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Regolith
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Saerynide is correct your talking more than 200 megawatts of residual core heating from decay of fusion products. Thats a huge pile of water, further
the failed cooling systems prevent cooling the core at the speed required.
Entropy, I know amazing isn't it? It's not certain but one of the running theories behind what threw the immensely heavy, 2000 ton, reactor cover off
the damaged reactor as it spiked to nearly 30GW. It's what happens when you build reactor cores so massive that a supercritical mass can be achieved
in the core. Chernobyl was 3200MWT it was just far too much fuel in one core. Fukushima is a mere 784MWE by comparison. Fukushimas number 1 reactor
is even smaller than 2 and 3 .
For those so interested there is an excellent documentary that can be had right online. There are more opinions found than just this about chernobyl
and this one doesn't go into the reasons behind why technicians who weren't correctly trained were operating the reactor at all. However it's a great
starting point.
http://topdocumentaryfilms.com/the-battle-of-chernobyl/
edit, dang spellcheck didn't have supercritical
[Edited on 15-3-2011 by Regolith]
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arsphenamine
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MIT handed the "What? Me, worry?" document over to its Nuclear Science and Engineering department for emendation.
It is much improved and worth the read.
http://mitnse.com/2011/03/13/why-i-am-not-worried-about-japa...
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Sedit
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Curious, is there no material they could fill the reactor with which the Uranium would melt and disperse in? Since its in the oxide form Im possitive
it would mix with glass and seriously lower the radioactive release. Materials like Borosilicate should not only mix in the molten state with the
oxide but also aid in neutron absorbing. In theory it could make handling the reactor and cooling it simpler. One of the ways they dispose of depleted
fuel is by mixing it into a glass anyway but I would be concerned if they would be able to mix the compound before the temperature went to high.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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madscientist
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I think they're more concerned about a decrease in surface area at this point. Anything that joins the rods together into a single mass will do this
and make it massively more difficult to cool.
I weep at the sight of flaming acetic anhydride.
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gregxy
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Its interesting to do some math:
The power for the 3 reactors was 1800Mw before the quake.
The residual power should now be <5% of that or about 100Mw
(I saw a nice graph on one website showing how the power
declines over time but I lost the link)
The heat capacity of water is ~4 kJ/kg/K if the water goes in
at 30C and comes out at 80C then each kg can carry 200kJ
So the flow rate is 500kg/sec or about 125 gallons/sec
A typical fire hydrant can put out 25 gal/sec so you will need
5 of them. Not a huge amount of water for a few big
diesel pumps.
The water mains were probably damaged and there is
no way to truck in this much water, which is why they
are using sea water. If the core is damaged radioactive
material will disolve into the water. The claim to filter the
water but how? The water probably goes out
the cooling outlet for the plant, probably far out to sea.
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Magpie
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Interesting calculation gregxy. Your calculation assumes that the water is in the vessel long enough to get heated a delta of 50C. This is where the
available surface area for cooling becomes very important.
[Edited on 15-3-2011 by Magpie]
[Edited on 15-3-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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ScienceHideout
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Telling the truth, I watched a TV show explaining everything. Doesn't sound too bad.
You may have heard, "The rods are exposed!" That simply means that the uranium supply is no longer underwater. No big deal.
The phrase Meltdown refers to when the uranium rods melt the outer shell.
And the explosions- just the engineers releasing pressure.
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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gregxy
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How hot the water gets depends on the flow rate. Reduce
the flow rate and the delta T becomes larger resulting
in more removed heat per kg of water. Of course the flow
rate must be high enough to ensure even cooling.
And if the water becomes hot enough to boil the back
pressure could prevent pumping water in. I'm sure they
planned for all this using the regular back-up.
If the core goes dry it is a big problem. I suspect it only takes
minutes to reach the melting point for the zicronium tubes.
(If you know the mass of the core you can figure it all out).
And if the core becomes hot enough to deform water flow
will become non-uniform resulting in hot spots and more
heating etc.
But the "worst should be past" since the heat output
declines with each day.
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madscientist
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ScienceHideout: when fuel rods are exposed, they begin to melt. When they are completely molten, it's a meltdown.
Does <a href="http://www.youtube.com/watch?v=T_N-wNFSGyQ">this</a> seriously look like deliberate venting of steam? If that's what it is,
I won't be buying any pressure cookers from Japan! 
I weep at the sight of flaming acetic anhydride.
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entropy51
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Quote: Originally posted by ScienceHideout  | Telling the truth, I watched a TV show explaining everything. Doesn't sound too bad.
You may have heard, "The rods are exposed!" That simply means that the uranium supply is no longer underwater. No big deal.
The phrase Meltdown refers to when the uranium rods melt the outer shell.
And the explosions- just the engineers releasing pressure.
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As madscientist said, fuel rods not cooled by water are heating up. The rods continue to generate energy
due to decay of radioactive fission products. If it is not removed by flowing water, where does it go? Nowhere. It heats the rods up until the
zirconium cladding begins to react exothermically with the steam and generate hydrogen and more energy, which further raises the temperature. You
need to watch better television, or God forbid, read a science book.
gregxy, your 1800 MW figure is the electrical output of the plant. The thermal power is about three times as much.
I love this thread. It is a classic example of how intellectual arrogance finds itself in company with ignorance.
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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gregxy
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I made a mistake in my earlier post, The decay heat at
this point should be < 0.5% of the original reactor power
so only 10Mw of power needs to be removed (for all 3 reactors)
Or about 12 gallons/sec of water, which can be supplied by
one 3" fire hose.
http://en.wikipedia.org/wiki/Decay_heat
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Sedit
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Just to play devils advocate here for a second I want to remind everyone that all our assumptions are based on the fact that they are telling the
truth about the control rods being in place. Mind you nothing they have said so far has been true and its all be a PR campain, that I don't disagree
with really, to keep the general public from going into all out crisis mode. They got enough on there plate to be worried about sudden death.
I would think logic would dictate that the secondary chain reactions would be weaker then the primary one. However even with the control rods in place
everyones saying the heat is comming from the secondary reactions. I doubt this as it sounds unreasonable. If the control rods can stop primary
fission why can't they control the neutrons from a weaker secondary reaction? With the control rods in place the neutrons causing the heat should be
absorbed into the control rod and primary and secondary should cease and prevent the chain reaction from taking place all together.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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entropy51
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| Quote: Originally posted by Sedit | | With the control rods in place the neutrons causing the heat should be absorbed into the control rod and primary and secondary should cease and
prevent the chain reaction from taking place all together. |
What is this "secondary chain reaction"? If you
mean the decay heat, that is due to the radioactive decay of the fission products that were formed while the reactor was in operation. There are no
neutron reactions involved at this point. Once the fission products were formed (before the shutdown on Friday), they will decay according to their
half-lives and nothing can slow that down, speed that up, or stop it. The energy of the decay just has to be removed or it will heat up the fuel.
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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entropy51
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So greg, do you think those poor guys who are down there at Fukushima Daiichi tonight, getting their
innards cooked, trying to save that plant and a lot of lives, didn't think of your simple solution?
I guess those nuclear engineers aren't smart enough to just stick a fire hose in it, call it a day, and go home.
Or. according to your calculation, why don't they all piss on it at the same time? That would provide the flow rate you calculated, wouldn't it?
Oh wait! You don't suppose you could be missing some subtle nuance of heat transfer or thermodynamics or hydraulics?
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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Sedit
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| Quote: Originally posted by entropy51 | | Quote: Originally posted by Sedit | | With the control rods in place the neutrons causing the heat should be absorbed into the control rod and primary and secondary should cease and
prevent the chain reaction from taking place all together. |
What is this "secondary chain reaction"? If you
mean the decay heat, that is due to the radioactive decay of the fission products that were formed while the reactor was in operation. There are no
neutron reactions involved at this point. Once the fission products were formed (before the shutdown on Friday), they will decay according to their
half-lives and nothing can slow that down, speed that up, or stop it. The energy of the decay just has to be removed or it will heat up the fuel.
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No not the latent heat, the supposed breakdown of the formed radioactive compounds. Everyone has been focused on the heat produced not from the
primary fission of the Uranium but the fission of the biproducts. I don't feel they would be sufficient to heat the reactor to over 3000 degrees C in
45 minutes with the control rods in place as everyone is suggesting.
[edit]
Ehchem.... 3" firehose.... pissing, your sure are an optimist aint ya Entropy
[Edited on 16-3-2011 by Sedit]
edit2
Once again im on point, don't hate me for it I just can't help myself.
http://www.aolnews.com/2011/03/15/japan-nuclear-reactor-stor...
Basicly,,, there fucked to put it bluntly. They have 4 reactors in the same complex all over heating. They are left with nothing but firehoses at this
point to put out a fire... partial meltdowns have happened in them and its a waiting game now.
Its over! Whatever can happen will happen, They are wasting there time fighting it and should evacuate everyone and watch from a safe distance as
there poor planning comes to light.
At what point do you toss in the white flag and run for your mother fucking lifes?
[Edited on 16-3-2011 by Sedit]
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Elawr
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I agree... the garbling of technical details by the press media reflects the appalling loss of general scientific knowledge suffered by our
society...So, this is the reason I can watch TV news no longer than 5 or 10 minutes before my eyes began to fog over and I start drooling! To me, it's
as scary as the idea of nuke meltdown fallout raining down on my head.
I turn to Sciencemadness.org for the salient facts.
So, I am I correct in understanding that , although at least 4 separate nuclear power facilities have been compromised by Japan earthquake, only one
of these is actually impending meltdown albeit in 3 of 4 of its reactors?
Some older reactor designs depend upon the neutron-slowing effect of cooling water to help control fission reaction, thereby inherently unstable in
event of coolant loss. Surely this is not the case here... are not modern reactors safer in this regard? (or is it other way around...)
I see your point Sedit, if the radioactive decay products (embers, as it were of the fuel consumed) release such tremendous energy,....then.. uh
Truth is, I think, no one quite knows for sure. Quite a complex mix of unstable nuclides of all different half-lives making up that unimaginable hell
cauldron bubbling at the bottom of those reactors. I sure as hell would not want to study it!
Think I'll just go watch a favorite "Outer Limits" episode I once taped: "The Production and Decay of Strange Particles".
Now might be a good time to put your surplus KI up for sale on eBay...:-)
[Edited on 16-3-2011 by Elawr]
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Regolith
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Elawr, your mostly correct. There are several nuclear sites in japan (they get more than 30% of their energy from nuclear), most of them achieved cold
shutdowns following the quake, albeit several are scrambling to make sure they have diesel fuel for cooling. In many cases there pumping out water
from access points (flooded from the tsunami) they need to get into to attach power lines from generators.
At the Fukushima plant they have 6 reactors, at this point reactors 1, 2 and 3 are in meltdown. Meaning that even a small part of the core (70 percent
of one core apparently ) has been exposed and has melted. This is the end of a
reactor, even before they sprayed in seawater to cool the reactors (seawater contamination requires decommissioning this type of reactors on its own).
Reactor 4 seems to be stable but the cooling pond that houses the fuel used in the last loading has boiled dry and has broken out in flames. It
doesn't mean the end of the world however. These units were built with this (failsafe) in mind and every day that passes means another day of shutdown
and the latent fission products are decaying more and more and cooling down.
The type of reactor where the water leaving the core causing a power rise is what happened in chernobyl. Modern designs try to have the opposite or
have a core that is designed to run at maximum temperature without a human intervening. Pebble bed reactors are one such reactor. As mentioned above
with a PBR you really can just run for your life and ignore it until you have the systems ready to bring it back under human control. On the other
side of the scale is what you mention, which is basically a raw nuclear pile, chernobyl, in its primitive design, it lacked only the people standing
above it with buckets of water reminiscent of the chicago pile.
All this said, they have detected a crack in one of the calandria(reactor vessels) at fukushima I and that IS very bad if the crack extends all the
way inside. Scientists here will be well aware of low viscosity molten products that can flow just like water and need only the tiniest space to get
out. Provided they can prevent the core melting completely this can still be dealt with.
I read the article sedit posted above and this sticks out to me as shoddy journalism.
"A U.S. nuclear expert said he feared the worst. "It's more of a surrender," said David Lochbaum, a nuclear engineer who now heads the nuclear safety
program for the Union of Concerned Scientists, an activist group. "It's not like you wait 10 days and the radiation goes away. In
that 10 days things are going to get worse."
Yes it is like you wait 10 days. (further he's an activist group, HELLO ? AOLnews you guys ask questions? or just nod and smile ?)
The longer you get from the time the core was online the cooler it's going to become. The isotopes created in the reactor often have short half lives
a month is often required to get to a full shutdown. At a certain point it wont boil water anymore. This isn't the world ending disaster people are
blowing it into its being driven by a hatred for nuclear power at many news organizations. If they can keep containment on the reactor in any form, it
will be removable by barge to a proper disposal site which is what was slated anyway in a few years.
I'm an advocate FOR nuclear power. Even after this, with the building collapsing and the workers now abandoning the site due to radiation, fyi, it's
likely the crack in the reactor DOES go all the way through. Japan is a tiny island what other way do they have for power generation? Personally I
think we should be using discreet nuclear reactors like those of the toshiba lithium moderated or the smaller designs from adams atomics, which has
designs small enough to replace diesel sets in large watercraft and buildings.
A chernobyl this will not become a month from now this won't be in the news anymore as obama pushes for his next election or the next major disaster
comes up. Everyone on earth during chernobyl was able to step outside and detect the increase in background radiation from that accident. The
difference in scale of this disaster is enormous.
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bfesser
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Has anyone else noticed the sudden increase of listings for potassium iodide on eBay since these events? Some of it's listed for absolutely <a
href="http://cgi.ebay.com/Potassium-Iodide-/260753097989">ludicrous prices</a>!
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Chordate
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Even scarier are the people bidding 50 dollars on a bottle of iodine/potassium iodide solutions.
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hissingnoise
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The serious problems Japan now faces are the result of human error!
The worst-case-scenario just wasn't planned for . . .
The generators should have been built to be impervious to all tsunami!
Lessons will, we hope, be learned from this catastrophe but it's coming at enormous cost to a people already pretty devastated.
The entire thing is beyond words, essentially . . .
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Magpie
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Many years ago when I worked in nuclear waste management we somehow ran across a flyer for KI pills. It had a picture of the grim reaper and
something about "this is not the government's 'get-out-of-town pill.'"
What I can't understand is why they were not successful at flying in diesel generators. With sufficient pumping capacity it seems that they could
have had safe and normal shutdowns, and kept their spent fuel pools cool. I wonder if we are not being told the whole story here.
-----------------------------------
Use of normal cooling water (deionized, I would think) would also depend on the piping and heat exchangers that exchange heat with seawater retaining
integrity. After an 8.9 earthquake this may well not be the case. These are just my speculations, I've heard no such reports from the Japanese.
[Edited on 16-3-2011 by Magpie]
[Edited on 16-3-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Saerynide
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I think they need to extend the evac radius because when things get bad, there won't be time to get everyone out, and everyone trying to run will make
it even harder for them to get out. Hell I wouldn't want to be 12 miles away when a reactor (or all 4) goes critical - you'd be able to see it out
your window!
I really hope they are collecting the concrete necessary and keeping it close on standby, along with remote control dump trucks to pour it so that
when it comes time to abandon ship and run for their lives, the remote control equipment can get started right away pouring cement.
Lava shouldn't be coming out the bottom before they decide they need it...
"Microsoft reserves the right at all times to monitor communications on the Service and disclose any information Microsoft deems necessary to...
satisfy any applicable law, regulation or legal process"
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gregxy
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| Quote: Originally posted by entropy51 | So greg, do you think those poor guys who are down there at Fukushima Daiichi tonight, getting their
innards cooked, trying to save that plant and a lot of lives, didn't think of your simple solution?
I guess those nuclear engineers aren't smart enough to just stick a fire hose in it, call it a day, and go home.
Or. according to your calculation, why don't they all piss on it at the same time? That would provide the flow rate you calculated, wouldn't it?
Oh wait! You don't suppose you could be missing some subtle nuance of heat transfer or thermodynamics or hydraulics? |
Of course it is harder than connecting a fire hose to the reactor. And the people that designed the thing know all this to 5 decimil places. I'm just
trying to get some understanding
of the magnitude of the problem since you cannot tell anything from the media reports. Even if I'm off by 10X it
is still managable situation. If you don't agree with it
fine. Present a better calculation, anyone can throw stones.
They have made it through the most critical phase which
was the first 24 hours after shut down. In about 5 days
the media and everyone else will tire of the whole thing.
It will be a huge mess to clean up but its unlikely there will
be a single death due to radiation.
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Sedit
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I want to agree but given the fact that the news crews covering the story from some distance away have just tested positive for radiation even after a
scrub down means there may be more then they are letting on to. They didn't say what strength the reading they got on him just that it was showing up.
I guess all there is to do is wait a couple weeks and see. If its still a big problem then, then they are lying about the control rods being in place
which may be a real possibility since you had an extremely powerful earthquake followed with a huge wave. Its obvious they are patting there people on
the head and telling them its alright but there is a huge question as to how bad the situation really is. There word is worth nothing and honestly
little of there facts are.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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ScienceHideout
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| Quote: Originally posted by madscientist | ScienceHideout: when fuel rods are exposed, they begin to melt. When they are completely molten, it's a meltdown.
Does <a href="http://www.youtube.com/watch?v=T_N-wNFSGyQ">this</a> seriously look like deliberate venting of steam? If that's what it is,
I won't be buying any pressure cookers from Japan! |
Notice the "explosion" came from here. To me, those look like functional cooling towers.
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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