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Japan

Fukushima Meltdown Might Have Come With Earthquake, Not Tsunami 172

Posted by timothy
from the but-the-tsunami-helped dept.
formfeed writes "As the data from the Fukushima reactor is being reviewed it looks like the meltdown happened much earlier: '[T]he fuel rods in the No. 1 reactor were completely exposed to the air and rapidly heating five hours after the quake.' Apparently, the earthquake had caused a crack in the containment vessel. Which means, that even without the generators failing, the meltdown might still have happened. With this new data, it seems a similar incident could happen in an earthquake zone even without a tsunami."
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Fukushima Meltdown Might Have Come With Earthquake, Not Tsunami

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  • by borrrden (2014802) on Wednesday May 18, 2011 @05:23AM (#36163566)
    Nowhere in TFA does it say that the earthquake caused the damage to the reactor that led to it melting. Also, I doubt it is even possible for it to melt in the 40 - 50 minutes it took for the tsunami to arrive. It first has to evaporate or otherwise evacuate the water inside the reactor, and then heat up to about 2800 C to melt. What the article is saying is that the rods had melted much sooner than initially thought. The timeline changed, not the reason. They are also looking into possible complications that may have occurred in the initial hour (there is another report that the cooling systems were manually shut off after a pressure drop, as per the instructions for such a scenario), but nowhere does it suggest that the earthquake, and not the tsunami, caused the crisis. The closest it comes to that is saying that the earthquake may have "damaged" the reactor, but gives no speculation on the effect that it would have had on the cooling system. A crack in the containment vessel without any cracks in the reactor pressure vessel would not have been an issue.
  • Re:Uh... summary? (Score:2, Informative)

    by Sollord (888521) on Wednesday May 18, 2011 @05:26AM (#36163572)

    Welcome to /. leave facts at the door along with all thoughts of compromise as your solutions and knowledge are always right on all topics

  • Battery Power (Score:5, Informative)

    by mdsolar (1045926) on Wednesday May 18, 2011 @06:45AM (#36163880) Homepage Journal
    There is a detailed diary here: http://online.wsj.com/article/SB10001424052748703509104576330531564264132.html [wsj.com]

    "Documents released by Tepco Monday showed the isolation condenser— an emergency cooling system installed on Reactor No. 1 before the quake as a final resort in case of a total loss of power—worked only sporadically, if at all. Tepco officials explained that somebody appears to have manually closed the valves on the condenser soon after the March 11 quake—but before the tsunami hit about an hour later—to control the fluctuating pressure inside the reactor. Reopening the valves required battery power, so those valves likely couldn't be opened because the tsunami damaged the backup batteries.

    If the valves hadn't been shut, things might have turned out differently. Temperatures in the reactor climbed faster than initially expected, causing more and faster damage. Tepco admitted this week the problems at Reactor 1 were far worse than originally thought. Its new projection shows fuel may have started melting rapidly only five hours after the March 11 quake. By 6:50 a.m. March 12, the fuel was likely in a heap at the bottom of the vessel. "

    Battery power was lost apparently.
  • by DrBoumBoum (926687) on Wednesday May 18, 2011 @07:50AM (#36164100) Journal
    No, the batteries provide nowhere near the power required by the cooling system, this was explained on slashdot a few weeks ago by a guy working with the pumps (sorry no time to find the comment now). The cooling system consumes a large amount of the total electrical output of the plant (something between 10 and 20 percent, again from memory), no battery setup can provide this amount of energy. The batteries are only used to power the instrumentation and control mechanisms (valves etc).
  • by Fierlo (842860) on Wednesday May 18, 2011 @08:03AM (#36164150)
    Except that decay power is about 7% or so right after shutdown. I'm not entirely sure where you got the 10 MW thermal. Unit 1 is a 480 MWe reactor. If you generously assume a 50% efficiency (it wasn't)...

    480/0.5*0.07 = 67.2 MW thermal

    More likely it's in the mid 30s (or even low 30s) for efficiency, so you end up around 96 MW thermal immediately after shutdown.

  • Re:Uh... summary? (Score:4, Informative)

    by ozmanjusri (601766) <aussie_bob@@@hotmail...com> on Wednesday May 18, 2011 @09:24AM (#36164804) Journal

    [reactors...] breached containment. [citation needed]

    'Engineers from the Tokyo Electric Power company (Tepco) entered the No.1 reactor at the end of last week for the first time and saw the top five feet or so of the core’s 13ft-long fuel rods had been exposed to the air and melted down.
    Previously, Tepco believed that the core of the reactor was submerged in enough water to keep it stable and that only 55 per cent of the core had been damaged.
    Now the company is worried that the molten pool of radioactive fuel may have burned a hole through the bottom of the containment vessel, causing water to leak.
    “We will have to revise our plans,” said Junichi Matsumoto, a spokesman for Tepco. “We cannot deny the possibility that a hole in the pressure vessel caused water to leak”.'

    AFAIK, all the "leaking radioactive material" stories are about the spent fuel pond(s) not the reactor cores.

    Leaking?

    "United States government engineers sent to help with the crisis in Japan are warning that the troubled nuclear plant there is facing a wide array of fresh threats that could persist indefinitely, and that in some cases are expected to increase as a result of the very measures being taken to keep the plant stable, according to a confidential assessment prepared by the Nuclear Regulatory Commission."

    "The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed."
    http://www.nytimes.com/2011/04/06/world/asia/06nuclear.html?_r=2&hp [nytimes.com]

  • Re:Uh... summary? (Score:2, Informative)

    by Anonymous Coward on Wednesday May 18, 2011 @12:36PM (#36167516)

    This was a big deal - level 7 nuclear disaster.

    That's a fairly useless scale ( read up [wikipedia.org] on the "criteria").
    This is worse than TMI (which had barely measurable radioactive release), but nowhere near as bad as Chernobyl (AFAIK, so far).
    Chernobyl had no sealed containment vessel, and the fuel was allowed to reach super-high temperatures which burned the graphite moderator directly into the atmosphere, where wind carried it for miles - which is REALLY REALLY BAD.

    The containment vessel was breached.

    Again, [citation needed].
    See my links and quotes in this post. [slashdot.org]

    The spent fuel rods became radioactive because their pools became depleted.

    The spent fuel rods are always radioactive (at least until they decay according to the half-life of their fuel).

    Plutonium has been leaking into the sea.

    Plutonium? You sure it wasn't cesium or iodine?
    Still radioactive, but not nearly has bad as Pu.
    I can find a few links stating that plutonium has been found "outside the reactor building", but they don't got into much detail on the amounts.

    Please provide a link if you've got one, it's hard to find unbiased info.

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