In Meltdown News: "It won't come out as one big glob; it'll come out like lava, and that is good.."

[flamingdem]

http://www.guardian.co.uk/world/2011/mar/29/japan-lost-race-save-nuclear-reactor

I think this article is updated from this morning?

Richard Lahey, who was head of safety research for boiling-water reactors at General Electric when the company installed the units at Fukushima, told the Guardian workers at the site appeared to have "lost the race" to save the reactor, but said there was no danger of a Chernobyl-style catastrophe.

--- snip

The major concern when molten fuel breaches a containment vessel is that it reacts with the concrete floor of the drywell underneath, releasing radioactive gases into the surrounding area. At Fukushima, the drywell has been flooded with seawater, which will cool any molten fuel that escapes from the reactor and reduce the amount of radioactive gas released.

Lahey said: "It won't come out as one big glob; it'll come out like lava, and that is good because it's easier to cool." (Relatively upbeat news here!)

The drywell is surrounded by a secondary steel-and-concrete structure designed to keep radioactive material from escaping into the environment. But an earlier hydrogen explosion at the reactor may have damaged this.

--snip

[Buzz Clik]

1. Hm. I guess that's as good as the news is going to get.

[enlightenment]

2. How does he know it will 'come out like lava' as opposed to

'one big glob'?

Did they do real tests on the vessels, using real fuel rods - or did they do computer simulations?

I hope what he is saying is true, I really do, but it's hard to accept at face value the comments of someone who designed a system that has been criticized by experts for almost as long as it has existed.

http://readersupportednews.org/news-section2/338-177/5291-reactor-design-in-japan-has-long-been-questioned

[FBaggins]

3. I think what he's explaining is why a re-criticality event was so unlikely.

People seem to think that the core just melts all together into a great big lump and then the whole thing burns through everything in its path. That was close to true in Chernobyl, but that's because the reactor was not only active, but powered up during the accident (to WELL above full power).

In Fukushima, that wouldn't have been the case. Water levels declined within the core, which could have allowed uncovered portions of the fuel assemblies to melt. But anything that melted would then fall to where the water level was (say, half way down the fuel) and re-solidify. If (as appears to be the case in at least one reactor) the fuel rods were entirely uncovered, you could get melting from anywhere in the core, but it would again happen in segments. Since there was still water in the RPV (just below the level of the bottom of the fuel), it would again re-solidify as it hit the water and would sink to the bottom of the RPV not in a single mass, but in chunks. The same thing could happen if some molten core made it through the RPV. The drywell was also flooded with water, so it wouldn't get to the bottom of the drywell as molten material, but as pieces.

One great big "blob" of corium (as we speculate occurred at Chernobyl) wouldn't solidify quickly enough... it also wouldn't have much opportunity for other materials to mix in that might poison the reaction.

Of course this doesn't mean that any of this (apart from the primary core damage) happened... it's just his speculation.

[flamingdem]

4. What about this scenario:

Only flaw in this argument is that once it tunnels through primary containment vessel, it allows a further reduction in the water level which is what is covering the remaining part of the fuel rods - remember they say this is a partial meltdown. Considering that the secondary containment has confirmed cracks, this will allow more water to escape. Now they can continue to try and fill the containment with more water, but that water will hit the uranium slag as it leaks out. As water hits the slag, it will release larger amounts of hydrogen which can (if not vented vigorously) cause another explosion. zerohedge.com

also:
That's what I said a few days ago, and the reason why they are desperate to pump the water out of the basement (reference "The Battle of Chernobyl"http://www.youtube.com/watch?v=yiCXb1Nhd1o )

This was the "Only" thing that saved Chernobyl from being a catastrophic world event. I know they keep saying thats it's in the turbine buildings, but I don't believe a word of it. The water is under the reactors. !

[girl gone mad]

5. Probably not best to..

try and reason with people who think that radioactivity is not a nuclear reaction, fission is not occurring in the presence of large masses of heavy isotopic elements, melting fuel isn't adding any heat to the system, etc. He can't google fast enough to make up for his lack of basic understanding.

[FBaggins]

7. Lol... you again?

Can't stick to the facts, eh? Need to make up your own strawman, eh?

radioactivity is not a nuclear reaction

It isn't (it's the result of one), but nobody said that. What I said was that nuclear decay isn't a nuclear reaction. When I was in school it wasn't... the atom has to react with something for it to be a "reaction"... but I do see that some references lump it all together so I stopped giving you a hard time about it.

fission is not occurring in the presence of large masses of heavy isotopic elements

No fission that is at all relevant to the discussion. Nothing that makes a rounding error in the fifth decimal place of a percent. But you were immune to correction.

melting fuel isn't adding any heat to the system

Now where did I say that?

Do we really need to go down the list of your ridiculous errors on those threads?

Really? Confusing heat and temperature? Thinking that Spontaneous fission is responsible for the heat in the reactor cores? That temperature has an impact on the rate of SF? The rate of fission and the temperature are correlated? That a reactor at one percent of therman output would be just a smidge above the freezing point of water? You can't get a meltdown without fission? When uranium melts, you get increased fission? Chernobyl never got back to critical? Need I go on?

Surely you're not that much of a glutton for punishment?

[girl gone mad]

9. At least you've stopped pretending...

that the fuel is just sitting in perfect configuration, merely putting off decay heat at 1% of normal output.

Maybe some day someone will write "Neutron Flux and Rates of Fission for Dummies".

The atom is "reacting" when it decays. When did you go to school, 1905? It's called quantum tunneling. Hurry up and google it.

[FBaggins]

11. There's no need to pretend.

merely putting off decay heat at 1% of normal output.

It was at 1% shortly after shutdown.

It's much LESS than that now. And yes, ALL of the heat (to several decimal places) is from DECAY... not FISSION.

Maybe some day someone will write "Neutron Flux and Rates of Fission for Dummies".

I gave you the rate of fission. You couldn't seem to grasp the significance.

[girl gone mad]

12. You don't know the rate of fission..

because you don't know precisely how the fuel is currently configured.

If we are talking about gobs of melted nuclear fuel flowing together into increasing masses of fissionable material, the rate of reactions (fission) will vary throughout, and some of these globs can become critical. Not sure why this is such a difficult concept for you to grasp.

[FBaggins]

13. Lol! You can add that one to the list.

Configuration is entirely irrelevant when it comes to spontaneous fission.

[girl gone mad]

15. Spontaneous fission can lead to induced fission..

as the fuel melts out of critical configuration and into uncontrolled configurations.

Why can't you get this?

The neutrons that are emitted during spontaneous fission are just like the neutrons that are absorbed and emitted during induced fission. They aren't special neutrons. They can cause chain reactions, too.

[FBaggins]

16. So now we're at "can"???

Something that you wanted to claim was a prominent source of the heat in these cores and now you want to say that it "can" happen? Care to speculate on the chances?

as the fuel melts out of critical configuration and into uncontrolled configurations.

Let's see if I've got this straight. A couple days ago you were sure that you can't get a meltdown without fission... now you're telling me that it's possible to get induced fission after the meltdown?

Tell me I'm not the only one who finds this hilarious?

The neutrons that are emitted during spontaneous fission are just like the neutrons that are absorbed and emitted during induced fission. They aren't special neutrons.

Really? "Just like"? Never heard of the difference between "fast" and "thermal" neutrons, eh? Better look it up. One is far less likely to induce fission.

[girl gone mad]

20. Materials within the melted fuel will..

moderate the neutrons, as will the water in the reactor (almost any liquid or solid moderates neutrons), and you "can" get chain reactions and criticalities.

Can you find an example of a meltdown event where rates of fission decreased or stayed constant throughout (at zero, as you claim)? I've never heard of this.

Yes, you are probably the only one who finds the idea of a nuclear meltdown "hilarious".

[FBaggins]

22. Sure I can give you an example

Can you find an example of a meltdown event where rates of fission decreased or stayed constant (at zero, as you claim)? I've never heard of this.

Basically every modern meltdown except Chernobyl (which melted down while active). Three-mile-island, Units 1,2,&3 at Fukushima, Lucens, Switzeralnd in the 60s, Bohunice, Czechoslovakia in the 70s. etc.

What you're missing is that it's close to physically impossible for fission to restart in this type of situation. The "configuration" that you keep refering to actually works against it. It's designed so that if elements fall OUT of the original configuration, the neutron economy breaks down. If control rods don't get inserted, but the water drains out... the neutron economy breaks down... if the whole thing melts down into a lump, the other elements in the mix (boronated steel etc), act against the neutron economy. Obviously in this case they've added massive amounts of new boron to the mix and that, too, acts to clog things up.

A re-criticality incident remains theoretically possible, but almost physically impossible.

And that's the only way that fission makes up more than o.ooooo1% of the heat in the core a couple minutes after shutdown.

Yes, you are probably the only one who finds the idea of a nuclear meltdown near "hilarious".

What's hilarious is your wild attempt at spin. You previously claimed that it isn't possible to have a meltdown without active fission. This was obviously because you didn't understand that the VAST bulk (99.999+%) of the heat in a shut-down reactor is from decay... not from fission.

Now you think you can rescue the original errors by proving that it's possible for active fission to re-start after shutdown. What's hillarious is that you think it's possible to save face even if you could prove that. Your first error was that the reactors MUST be running at more than 1% of power because if they were at that level, they would be at three degrees.

Have you gotten to the point that you understand how badly wrong that was?

Your next (larger) error was in thinking that most of the heat in these reactors came from fission. The notion that there's a one-in-ten-million chance that fission COULD restart, really doesn't demonstrate that fission is the source of the heat.

Have you gotten to the point that you understand how badly wrong that was?

[girl gone mad]

24. Post the links to back up your claims.

Here, for example, is a study which simulated meltdowns in boiling water reactors. The authors concluded that pockets of recriticality would occur, causing power excursions and power generation at a levels significantly higher than the decay power:

ftp://ftp.cordis.europa.eu/pub/fp5-euratom/docs/09-sara.pdf

You clearly do not understand physics, not even at the level of a first year undergraduate, so what is the point in trying to carry on a conversation with you?

Show me papers from real physicists purporting that fission remained at zero or decreased over the mass of the fuel during meltdowns at "Three-mile-island, Units 1,2,&3 at Fukushima, Lucens, Switzeralnd in the 60s, Bohunice, Czechoslovakia in the 70s. etc." I'm not about to take your word for it.

[FBaggins]

25. I can give you links till your ears bleed.

But we both know that you're immune to facts. By all means though, let's try again.

Here, for example, is a study which simulated meltdowns in boiling water reactors.

And did you by any chance read it? Understand what it says? Does the current situation (with, say, relation to boron in the water) match the hypothetical scenario? You don't even know how to tell, do you?

Let's assume that you were right for just a moment. Look at what you're left trying to prove. EVERYTHING in that article that relates to re-criticality assumes that the core has already heated up and the fuel elements have melted. You can't pretend that this hypothetical fission is responsible for the heat in the reactor if you need the heat AND meltdown FIRST before the hypothetical fission could occur.

You clearly do not understand physics, not even at the level of a first year undergraduate, so what is the point in trying to carry on a conversation with you?

I just love that M.O. of yours. Hoping and praying that bluster can get you through this. But you're like a moth to a flame... you just can't resist.

Show me papers from real physicists

You got it. Let's begin.

http://www.hss.doe.gov/nuclearsafety/ns/techstds/standard/hdbk1019/h1019v1.pdf#page=85.5">Nuclear Physics and Reactor Theory

Page 62 is the one relevant to our discussion.

When a reactor is shut down, fissions essentially cease, but energy is still being released from the decay of fission products. The heat produced by this decay energy is referred to as "decay heat." Although decay energy represents about seven percent of reactor heat production during reactor operation, once the reactor is shut down the decay heat production drops off quickly to a small fraction of its value while operating. The decay heat produced is significant, however, and systems must be provided to keep the reactor cool even after shutdown.

A "small fraction" of the original 7% you say? Doesn't sound good for you... but I know you're try and twist it. So let's quantify what a "small fraction" is, shall we?

Now... this one's a little beyond first year undergrad physics... but try to follow along. I'll point out the important bits.

http://www.scribd.com/doc/24000397/Fundamentals-of-Nuclear-Reactor-Physics-2008">Fundamentals of Nuclear Reactor Physics

Let's turn to pages 15 & 16.

Roughly 8% of the 200 MeV of energy produced from fission is attributable to the beta decay of fission products and the gamma rays associated with it. Thus even following shutdown of a chain reaction, radioactive decay will continue to produce significant amounts of heat. Figure 1.6 shows the decay heat for a reactor that has operated at a powerP for a long time. The heat is approximated by the Wigner- Way formula (see formula) As a result of decay heat, cooling must be provided to prevent over- heating of reactor fuel for a substantial period of time following power plant shutdown.

Notice the chart on Page 16? Look familiar? We are now more than two weeks post-shutdown. What percentage of decay heat remains? What was it after ONE day?

Note why they key was to get past those first critical hours?

Here's another:

http://www.world-nuclear.org/education/phys.htm">Physics of Uranium and Nuclear Energy

About 6% of the heat generated in the reactor core originates from radioactive decay of fission products and transuranic elements formed by neutron capture, mostly the former. This must be allowed for when the reactor is shut down, since heat generation continues after fission stops. It is this decay which makes used fuel initially generate heat and hence need cooling.

Here's a http://books.google.com/books?id=gAoAAAAAMBAJ&pg=PA63&dq=%22decay+heat%22+%22three+mile+island%22&hl=en&ei=AL-TTYbIELKF0QGL8NjkCw&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDMQ6AEwAg">Bulletin of Atomic Scientists piece from not long after TMI, explaining some of what you misunderstood.



Here's a link to http://www.world-nuclear.org/education/phys.htm">Three Mile Island: A Nuclear Crisis in Historical Perspective. It should take you to page 53 (which is clear enough on your error), but you'll also want to look at pages 54 and 73.

The control rods entered the core and terminated the production of heat from nuclear fission. But the problem of dealing with decay heat remained.

The word you're looking for here is "uncle". :)

[girl gone mad]

26. Let's just recap the things that you've gotten wrong so far.

You adamantly insisted that all fission had ceased inside the reactors at Fukushima.

Once you learned about spontaneous fission, you insisted that it's not a "nuclear reaction".

You made a big point of differentiating between heat and temperature, as if the rising temperatures had some external cause.

You stated that the configuration of the fuel is an irrelevant factor in determining the rate of fission.

You stated that neutrons from spontaneous fission won't be thermalized, thus can't cause significant induced fission.

You still insist on pretending that the reactors magically followed a decay heat loss probability chart for a normally shut down reactor, despite total loss of power and cooling, partial meltdowns and other loss of control events.

You don't know how to read and interpret a scientific study that says very plainly that after total power and cooling loss at a boiling water reactor, pockets of fission can become re-critical and steady-state power levels can rise significantly.

You deny that chain reactions can be occurring, despite the fact that the http://www.bloomberg.com/news/2011-03-30/record-high-levels-of-radiation-found-in-sea-near-crippled-nuclear-reactor.html">IAEA said today that they are.

None of the links you provided can support your assertion that the rate of fission decreased or remained at zero during a reactor core meltdown.

I don't understand why someone who has been demonstrably wrong so many times would continue down a path of buffoonish arrogance, insisting that he possesses a level of expertise which he so clearly does not.

[FBaggins]

27. By all means... let's.

You adamantly insisted that all fission had ceased inside the reactors at Fukushima.

Yep. And that's because I'm perfectly willing to round 0.000000000001% to "zero". That seemed too much for you. And that's not a made up number... it's the actual percentage of power in an active reactor from SF. Once the chain reaction shuts down and delayed fission ends and reactor power drops to 1% of what it was originally (say... after a couple hours) the heat contributed by SF leaps (relatively) all the way up to .0000000001% of power.

I'm still willing to call that "zero". If you want to speculate that SOME of those SF events induce fission once in awhile and "score" that heat as related.... we can pretend that it's ten or even one hundred times as much... and you're still left with .00000001%

Still rounds to "nada". I get a kick out of how you start with a position that says that MOST of the heat comes from fission and I (correctly) tell you that it really doesn't account for anything... and you seem to think that you can "win" the argument by proving anything above dead zero counts as you being right. :rofl:


Once you learned about spontaneous fission, you insisted that it's not a "nuclear reaction".

Learned about SF? Give me a break. It's you that's been learning about SF... and you're still not done it seems. But yes, ONE point for you. I always assumed that a nuclear reaction had to actually involve a nucleus reacting with something. Wow... 25 errors on your part and you caught me on one that was irrelevant. You must be so proud.

You made a big point of differentiating between heat and temperature, as if the rising temperatures had some external cause.

"external" in this case meaning "something other than what YOU said was causing it"? Then yes... I was 100% correct.

Differentiating between heat and temperature was the primary depth of your original ignorance. I know that you think you dodge the point by insisting that .0000000001 is not EXACTLY zero, but your original error was claiming that the reactor cores can't be at 1% of power because if they were they would be at three degrees. Have you figured out how desperately wrong your original positon was?

You stated that the configuration of the fuel is an irrelevant factor in determining the rate of fission.

Wrong. I said it had nothing at all to do with the rate of spontaneous fission. And it doesn't.

You stated that neutrons from spontaneous fission won't be thermalized, thus can't cause significant induced fission

I never said that they can't be "thermalized"... but I did say that they don't cause significant fission. And they don't.

You still insist on pretending that the reactors magically followed a decay heat loss probability chart for a normally shut down reactor, despite total loss of power and cooling, partial meltdowns and other loss of control events.

Wow... right back to your original errors, eh? You haven't learned a thing? You didn't believe that the graph was legit and now you're doubting it even though I literally gave it to you from a textbook on reactor physics? A few points for you to learn:

1) Loss of power does not change the rate of decay. Half lives are constants.
2) Meltdowns do not change the rate of decay. Half lives are constants.
3) Decay is not a matter for human "control"... so loss of control doesn't change decay rates. Half lives are constants.

You deny that chain reactions can be occurring, despite the fact that the IAEA said today that they are.

Is that what they said? That's funny... the story must have been changes since you read it. Now it says "The IAEA acknowledged "they don’t have clear signs that show such a phenomenon is happening," Edano said. "

None of the links you provided can support your assertion that the rate of fission decreased or remained at zero during a reactor core meltdown.

Wow... did you read them at all?

"When a reactor is shut down, fissions essentially cease, but energy is still being released from the decay of fission products"

[girl gone mad]

28. If I were you, I would be too embarrassed to keep kicking this thread.

Not only have you been shown to be wrong theoretically, but now you have also been proven wrong empirically.

You are left to try and parse your way out of a disastrous display of ignorance, furiously clinging to the little talking point bulletin you were given weeks ago. But you don't have enough scientific training to even make a sensible display of it. Give it up already.

[FBaggins]

29. Of course you wouldn't be...

...since that's exactly what you've been doing. :rofl:

You are left to try and parse your way out of a disastrous display of ignorance

How ironic. Have you READ your prior posts? Or do you have the ability to block them from your memory entirely?

Has there been ANY of your original points that held water even as well as one of these reactors?

Nope... not a one.

[PamW]

30. Girl gone mad is WRONG!!!

Sorry to have to tell you this - but you are the one that is flat out wrong

Even nuclear reactions give off extremely little macroscopic energy. The only way
you get large amounts of energy is if the chain reactions are self-sustaining.

This is where you totally missed the point with the IAEA link you posted - those
"flashes" are not self-sustaining and hence are not really a problem. You really
should refrain from attempting to discuss and cite science you evidently don't understand at all

PamW

[FBaggins]

32. In other (equally shocking) news...

... the sun sets in the west again!

:)

[girl gone mad]

36. Damn. I wish everyone who unabashedly supported nuclear energy..

could read this thread and read the things you are saying and understand that even people who work in the industry are often totally clueless.

This is something I have seen many times in person, but here is more evidence.

[PamW]

53. There you go again...

could read this thread and read the things you are saying and understand that even people who work in the industry are often totally clueless.
===================================

There you go again, assuming facts not in evidence.

Where did you get the idea that I work in the nuclear industy?

For you information, I do not work in the nuclear industry.

Are your thought processes always this chaotic and disordered?

You make up your own definitions of words...
You make up your own facts with no justification....

If you were planning a career in science, you better forget it.

Stick to political "science".

PamW

[FBaggins]

54. You mean like the Union of Concerned Scientists?

http://www.ucsusa.org/nuclear_power/nuclear_power_risk/safety/nuclear-reactor-crisis-faq.html#reactors%20are%20shut%20down

Q - If the reactors are shut down, why is cooling a problem?

A - When the reactor shuts down, the fission process in the nuclear fuel stops. However, the fuel is very hot, and is still highly radioactive. When the radioactive particles decay, this produces additional heat.

[PamW]

55. The UCS is a union of anything [b]BUT[/b] scientists...

When the radioactive particles decay, this produces additional heat.
===========================

They must be referring to the neutrons with their 15 minute half-life.

Definitely NOT scientists in the UCS.

PamW

[Name removed]

42. Deleted message

Message removed by moderator. Click here to review the message board rules.

[PamW]

31. Girl gone mad is WRONG!!! again

The neutrons that are emitted during spontaneous fission are just like the neutrons that are
absorbed and emitted during induced fission. They aren't special neutrons. They can cause chain reactions, too.
==================================

Boy you REALLY don't know your neutron physics. A neutron is a neutron is a neutron.

However, the spectrum of spontaneous fission and the "nu" factor are different than
induced fissions.

It's like saying a car is a car is a car. But a car going 45 mph is not the same
as a car at rest.

Why do people who have never studied a subject pretend to be experts on it in
cases like these?

PamW

[girl gone mad]

37. Nope. Looks like I was right.

And, of course, the chain reactions IAEA was reporting are a really big problem. They will dramatically increase the level of radioactivity the workers are being exposed to. Nice that you can be so nonchalant about other people's lives.

[flamingdem]

41. bingo, seems like industry people need to hit the physics books more often nt

[PamW]

51. Oh please....

bingo, seems like industry people need to hit the physics books more often
===========================

You don't know anything about this - so how can you judge who is right and who is wrong.

The other poster is 100% wrong!

Spontaneous fission can cause fissions, and those fissions can cause even more in a
finite lenght chain.

Where BOTH of you are wrong is that a finite chain is NOT a "criticality".
A "criticality", or being "critical" is very precisely defined, and results not in a
finite chain of fissions, but a self-sustaining chain that can sustain itself as long
as there is fuel to fission. Specifically, it is the precise set of materials and
geometry that makes the Boltzmann transport eigenvalue equation singular. ( If the
equation is not singular, there is only one solution. Since the eigenvalue equation
is homogeneous, ZERO is always a solution. If you don't have a singular equation to
permit multiple solutions, then ZERO must be the only solution. )

That is NOT what is happening here, and is NOT what happened at Chernobyl.

You two are tossing around and using terms that you don't know the meaning of.
Hence, the state of your confusion and errors.

PamW

[Fledermaus]

14. Would the lighter elements float to the top? and the denser ones sink to the bottom?

[AtheistCrusader]

18. I would imagine somewhat if truly molten.

That's just a guess, but I would think at least to a degree. But these metals probably can alloy, so they won't separate like water and oil.

[PamW]

33. Use your own experience.

Use your own experience.

Consider a glass of salt water.

Does the hydrogen float to the top, followed by a layer of oxygen, followed
by a layer of sodium and with a layer of chlorine on the bottom?

NOPE!

PamW

[PamW]

34. Sorry - but NO!!!

If we are talking about gobs of melted nuclear fuel flowing together into increasing masses of fissionable material, the rate of reactions (fission) will vary throughout, and some of these globs can become critical.
======================================

You don't get a self-sustaining criticality in a pool of melted fuel.

The reactor when it is operating counts on the heterogenity of the assembly. That is
the fast neutrons can escape the fuel into the coolant / moderator which is water and
slow down through the resonance region away from the uranium which is a resonance absorber.

Once the neutron has thermalized, it can then re-enter the fuel and cause a fission.

However, the neutrons in a homogeneous molten mass can't escape the U-238 which comprises
the bulk of the material, as a resonance absorber.

Homogeneous molten reactor material won't sustain chain reactions.

PamW

[girl gone mad]

35. "Homogeneous molten reactor material won't sustain chain reactions."

Bullshit.

It happened in the corium at Chernobyl.

"Chain reaction and corresponding increased heat production may progress in parts of the corium if a critical mass can be achieved locally. This condition can be detected by presence of short-life fission products long after the meltdown, in amounts too high to be remaining from the controlled reaction inside the pre-meltdown reactor. As chain reactions generate high amounts of heat and fresh, highly radioactive fission products, this condition is highly undesirable"

http://en.wikipedia.org/wiki/Corium_%28nuclear_reactor%29

And you call yourself an expert? Scary. I've only had about 20 credit hours that would qualify as specifically involving nuclear energy and fissile materials, and even I know better.

[FBaggins]

38. All that you've proven here...

...is that you obviously can't even count to 20.

You didn't even know that Chernobyl "got back to critical" a week ago and now you're telling others what happened?

Please... my sides can't take any more. :rofl:

[girl gone mad]

44. I'm pretty sure I was right about Chernobyl.

If you know how to read graphs, you can clearly see that the core did heat up again days after the initial explosion, despite never getting back to full critical or going super critical.



As I've tried to explain over and over, failure to control decay heat will lead to the fuel expanding, cracking and ultimately melting out of configuration. If the melting fuel collects into a critical mass, the ongoing spontaneous fission will result in sustained induced fission, which will add significant heat to the system and lead to a large release of fission products.

At Chernobyl, the workers reported an "ozone smell" and a blue glow, and also detected significant amounts of short-lived fission products. I get this information from the same book I got the graph above from, called "Chernobyl: A Technical Appraisal", published by the British Nuclear Energy Society.

In a boiling water reactor, the re-flooding of an overheating core can also cause inadvertent criticalities (chain reactions, sustained fission, or whichever terminology you prefer), even if the fuel hasn't melted. You can read the study I posted earlier if you want to understand how and why.

[FBaggins]

45. Which time? Your take on Chernobyl has changed more than once.

If you know how to read graphs, you can clearly see that the core did heat up again days after the initial explosion,

The graph isn't the issue. There's no data there... it's a graphical depiction of someone's theory. But that isn't the point, because I wasn't saying what did or didn't happen at Chernobyl... I was just pointing out that you didn't know a week or two ago and now you're acting as if you've got a handle on it and have all along. This is your contant M.O. - start in ignorance while accusing others of not knowing what they're talking about... then learn a little on google while insisting that you always knew it (and that others must now be catching on), then take on the opposite position while pretending that it was the one you've always held.

As I've tried to explain over and over, failure to control decay heat will lead to the fuel expanding, cracking and ultimately melting out of configuration.

Are you serious? How on earth do you hope to get away with such brazen spinning? You started off by insisting that decay heat couldn't possibly cause a meltdown... and NOW you're trying to claim that you've said "over and over" that decay heat WILL do so?

Are you just hoping that nobody has been paying attention?

If the melting fuel collects into a critical mass, the ongoing spontaneous fission will result in sustained induced fission,

Still badly wrong. If just the wrong set of circumstances occur it's theoretically possible. It's not "will result"... it's not even "in 5% of cases"... it's a number very slightly above zero.

In a boiling water reactor, the re-flooding of an overheating core can also cause inadvertent criticalities

These reactors have been "re-flooded" for over two weeks now. It didn't happen.


chain reactions, sustained fission, or whichever terminology you prefer

Whichever I preffer? Those are not the same thing. I preffer to use them where they actually belong... not as interchangable.

[PamW]

47. The operative word is "IF"

If the melting fuel collects into a critical mass, ....
=========================================================

IF the melting fuel collects into a critical mass...

That's a pretty big IF. As another poster pointed out, you evidently don't
understand the concepts of "homegenity" and "sustained".

If you have something happening only in one spot, then it's not homogeneous.

If you have a small spurt of fissions due to spontaneous fissions, then it
is not self-sustaining.

Again, the only thing you have is a big IF.

Tell you what. Why don't you "if" in one hand, and spit in the other,
and then tell me which hand you have the most of.

PamW

[caraher]

39. What do "homeogeneous" and "sustain" mean to you?

Your Wikipedia quote merely states that *IF* a critical mass can be achieved locally, you'd get a chain reaction, and mentions signatures of such an event. Sure... I don't think anyone would disagree. But this scarcely contradicts the claim you quote because "local" critical mass clearly implies an inhomogeneity that that allows criticality. And it's not clear how long would this chain reaction last in any event.

More to the point, what evidence exists for your claim that this actually happened at Chernobyl? I read the section of the Wikipedia article on corium and didn't see that claim anywhere.

[girl gone mad]

40. I'm not the one who brought up "homogoneous"..

PamW threw that in there. You'll have to ask her what she meant by it and why chose to add this modifier to the "globs of fuel" I was describing. My guess was that she wrongly assumed the molten fuel would immediately homogenize - into what or with what, I'm not clear. Doesn't really matter, does it, because what's essential is the mass of the fuel.

I interpreted "sustained" to mean self-sustained. Meaning a chain reaction without an external neutron source.

I fully stand by my assertions. You can get sustained chain reactions if the melted fuel achieves critical mass. It will generate heat and radiation and it is a significant event.

Spontaneous fission can lead to induced fission and chain reactions. It's possible to have recriticality (or recriticalities) within the core originating from spontaneous fission. It's even possible to get back to high levels of steady-state power, whether or not the fuel melts. Computer simulations have clearly demonstrated the means by which this can occur. These criticalities will generate heat and lead to increased radioactivity.

Nothing the supposed nuclear experts in this thread have claimed has turned out to be accurate so far.

eta: I believe the corium at Chernobyl contained pockets of fission based on the fission products that were being detected weeks after the initial event. I don't have this information handy, so you can discard it if you prefer. It isn't key to the point I was trying to make.

[FBaggins]

43. "Doesn't really matter, does it, because what's essential is the mass of the fuel."

You can add that to the list.

Going to need a new notebook soon.

I fully stand by my assertions.

Yes... we long ago realized that "don't confuse me with the facts... I've already made up my mind" is your standard M.O.

In reality (you should visit some time), you've been badly wrong on at least a dozen seperate issues. Errors that have been pointed out to you and that you've been unable to defend... you just move on to your next claim that others don't know what they've talking about and pretend that you've debated honestly.

You can get sustained chain reactions if the melted fuel achieves critical mass.

What's your definition of "sustained"?

It will generate heat and radiation and it is a significant event.

How much heat? Care to quantify it?


Nothing the supposed nuclear experts in this thread have claimed has turned out to be accurate so far.


Nothing, eh? :rofl:

[PamW]

48. No wonder you are so bad at science - you make up your own meanings..

I interpreted "sustained" to mean self-sustained. Meaning a chain reaction without an external neutron source.
============================================================================

No wonder you are so bad at science, you make up your own meanings for well-defined words and concepts.

"Sustained" or "self-sustaining" means a reaction that can keep itself going.

If you have spontaneous fissions that trigger a chain of other fissions that eventually dies out,
then that is not self-sustaining and the system is therefore sub-critical and not critical.

I assure you, little one, that ALL the inaccuracies have been on YOUR part.

You are not expert at neutronics and transport theory. You know a little, but then make extrapolations
and conjectures that are way over your limited degree of expertise.

PamW

[FBaggins]

50. Nope. She didn't have ALL of the inaccuracies.

For some reason, I remembered nuclear decay as a distinct category from nuclear reactions. My rule of thumb was that the nucleus has to react with something to be a nuclear "reaction". So I corrected her several days ago for lumping the two into one category.

So she didn't have ALL of them.

She has all but one. :)

[PamW]

52. OK - it may not be a shutout...

She has all but one.
=====================

OK - it may not be a shutout....

However, her demonstrated command of the subject material here is virtually nonexistent.

She has all the qualities of the non-scientist. A scientist is precise, and has clear
definitions to terms.

Her attempt at science is fuzzy, with ill-defined terms and concepts.

She's more a political "scientist". She's attempting to make a political statement
and has glommed on the trappings of science in a vain attempt to make her political
statement credible.

It would be more honest just to state that one's political views are one's political
views, and leave it at that. Attempting to use science to give a false sense of
credibility is appalling.

PamW

[PamW]

46. Evidently you need to study more....

And you call yourself an expert? Scary. I've only had about 20 credit hours that would qualify as specifically involving nuclear energy and fissile materials, and even I know better.
======================================

Evidently you need to study more. You evidently haven't learned about the parameter known as
"k-infinity". The "k-infinity" of a molten mass is less than unity.

Yes - I am an expert. My specialty is Transport Theory and solving the Boltzmann transport equation.

Ever here of the concept of "knowing just enough to be dangerous"? It means you know only enough to
think that you know a lot about something when you really don't.

At this point, you "know just enough to be wrong".

PamW

[FBaggins]

6. Ok.

Only flaw in this argument is that once it tunnels through primary containment vessel, it allows a further reduction in the water level which is what is covering the remaining part of the fuel rods -

That assumes that the water level outside of the RPV (not "primary containment" - that's the concrete shell) is not higher than the water level inside.

Considering that the secondary containment has confirmed cracks,

The secondary containment (the outer shell of the building) has great big holes in it, but I suspect that you mean the primary containment. No, I don't know that we know that it has great big holes in it. The pressure suppression chamber does, but that's not the same thing.

As water hits the slag, it will release larger amounts of hydrogen

It isn't the heat that produces the hydrogen, it's the oxidation of the zirconium cladding... which would no longer be on the outside of the fuel, but (at worst) mixed in with the "slag".

which can (if not vented vigorously) cause another explosion

Without the presence of oxygen?

Either way, this is an exercise in "what might have happened". The temperature in unit #2 hasn't indicated that there's anything "burning through" and we haven't seen massive jets of steam or explosions from water hitting molten slag uranium. IF some molten fuel got through the bottom of the RPV, it wasn't much, and it cooled fast enough that there is merely a "leak" - not a vessel that's unable to hold water at all.

[AtheistCrusader]

8. Apparently Corium can release hydrogen from concrete during initial meltdown.

One would think they planned for this, but... Who knows.

I have faith in the containment vessel overall, but if the suppression pool on #2 is actually damaged, all bets are off if large quantities of hydrogen are added to the system.

[Fledermaus]

10. What will happen in the spent fuel pools? Will it not melt as well?

[CJvR]

23. It shouldn't.

It is older, some of it much older. It generates far less heat, indeed the pools should not need any cooling as designed IIRC. It seems however as if they have been overstocked. Also any rods just out of the reactor (if there are any) will be as hot as the stuff remaining inside so a few of them might melt if the pool drains. In addition to cooling the water also acts as radiation protection, without it it becomes more dangerous to work in the area.

[Yo_Mama]

17. Just gallows humor

Molten nuclear fuel can never be described as "good". "Preferable to the alternative" I can handle. "Good" just makes me burst into nervous laughter.

[flamingdem]

19. I know what you mean

.. I really should have used the sarcasm button on the OP but I was in a fit of nervous laughter! Also, I was trying not to post pictures from the movie "The Blob". Oh, when life imitates art.

[xsirdd]

21. Don't worry, (inco)cienze is with us....

Next show still prepared by G.W., Vlad, Tony, Jacques, East tigers, Nirvana cows .... http://en.wikipedia.org/wiki/ITER

[FBaggins]

49. Deleted

Wrong reply.