~~~ashima reactor meltdown.
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    Default ~~~ashima reactor meltdown.

    Panic limitation, been reading the news and had a drunken argument last night regarding what's going on with the ~~~ashima Daiichi reactor site.

    First off some low brow physics lessons.
    A nuclear reactor is a very simple device, think of it like a high pressure beer keg (only on a far larger scale)
    This is called a pressure vessel (its under enormous pressure for the majority of the time)
    This is housed inside another vessel called the primary vessel.
    Think of a beer keg inside a nice concrete and lead case.

    Inside the beer keg is water, its filled up with the stuff and there's a steam pipe coming out the top and a water pipe coming in to refill the boiled off steam.
    The steam pipe connects to big motors which produce the electricity then to the cooling system then back to the pressure vessel. everything is contained in one big loop.

    Now there's two types of rods in the water, Fuel Rods, made from uranium pellets housed in zirconium. then Control Rods made from boron.
    The fuel rods are radioactive the control rods aren't, its their job to absorb neutrons and control the reaction (they become radioactive through their lifespan by this absorption)
    take your hand and open your fingers like your sign languaging four, these would be Fuel Rods, now do the same with the other hand and place it over the top interwoven with the four and you get the idea of how things work, drop the control rods lower the reaction slows, take them back up and the reaction speeds up.

    The Fuel rods decay and give off some heat and neutrons.
    If the radioactive material gets struck by a neutron it splits at an atomic level and gives off two more neutrons and more heat, these two neutrons hit other rods and cause the atoms in them to split and you wind up with 4 neutrons and even more heat, then 8,16,32,64,128,256,1024,2048 and so on.
    This happens very quickly doubling again and again till the reactor goes bang like a nuclear bomb.
    Hence the control rods which take neutrons away from the fuel rods and stop things happening too quickly and getting too hot.

    Thats all a reactor does, day in day out, its as simple as that!
    If something starts to go wrong you simply drop all the control rods down and the reaction effectively stops because the bulk of the neutrons flying around are absorbed.

    So WTF is the big deal?
    When a disaster happens this is what happens, and its exactly what happened in Japan, the rods dropped and the reactors went into sleep mode.
    Crisis averted...
    Mostly...

    The real problem is that if you strike a uranium atom with a neutron it breaks down into other elements that whilst less radioactive (in an order of days to weeks lifespan instead of a LOT of years like uranium) it also gives off heat.

    Usually even this isn't a problem, the water still gets cycled, steam out cool water in and every things happy.
    With the reactor stopped power comes into the pumps from the local region.
    The local power got screwed by the quake though.
    Not a problem, the diesel backup generators kicked in and kept the coolant running... till the 23m wave broke past the 20m high tsunami defence wall and well... diesel generators don't much like breathing seawater and promptly decided to take their ball and head home pissed off.

    But AH HA! the batteries kicked in to cover the gennies spitting the dummy out the pram, I don't know if the electrics fried or if they operated normally till they ran out of juice, either way they didn't buy much time and the pumps stopped pumping, things got hot.

    HEAT, PRESSURE AND EXPLODY STUFF
    without the pumps to cool the system several things start to happen.
    1: things get hot and start to boil and melt.
    2: depending on the part depends on the seriousness.

    Control rods
    These melt at fairly low temperatures, when they melt they pool at the bottom of the beer keg and stop "controlling" the reaction. causing other parts to melt.
    the upshot is that whilst they gradually melt the reactor gets hotter and other parts begin to melt, this is good because if the fuel rods melt they prevent themselves from making a very big bang

    Fuel rods
    A couple of things happen with fuel rods when the fit hits the shan, none of them pleasant.
    Firstly if Zirconium gets exposed to steam it starts to produce Hydrogen. Hydrogen under heat and pressure likes to get all pissed off and explody.
    The uranium begins to dribble out and pool at the bottom of the reactor and get very hot, melting like magma through everything, the beer keg floor, the lead and concrete lining and eventually the top soil, rock all the way down, releasing radioactive shit as it parties on down, this can contaminate a wide area and cause all kinds of bad stuff.

    The beer keg pressure vessel.
    These are built for pressure, its in the bloody name, but like anything else it can only tolerate so much before it pops like a balloon.

    omfg wtf we do?
    The solution to it all is simple, cool shit down.
    The complication lays at the feet of the pumps being off-line, they cant get back on-line cause there's no juice, you cant get at the equipment because, well, theres radiation everywhere. radiation isnt friendly towards people and its spiking at rates where after a few hours people get all kinds of messed up.
    you wanna wander into an invisible nightmare with a toolbox be my guest.

    so the next option is to flood stuff with seawater.
    The decision to do so isn't as clear cut though, seawater is corrosive, ask any boat hull, its full of salt.
    Salty steam even more so, so whilst it cools things it might make them worse.
    Its also hard to contain, radioactive water sloshing around isnt ideal.
    neither is a rather large bang so screw it, they've started dumping in seawater with boron powder.

    This in turn boils and introduces more pressure int0 the system, the solution is to vent the pressure, this releases some of the secondary waste that's only slightly radioactive(the short lifespan shit) again not ideal but in this case necessary. the problem is whilst venting they vented hydrogen and gone and blown the roofs off the reactor huts. looks scary but surprisingly the 1960s reactors don't seem to troubled by the explosions, they're still by and large intact.

    It's also why people are freaking out, things going bang is scary as is the newspapers printing panic pieces like "Exposed Fuel Rods" this sounds nightmarish but as you've learned it doesn't mean out in the open, it just means not covered in water, theres nothing out in the open air, everything is still contained in the reactor vessels.

    so all that's left to do now is keep on dumping in water and hoping to hold out for a few says till stuff cools enough to, you know, not melt itself and cause worse things to happen.

    So yeah radiation is being vented, its only the less harmful stuff though, as opposed to letting things go and watching another Pripyat.
    People are dumping as much water as they can, venturing into places that are very inhospitable, you've got under an hour near the reactor at this point before you hit your yearly dosage of 50 miliSieverts or 5 REM.
    anything over an hour and your risking all kinds of bad things and long term problems.
    So all thats left now is to chopper in more water and hope the people holding conventional fire hoses dont wind up seriously mutated.
    He who laughs last thinks slowest.

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    What I can not understand why this nuclear reactors are built near the sea/ocean/river I would have thought the safest place would be on the mountains, we will have to learn from our mistake and for the Japes the game is over no more Japes products for some time to come.
    We should give them all the help they need and my condolences for the love ones.
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    because its hard to get water supplies in abundance up a mountain, next to the sea is ideal cause theres plenty of cold water near and you can use it to cool the reactors, even in the case of contained steam, running water over a contained radioactive source is ideal.

    Up a mountain there's no efficient way to cool the rods and things go bang as a result.
    He who laughs last thinks slowest.

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    well after reading that, you can't say the jap didn't try, nice to see an intelligent member of DK, or at least with GMB45's cut and paste skills don't under stand why they was unable to "turn it up a notch" and restart the dynamo to pump the water round?

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    Just to add a bit of info to that lovely description of a nuclear reactor.

    The core is flooded with water, but this is usually a sealed system. The super heated water (as it's under immense pressure it cannot turn to steam) is used to heat up another water system that does turn to steam that then powers the turbines.

    It's just like an old back boiler. Only instead of using gas to heat the sealed system, it uses uranium. This heated water then runs through the hot water tank heating up the water that comes out of the taps.

    It's this secondary water system that's being flooded with seawater, not the sealed system.
    Canker

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    There is something you're forgetting though and that is MOX.

    Reactor 3 is a MOX reactor.

    MOX (mixed oxide) is 2,000,000 times more lethal than the typical enriched uranium in the other reactors.A single milligram (mg) of MOX is as deadly as 2,000,000 mg of normal enriched uranium.

    MOX has twice the exposure rates of uranium and 4 times the affected area.

    When a uranium rod is spent it is then removed and disposed of as nuclear waste but the rods in a MOX fuelled reactor are removed and reused. The plutonium from used rods is mixed with new uranium then put into the reactor.
    All the used rods are stored in a containment area on a level above the reactor...the exact same level that exploded. Apparently the spent rod area in Reactor 4 is on fire as well and they are now reporting that the containment area for the MOX rods is fully exposed.

    Its a lot worse than just pumping water...





    Last edited by Cronus; 18th March, 2011 at 06:23 PM. Reason: spelling

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    Where's Bart Simpson when you need him?

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    So, would it be possable if Bart Simpson, or Beavis and Butthead could piss on it, would that help?

    secondly 'where' did the hygrogen gas come from?

    Does the plant still conform to the required Health and saftey at work act 1974?
    or COSH?

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    What a very informative thread, sure makes you realise the severity of the situation in japan.
    There are some very brave and conscientious employees at the nuclear plant prepared to continue trying to preserve the radioactive fall out to a minimum for as long as they can, surely they must be contaminated and know they are going to die and in true Japanese style they will try to protect the loss of public life at the expense of there own.
    May all those who were killed in this disaster Rest in Peace and my thoughts go out to the families who have lost loved ones.

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    Quote Originally Posted by SOB60 View Post
    What a very informative thread, sure makes you realise the severity of the situation in japan.

    , surely they must be contaminated and know they are going to die and in true Japanese style they will try to protect the loss of public life at the expense of there own.
    thought it was the Japanese that had kamikaze piolts (why did they wear helmets?)

    At lest the ones affected by the radiation will be able to light up the cemetry, as they will be glowing in the dark

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    Quote Originally Posted by Meat-Head View Post
    So, would it be possable if Bart Simpson, or Beavis and Butthead could piss on it, would that help?

    secondly 'where' did the hygrogen gas come from?

    Does the plant still conform to the required Health and saftey at work act 1974?
    or COSH?
    Hydrogen gas is released when Zirconium gets exposed to steam.
    Meaning the fuel rods are no longer submersed in water but superheated steam instead.
    Think of it like a boiling kettle without any water in it, it doesn't end well, only instead of the nasty fizzing sound and a tripped RCD/Breaker you get stuff melting and releasing hydrogen.

    On the bright side SOB60 the workers and aid know whats going on, unlike the situation in Pripyat with the Chernobyll reactor, where people where just slung in at the deep end with no real heads up to the risks.

    The storage area must be an inferno! MOX rods are way hotter than standard U/Zr rods, hot enough to turn steam into plasma
    Shit just got scarier.
    He who laughs last thinks slowest.

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    Quote Originally Posted by chroma View Post

    The storage area must be an inferno! MOX rods are way hotter than standard U/Zr rods, hot enough to turn steam into plasma
    Shit just got scarier.

    wicked, got a youtube link?

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    The US has already warned that the water in the fuel pool has gone.

    Here's a rough estimate of how much this facilty has

    ? Reactor No. 1: 50 tons of nuclear fuel
    ? Reactor No. 2: 81 tons
    ? Reactor No. 3: 88 tons
    ? Reactor No. 4: 135 tons
    ? Reactor No. 5: 142 tons
    ? Reactor No. 6: 151 tons
    ? Also, a separate ground-level fuel pool contains 1,097 tons of fuel; and some 70 tons of nuclear materials are kept on the grounds in dry storage.

    The reactor cores themselves contain less than 100 tons of fuel.

    Reactor 3 is the one with the MOX. Here's the size of a MOX pellet



    Imagine how many of these pellets there are to make up 88 tons!!

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    BOOM - SORRY- BUMP

    SO what's the story morning glory, is everything still going jack-a-norny?
    do we have to move to the country and eat a lot of peaches, peaches for free?





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    nobulk buy,too many people effected

 

 
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