrium where the heat is being removed at the rate it is being generated, any abrupt change in the temperature of the core will change the
    • by radtea (464814)

      A successful nuclear reactor would have something similar where you have to apply energy to keep the coolant at bay.

      To take the train analogy properly, imagine you replaced your typical coal-fired or diesel-electric train with one that moved 100 times faster. Any reasonable braking technology could be overwhelmed by this, and this is the problem with nuclear power: the energy density in the core is phenomenally high, resulting in it being able to overwhelm any reasonable level of passive cooling.

      A 2 MWth coal-fired power plant burns a box-car of coal every fifteen minutes. A comparable nuclear power plant is refueled

  • Call me when they detect nuclear fusion.
  • by e3m4n (947977) on Thursday November 03, 2011 @02:24PM (#37938254)

    As a former navy nuclear enlisted personnel; I can tell you that reactors operate at criticality all the time. The mere definition of critical is when all the thermal neutrons born from fission go on to cause more fission reactions. Critical = steady state. 'Prompt critical' or 'supercritical' is when its critical without the contribution of thermal (delayed) neutrons.

    Every single reactor startup, we calculate exactly what rod height we expect to reach when the reactor goes critical. Once we are critical we then allow steam demand and thermal coolant temperature to drive reactor power output. higher temps are less dense thereby thermalising fewer neutrons lowering reactor power. If steam demand or load increases coolant temperature subsequently lowers making the coolant more dense in turn thermalising more neutrons increasing reactor output. Its all driven back to steady state. This is commonly referred to as a negative reactivity coefficient. Critical = steady state and Steady state is a good thing.

    • by jittles (1613415)

      Critical = steady state and Steady state is a good thing.

      Not trying to argue with you about this, but in this case they do not have any (or much) control over the reactor. Having it continue to produce a reaction is likely an undesirable condition.

  • No worries, this is all perfectly safe. Or so I've been told on slashdot.
  • by Mt._Honkey (514673) on Thursday November 03, 2011 @02:44PM (#37938578)

    This article confuses me a great deal, and IAANP (grad student). They say "one hundred thousandth of a becquerel per cubic centimeter of xenon-133 and xenon-135 was detected in gas samples.", that means one decay per second in every 1/10 of a cubic meter. This is a very low rate. U-238 undergoes spontaneous fission in about 1 in 10^5 radioactive decays whether it is in a reactor or not,and about 1% of those fissions produces a Xe-135 (either directly, or after decay of one of its parents like I-135). If I do a back of the envelope calculation, I find that for 10 tons (a guess) of U-238 sitting there being nice, about 100,000 Xe-135 will be produced every second. Thus, unless the air volume they are sampling from is much larger than 10,000 cubic meters, this sounds like what I would expect WITHOUT criticality.

    Am I missing something here?

Nothing is rich but the inexhaustible wealth of nature. She shows us only surfaces, but she is a million fathoms deep. -- Ralph Waldo Emerson

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