Meltdown

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  • Rating - 100%
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    Mar 17, 2009
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    Dyer
    I know this is part of the thread on the aftermath of the Japan earthquake, but I think it now deserves it's own thread.

    Japanese officials are know acknowledging the possibility of nuclear meltdowns in at least 2 of the reactors in the Fukushima prefectre.

    A meltdown in a worst case scenario could affect the mainland United States, if not the world. Just talking worst case scenario here, if one of the reactors were to breech it's containment vessel a cascade of events could happen that would make Chernobyl look like Three Mile Island in comparison. Say the core were to meltdown and release massive amounts of radiation. The resulting reactors at the site which are also in trouble might also have radiation levels too high for humans to survive for more than a short amount of time. Even if brave souls were to stay behind they might not survive for more than a few hours. They would be incapacitated and unable to work in a very short time. This could cause the whole plant to be evacuated. If one of these reactors were to runaway and melt through the bottom of the facility and continue to sink until it hit ground water (or ocean water) the resulting steam explosion would destroy the rest of the complex and be much like a nuclear explosion on a massive scale.

    The effects would be devastating to the world. Keep in mind, a 1GW nuclear reactor harnesses the energy of a Hiroshima size nuclear bomb every 6 hours. They have enough fuel to keep up this energy production for a year. If the hundreds of tons of nuclear fuel were dispersed we would have a global catastrophe. The immediate area would be uninhabitable virtually forever. What would happen to the rest of the world is unknown. These plants are right on the ocean. Assuming the winds normally blow from west to east that would carry the fallout over the ocean. What would happen to the ocean? What would happen to the US?

    I have a hobby type interest in nuclear power and understand how things work. What I don't understand is what could happen in a worst case scenario. Anybody here have any thoughts?
     

    longbow

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    3   0   0
    Apr 2, 2008
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    oh crap!!!! she blew, now we wait to see what happens. Radiation leaks confirmed.

    capt.de6524c5e75846f49f74dcc348ce18d1-de6524c5e75846f49f74dcc348ce18d1-0.jpg
     
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    Mar 17, 2009
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    Dyer
    Don't worry about that explosion. The media says that everything is going to be just fine. Heck, even if they have a complete and total meltdown it will only affect people in a 6 mile radius.
     
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    Mar 17, 2009
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    Dyer
    The explosion that you saw was caused by the pumping system, not the reactor. They have resorted to pumping seawater into the reactor. These guys lie worse than Obama.
     
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    Mar 17, 2009
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    Dyer
    Officially released radiation levels of 866 nGy have been released. That means at this point workers onsite can only stay there for 34 hours before receiving a lethal dose of radiation. There is nothing to see here, move along please.
     

    Leadeye

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    Jan 19, 2009
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    Looking at the film I would think that the explosion was hydrogen/oxygen more than a steam release from something breaking, it's a pretty sharp pop on film. Hydrogen generation will be coming from extremely hot metal reacting with water which tells me that they are probably facing a partial meltdown/softening already. In a boiling water reactor your turbines are in the hot loop as the steam comes from the water in the reactor being used as both coolant and moderator. With the reactor overheated hydrogen may have been carried out of the reactor vessel and the explosion taken place downstream rather than in the vessel itself. Flooding the containment with seawater sounds like they can't control the feedwater any more or more ominously that the explosion was in the reactor vessel rather than downstream. Either way that unit is finished.
     
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    Mar 17, 2009
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    Dyer
    And what are they going to do with the irradiated seawater? You have to have a way to exchange the energy out of the water. That mechanism already looks like it went up in smoke. So you pump seawater into the reactor, then what? What do you do with the heat that builds into the seawater. They are going to have to build a whole new cooling system from my estimation?
     

    longbow

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    Apr 2, 2008
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    All good points, invest in robot companies!

    Superheated water turning to steam does crazy stuff, but I keep looking at the shockwave and something else made her pop!
     

    longbow

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    Apr 2, 2008
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    Are there any pictures taken directly above the unit looking into it. That will be the most telling part.

    They are now detecting isotopes that show the rods were exposed to air and/or are melting down ( could be a partial meltdown)
     

    Tryin'

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    Nov 18, 2009
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    What is the difference between a light water reactor and heavy water reactor concerning meltdown? Officials are claiming that a Chernobyl event is impossible due to the light water reactor used.
     

    Leadeye

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    So, if the reactor hasn't been compromised how did the hydrogen get out?

    The claim is that the explosion came from vented steam mixed with hydrogen. Venting must have ignited inside the containment building rupturing it.

    The big issue in a meltdown is the change in geometry of the nuclear fuel in the reactor core. When the structure softens and slumps it's anybodys guess how the fuel geometry will change, control rods in these reactor come in from the bottom and may move if the supporting structure fails. More water will act as a moderator and may increase the reaction if the geometry is changed or control rods are out of position.

    They will get this mess cleaned up over time, but nuclear power in this country is finished once again. I watched my career evaporate overnight after TMI was on TV 24/7.
     
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    Mar 17, 2009
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    Dyer
    So are you saying that they vented the steam from the containment vessel into the non containment part of the reactor building? Why wouldn't they just vent that directly to the atmosphere? Wouldn't the explosion have ruptured feed lines into/out of the reactor? I would think that an explosion of that magnitude would have damaged at least some means of controlling that thing.
     

    Leadeye

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    Jan 19, 2009
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    So are you saying that they vented the steam from the containment vessel into the non containment part of the reactor building? Why wouldn't they just vent that directly to the atmosphere? Wouldn't the explosion have ruptured feed lines into/out of the reactor? I would think that an explosion of that magnitude would have damaged at least some means of controlling that thing.

    Procedure usually dictates venting inside the containment first, allows the short half life stuff to decay. You're right, those lines are probably gone now or they would not be pumping the seawater in. They lost control of the reactor before the explosion as they could no longer circulate water through the reactor vessel which caused the temeprature to go up. The fact that they are filling the containment building with water would indicate to me that the reactor vessel is damaged.

    The TMI event was really more of a non-event as everything was contained. Cleanup took a long time and they lost the unit forever. The USSR has a long string of really bad nuclear disasters other than Chernyobyl. At one time there was a lake near Chelyabinsk callled lake Karachey which was used as an open circuit cooling pond for plutonium production reactors. You could stand on the shore and be dead in less than half an hour.
     

    Leadeye

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    What is the difference between a light water reactor and heavy water reactor concerning meltdown? Officials are claiming that a Chernobyl event is impossible due to the light water reactor used.

    Chernoybl was a graphite moderated reactor, water was used almost exclusivly as coolant/steam generation. This type has what is called a "positive void coefficient" when the water runs out the reaction speeds up some. Light water reactors are the opposite, you need the water which acts as the moderator in them to keep the reaction going. The power spike at Chernoybyl vaporized all the water in the reactor increasing the reaction rate even more. The reactor at Chernobyl then caught on fire which created the worst of the problem. A good read on this is the book Ablaze by Piers Read I think. The amount of courage in some of the people involved is amazing, as is some of the stupidity.
     
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