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Explosion at Japanese nuclear plant

Discussion in 'General' started by RichB, Mar 12, 2011.

  1. cgordon3

    cgordon3 I need a new bike...

    That was a great link.
     
  2. JCP636

    JCP636 Well-Known Member

    yea, seriously. Now I know how to cool down a nuclear reactor, haha
     
  3. Motofun352

    Motofun352 Well-Known Member

    Boron (specifically Boron-10) is a "poison" in that it has a very high cross section for thermal nuetron capture. It is effective at shutting down the nuclear fission reaction. HOWEVER, I seriously doubt that that the core was critical during these events. I am guessing that they scrammed the reactor(s) shortly after the the earthquake thus shutting the fission process down. Adding Boron now just helps assure that a recriticality doesn't occur, it doesn't do squat for cooling. Adding seawater to the core does mean that the plant is totally screwed and will never be recovered, though that was highly unlikely anyways.
    They are struggling with decay heat. This is the heat given off by the radioactive decay products contained within the core. It must be removed, just like any other machine, or the temperature will increase to unacceptable levels. To remove the decay heat there are systems of pumps and heat exchangers that are used for the purpose. If these systems are destroyed or unable to perform, the next best thing to do is to relieve the pressure that builds up, in a controlled manner so that the reactor vessel and or the primary containment remain intact. This is done by adding water and blowing off steam. The risk is there is a significant amount of Hydrogen to deal with. This hydrogen is the result of radiolysis of the water. I believe this is the source of the explosions that have occurred.
    Things are definately not good at these plants. They will be a mess for years to come, though I still doubt that there will be large scale release. The corporation (TEPCO) is screwed though.
     
  4. Inquizid

    Inquizid Member Well-Known

    They just reported that the fuel rods are now exposed:confused:
     
  5. Silo Pete

    Silo Pete We have ignition.

    For me, everything would come full circle if Godzilla appeared. I mean really, what else can happen.
     
  6. sdg

    sdg *

    couldn't herp it.:D
     
  7. LabRat

    LabRat Well-Known Member

    Cold water accident is what you would be talking about. However this reactor would be a low enrichment BWR, a completely different animal from the Navy PWRs, and thus the japan reactors have a different alpha-T. So their temperature coefficient of reactivity, would mean colder is better. I would hope that the rods hit the bottom, and the reactor was poisoned out with rods, and at this point was just a big hot rock and this is just a management of decay heat. If they were slowly injecting cold salt water and not "Dumping" the seawater it would accomplish the cooling. I can't think of a reactor design that would allow a super large quantiy of water to get 'dumped' in. I don't have much BWR knowledge, but think part of the issue is that as it was not at the pressure that a PWR was at, as the steam bubble builds up it does funky stuff with the pressure causing different boiling, would have to look at the curves again, but they needed to vent steam to reduce pressure to get more heat out.
     
  8. Jed

    Jed mellifluous

    How would a pebble bed reactor handle a situation like this?
     
  9. LabRat

    LabRat Well-Known Member

    More I think about it is is possible that they were not adding salt water to the 'primary', and they were adding salt water to the containment 'pool' that the primary was sitting in. That would draw some heat away from the pressure vessel cooling the plant. So they could dump water here pretty easily, as that system is just there to regulate some heat and slow down escaping zoomies.
     
  10. Lawn Dart

    Lawn Dart Difficult. With a big D.

    I'm so glad I didn't press Submit on the reply I'd crafted before reading the entire thread... I saw "volcano" earlier and immediately thought of two things - Godzilla and the Sim City computer game I'd played as a kid.

    I'm with you... If giant mutated Lizards and Moths show up, I think it will be the beginning of the end...
     
  11. cgordon3

    cgordon3 I need a new bike...



    THe link from above seemed to indicate that very thing. Keeping the pool of water full, and venting off the steam to keep the core from being exposed to the air.

    The reactor itself will probably have to be decommissioned after all this, but at least they will be able to dissipate the decay heat, and keep the thing from Meltdown...
     
  12. tony 340

    tony 340 Well-Known Member

    I was talking to a buddy Saturday night about this.

    If this went down in Detroit, damn I can't even imagine how people would be.
     
  13. RCjohn

    RCjohn Killin machine.

    As soon as the seawater and boric acid hit the core the cores were ruined. Though if they did actually have partial meltdown they were ruined anyway but of course this is the least of their worries right now. If the explosions were hydrogen explosions then it is a partial meltdown since that's one of the results of meltdown.

    This reactor disaster isn't even close to the disaster that Chernobyl was so that's good. From a human health standpoint this Japanese nuclear incident isn't a huge problem for the public. The employees are at some danger while responding but the public should be impacted significantly from a radioactive standpoint.

    And as silly as it sounds, the hydrogen explosions are a self protective measure. When it happens it releases pressure and temperature via the primary reliefs and relieve into the secondary containment which isn't too bad if the secondary containment is intact... typically. When they are really bad the secondary containment can't retain all of the pressure then it is breached if you don't vent it. The bad part is the venting/release allows contaminated steam out to the atmosphere.
     
    Last edited: Mar 14, 2011
  14. Steeltoe

    Steeltoe What's my move?

  15. Mongo

    Mongo Administrator

    Makes sense to me. I find it funny though that all of the people who like freaking out will keep ignoring the exposure levels being low.
     
  16. RCjohn

    RCjohn Killin machine.

    It says less than the equivalent from month of natural background. Your lantern mantels would be more harmful. :D

    My guess is the air monitors in the plant started showing elevated levels and since it's reactor fallout you don't want that one the ship because you can't distinguish between the carrier's contamination and the Japanese. Basically it's easier and less paperwork to just move out a little. :up:
     
  17. Steeltoe

    Steeltoe What's my move?

    Moreso because the reporter I'm following is having a hard time getting a straight answer. We'll see when he gets there.

    PS: He just got confirmed to embed with the Navy in Japan.
     
  18. Silo Pete

    Silo Pete We have ignition.

    While nothing is impossible, I do not see any direct threat to the U.S., even from a major release. A plume would require upper-atmosphere suspension to travel that distance. The upper atmospheric wind currents alone would dilute the concentration to levels that would be negligible, by the time it reached the shores of the U.S.

    The only impact to the U.S. I can imagine would be from indirect transfer of contaminated objects, from humanitarian effort, or some sort of re-suspension from ships or cargo, in my humble opinion of course.
     
  19. RCjohn

    RCjohn Killin machine.

    I was surprise when Chernobyl fallout got to Canada and Upstate NY. :eek:
     
  20. stan.riner

    stan.riner Well-Known Member

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