Discover Magazine

Is there a five-mile-wide ball of hellaciously hot uranium seething at the center of the Earth? If so, how is this Natural Nuclear reaction set off? Could dark matter actually be huge spheres of matter that just couldn't get that fire started?

Click here to find out what I found. (http://www.pnas.org/cgi/reprint/98/20/11085.pdf)

What if the earth lost it's magnetic field for a while? What would the earth be like? I know that it is believed that some animals such as birds use the earths magnetic field for navigation. Would birds loose their way? What other things would happen?

Another great link: NuclearPlanet.com (http://www.nuclearplanet.com/)

Why not?

The heaviest elements sink to the bottom. I actually find it surprising that we find things like Uranium so close to the surface.

As for the magnetic field, the biggest effect is to safeguard the Earth's atmosphere from the solar wind (and other sundry cosmic radiation.) Without our magnetosphere, Earth would have lost much of its gaseous envelope and probably would be a lot more like Mars.

So how do we protect the masses from cosmic death. That would suck ass for everyone to die yike dat.

Some possible ideas...

Leave earth
or we could
Leave earth
or maybe even....
Nano shields up.

Seriously though, Shields up!! Shields up!!!

heh

Originally posted by Pine_net
Seriously though, Shields up!! Shields up!!!

Embrace the Force, Luke... :D

Wait.. Does Uranium even exist naturally?

Normally everything except Gold, Platnum and Diamond oxidize over time (there may be other elements that do not, I can not remember...).

So Uranium is found as Uranium Oxide. Volcanic eruptions might pump out elemental Uranium and Thorium too...

That's about the dumbest damn thing I've read all day.

If you seriously believe that the earth's core is a giant natural nuclear reactor then you should be posting in the SciFi forum.








(what in the world causes people to believe such BS?!?!?!? :confused: )

Ah...ummm...welll...cough cough...

The Discover Magazine??? Check out their website...

AUGUST 2002 HIGHLIGHTS
COVER STORY
Nuclear Planet By Brad Lemley
Geophysicists have long assumed that the center of Earth is just a big hot ball of iron and nickel. But a bold new theory suggests we are perched atop a gigantic fission reactor fueled by a five-mile-wide core of solid uranium.

Nuclear Planet

Is there a five-mile-wide ball of hellaciously hot uranium seething at the center of the Earth?

By Brad Lemley


What is Earth? Poets say it's a celestial sapphire, a cerulean orb. Astronomers say it's a medium-size planet orbiting an average star. Some environmentalists say it's Mother. Biologists say it's life's only known home. But the most scientifically precise definition may prove to be the one that no one suspected. Earth, says geophysicist J. Marvin Herndon, is a gigantic natural nuclear power plant. We live on its thick shield, while 4,000 miles below our feet a five-mile-wide ball of uranium burns, churns, and reacts, creating the planet's magnetic field as well as the heat that powers volcanoes and continental-plate movements. Herndon's theory boldly contradicts the view that has dominated geophysics since the 1940s: that Earth's inner core is a huge ball of partially crystallized iron and nickel, slowly cooling and growing as it surrenders heat into a fluid core. Radioactivity, in this model, is just a supplementary heat source, with widely dispersed isotopes decaying on their own, not concentrated.

Full text of this article can be found in the current issue of Discover Magazine.

http://www.nuclearplanet.com/dismaga.jpg

Scientific Papers by J. Marvin Herndon on Planetary Nuclear Fission Reactors

J. M. Herndon (1992) Nuclear fission reactors as energy sources for the giant outer planets. Published in English in the German journal, Naturwissenschaften, vol. 79, pp 7-14.

J. M. Herndon (1993) Feasibility of a nuclear fission reactor at the center of the earth as the energy source for the geomagnetic field. Published in English in the Japanese journal, Journal of Geomagnetism and Geoelectricity, vol. 45, pp 423-437.

J. M. Herndon (1994) Planetary and protostellar nuclear fission; implications for planetary change, stellar ignition and dark matter. Published in the British journal, Proceedings of the Royal Society of London, series A, vol. 445, pp. 453-461.

J. M. Herndon (1996) Sub-structure of the inner core of the earth. Published in the American journal, Proceedings of the National Academy of Sciences (USA), vol. 93, pp. 646-648.

J. M. Herndon (1998) Composition of the deep interior of the earth: divergent geophysical development with fundamentally different geophysical implications. Published in English in the international journal, Physics of the Earth and Planetary Interiors, vol. 105, p.1-4.

J. M. Herndon (1998) Examining the overlooked implications of natural nuclear reactors. Published in the American journal, Eos, Transactions of the American Geophysical Union, vol. 79, no. 38, pp. 451, 456. [see text]

D. F. Hollenbach and J. M. Herndon (2001) Deep-earth reactor: nuclear fission, helium, and the geomagnetic field. Published in the American journal, Proceedings of the National Academy of Sciences (USA), vol. 98, no. 20, pp. 11085-11090.



Scientific Papers by J. Marvin Herndon on Deep-Earth Composition

J. M. Herndon (1979) The nickel silicide inner core of the Earth. Published in the British journal, Proceedings of the Royal Society of London, series A, vol. 368, pp. 495-500.

J. M. Herndon (1980) The chemical composition of the interior shells of the Earth. Published in the British journal, Proceedings of the Royal Society of London, series A, vol. 372, pp. 149-152.

J. M. Herndon (1982) The object at the centre of the Earth. Published in English in the German journal, Naturwissenschaften, vol. 69, pp 34-37.

J. M. Herndon (1993) Feasibility of a nuclear fission reactor at the center of the earth as the energy source for the geomagnetic field. Published in English in the Japanese journal, Journal of Geomagnetism and Geoelectricity, vol. 45, pp 423-437.

J. M. Herndon (1996) Sub-structure of the inner core of the earth. Published in the American journal, Proceedings of the National Academy of Sciences (USA), vol. 93, pp. 646-648.

J. M. Herndon (1998) Composition of the deep interior of the earth: divergent geophysical development with fundamentally different geophysical implications. Published in English in the international journal, Physics of the Earth and Planetary Interiors, vol. 105, p.1-4.

Hey everyone,
J.M H has a site called: "www.nuclearplanet.com" but he dismissed T.Chalko's theory as "fantastic nonsense" in a letter to me, which can be seen at www.student.unimelb.edu.au/~msephton/coreletters.htm

Oh you mean nonsense like people going to the moon and stuff, WOW the land sure is flat around here. heh heh

:rolleyes:

Perhaps you don't understand. That REALLY IS the dumbest thing I've heard in awhile. I guess you have to have better undertanding of how nuclear reactions and nuclear energy work, but the idea that the core of the earth is a 5 mi diameter sphere of uranium that is a stable nuclear reactor providing energy to the earth is just stupid.

There are far too many factors involved to have a stable nuclear reactor when carefully constructed by us; first thing that comes to mind is moderators. NO WAY all that would occur naturally on that scale (size), in that shape, for this long a period of time, at the core of the earth.

Emfuser,

Why not? Check out the Oklo nuclear reactor, e.g.

http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Lovelock_Oklo.html

That's natural and not engineered by anyone. And, it's right here at the crust's surface.

Now, I doubt you would dispute the fact that the crust is made up of the lightest elements in our planet; the heaviest (like iron) sink to the bottom. Uranium and other heavy elements are much heavier than iron, so why do you think they wouldn't sink even faster and concentrate at the center?

The nucleus of our planet might as well be a site of continuous nuclear explosion over the last few billion years. Why don't we see any effects from this? Well, consider the titanic pressure exerted by the upper layers of the planet! Plus, the surface is insulated from the core by thousands of kilometers of material; this is the ultimate in "underground" nuclear testing. ;) Besides if it weren't for nuclear heat, volcanism might have already ground to a halt by now.

As for possible moderators, consider that any nuclear material in the core is not pure or concentrated; it's still mixed with iron and whatever else is down there. If it gets too concentrated at the core, its temperature will increase so much and so quickly and it will become so much hotter than anything around it that despite its greater weight it would convect upward thus diluting its concentrations and re-mixing with less enriched magma. So this system can easily regulate itself automatically.

NO WAY all that would occur naturally on that scale (size), in that shape, for this long a period of time, at the core of the earth.


The SUN does not exist....it is not natural...on that scale...in that shape...for this long a time....it is a myth....

kmguru,

Technically, the sun is a fusion (as opposed to fission) reactor. :p

Besides, the surface properties of the sun vs. earth are a tad different, no? :D

Discover is an awesome magazine. I read that article. Makes good sense.

I knew it was just a matter of time before someone brought up the Oklo reactor. That's some very cool evidence for natural occurance. I believe the scientists search for Benzine and He3 around volcanic activity is the right way to go. How else could someone prove this claim?

Originally posted by overdoze
Emfuser,

Why not? Check out the Oklo nuclear reactor, e.g.

http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Lovelock_Oklo.html

That's natural and not engineered by anyone. And, it's right here at the crust's surface.

Now, I doubt you would dispute the fact that the crust is made up of the lightest elements in our planet; the heaviest (like iron) sink to the bottom. Uranium and other heavy elements are much heavier than iron, so why do you think they wouldn't sink even faster and concentrate at the center?

:rolleyes: *sigh*
Yes the Oklo reactor is fascinating. Natural Uranium ore with the right amounts of moderator (water and low Z elements) in the right concentrations in a relatively small area ON THE SURFACE.

The core of the earth is a ridiculous scale for a fission reactor, there are no moderators and no refueling, plus the energy created (released) by a natural occurance of that scale (ignoring the other reasons it wouldn't happen) would not be steady state and would definitely have catastrophic effects on the planet far beyond the normal earth activity we see. Such a scale would essentially make a giant bomb out of the earth's core. Nothing that would be continuous, just a really REALLY big bomb.


The nucleus of our planet might as well be a site of continuous nuclear explosion over the last few billion years. Why don't we see any effects from this? Well, consider the titanic pressure exerted by the upper layers of the planet! Plus, the surface is insulated from the core by thousands of kilometers of material; this is the ultimate in "underground" nuclear testing. ;) Besides if it weren't for nuclear heat, volcanism might have already ground to a halt by now.

It sure as hell isn't a continuous nuclear explosion... especially if you're suggesting fusion. Fusion is out of the question here because our core is heavy elements like iron and nickel and those are the elements that destroy stars when they're formed in the core.


As for possible moderators, consider that any nuclear material in the core is not pure or concentrated; it's still mixed with iron and whatever else is down there. If it gets too concentrated at the core, its temperature will increase so much and so quickly and it will become so much hotter than anything around it that despite its greater weight it would convect upward thus diluting its concentrations and re-mixing with less enriched magma. So this system can easily regulate itself automatically.

Ok lets ignore moderators (and every other point, for the sake of arguing this one point). Let's say it's a fast fission system. Now you have the problem of all sorts of transuranics, fission fragments, poisons (like Xe) and "spent" fuel working against the reaction. Not to mention the fact that all the fissionable and fissile elements would've been used up relatively quickly in an even distribution throughout the core.

You obviously don't know enough about the basic principles of nuclear energy (basic reactions, concepts of fast and thermal fission, fuel consumption, etc) for your arguements to hold water. I understand why you're thinking the way you are, and can tell you with a pretty high degree of certainty that it's incorrect, for the most part.

Originally posted by kmguru
The SUN does not exist....it is not natural...on that scale...in that shape...for this long a time....it is a myth....

The sun is mainly composed of light elements and works on F-U-S-I-O-N (http://www.howstuffworks.com/sun.htm). The disucssion at hand appears to be about the suggestion that the earth's core is a giant F-I-S-S-I-O-N reactor (http://www.howstuffworks.com/nuclear-power.htm). Overdoze, you should check those out too.

:)

[QUOTE]The core of the earth is a ridiculous scale for a fission reactor, there are no moderators and no refueling, plus the energy created (released) by a natural occurance of that scale (ignoring the other reasons it wouldn't happen) would not be steady state and would definitely have catastrophic effects on the planet far beyond the normal earth activity we see...QUOTE]

At the pressures that prevail in the Earths core, density is a function almost exclusively of atomic mass and number. Uranium, thorium, and other actinides, being high-temperature precipitates and the densest substances, by the action of gravity, would tend to concentrate, possibly scavenged by other precipitates, ultimately forming a fissionable, critical mass. The same mechanism for concentrating the actinides should cause the lighter fisson products to separate from the heavier actinides, thus helping to maintain a nuclear-reactor-critical configuration.

Originally posted by Emfuser
The core of the earth is a ridiculous scale for a fission reactor,


What's so ridiculous about it? It doesn't even have to be a single fission reactor; there could be many at any one time down there, arising from local chance concentrations of radioactivity.


there are no moderators and no refueling,


There are plenty of moderators (it's all suspended in molten iron), and as for refueling you're right. However, we aren't talking about your normal functional fission reactor. Rather, we're talking about a "fission reactor" in a state of continuous meltdown.


plus the energy created (released) by a natural occurance of that scale (ignoring the other reasons it wouldn't happen) would not be steady state


And why wouldn't it be?


and would definitely have catastrophic effects on the planet far beyond the normal earth activity we see.


And how do you determine that?


Such a scale would essentially make a giant bomb out of the earth's core. Nothing that would be continuous, just a really REALLY big bomb.


Fission reactor meltdowns are not the same as nuke explosions. If you know as much about nuclear processes as you claim, you at least ought to know this much.


It sure as hell isn't a continuous nuclear explosion... especially if you're suggesting fusion.


Good grief, where did that come from? FYI, most of us know the difference between fission and fusion ever since Junior High.


Let's say it's a fast fission system. Now you have the problem of all sorts of transuranics, fission fragments, poisons (like Xe) and "spent" fuel working against the reaction.


They would float up by virtue of being lighter. And the "goal" of the "reactor" is not optimal output. It simply generates a lot of heat over long periods of time, gradually losing its useful nuclear energy stored when the heavy elements were created in a supernova explosion a long time before Earth's formation.


Not to mention the fact that all the fissionable and fissile elements would've been used up relatively quickly in an even distribution throughout the core.


That's perhaps the only strong point of your argument. However, I don't see why this would necessarily happen. It's reasonable to assume that the amount of fissionable and fissile material in the core dwarfs by far any material present in the crust or even the mantle. If there is still fissionable material in the crust after all this time, then there certainly is fissionable material in the core. Not to even mention that most of today's crust has been generated from deeper mantle fairly recently -- i.e. a few hundred million years ago.

Moreover, the material in the core cannot become so concentrated as to produce a catastrophic explosion, because that very heat will tend to disperse the material as soon as it becomes too concentrated. The heat generated by fission would act on radioactive atoms like the charge on positive ions, preventing them from getting too close to each other and tending to distribute them outward around the surface of the core while gravity and currents work to counter that effect. So you have a more or less steady-state, sustained, low-level fission reaction churning within the currents of molten iron in the core for millions and billions of years.


You obviously don't know enough about the basic principles of nuclear energy (basic reactions, concepts of fast and thermal fission, fuel consumption, etc) for your arguements to hold water.


Nobody knows enough. Barrels of radioactive waste, after a few years, contain a mixture of elements and chemicals that is currently unpredictable. Nuclear waste managers actually have to sample the brew to determine what's in it at any particular moment in time; it's impossible to predict the contents theoretically at this stage. Moreover, even low-grade nuclear waste tends to heat up dangerously if it becomes too concentrated or there is too great of a volume. This is not due to any standard nuclear reaction used in fission power plants.


I understand why you're thinking the way you are, and can tell you with a pretty high degree of certainty that it's incorrect, for the most part.


You'll have to show us all where your certainty comes from. I hope the answer is not hubris.

Originally posted by overdoze
What's so ridiculous about it? It doesn't even have to be a single fission reactor; there could be many at any one time down there, arising from local chance concentrations of radioactivity.
What's ridiculous? Ok: Scale, stability (there is none), spikes of energy dissipated out from the core, fuel burnout, reaction poisons.


There are plenty of moderators (it's all suspended in molten iron), and as for refueling you're right. However, we aren't talking about your normal functional fission reactor. Rather, we're talking about a "fission reactor" in a state of continuous meltdown.
Why would there be any low Z elements in the core when they would've, according to you and suggestions of buoyancy, floated to outside the core?


And why wouldn't it be? (steady state)
This is a BIG point. It wouldn't be steady state because steady state is not the nature of nuclear reactions. Given conditions suggested here, you'd have a giant supercritical reactor that would reach some ridiculously large power output in a matter of nanoseconds. This is because power increases in a fission reactor exponentially. This is why it'd be a giant bomb.

Fission reactor meltdowns are not the same as nuke explosions. If you know as much about nuclear processes as you claim, you at least ought to know this much.

This is true for a man-made reactor. Our reactors are carefully constructed and don't have the right geometry or material distribution to be a bomb. That's why they melt down instead of exploding. For the scale we're talking about, such considerations go out the window. The limiting factor in how big we can make a fission bomb is how big a mass (well, two masses) of concentrated fissile nuclei (Pu-239, U-235, et al) we can make before the masses are bombs themselves.


They would float up by virtue of being lighter. And the "goal" of the "reactor" is not optimal output. It simply generates a lot of heat over long periods of time, gradually losing its useful nuclear energy stored when the heavy elements were created in a supernova explosion a long time before Earth's formation.
Eventually they would, but they would be a poison for as long as they're there, and that could be awhile. Creation of such poisons on such a scale would (at best) yield some seriously squirrley (spikey) behavior that would be violently shaking the planet quite often.


Moreover, the material in the core cannot become so concentrated as to produce a catastrophic explosion, because that very heat will tend to disperse the material as soon as it becomes too concentrated. The heat generated by fission would act on radioactive atoms like the charge on positive ions, preventing them from getting too close to each other and tending to distribute them outward around the surface of the core while gravity and currents work to counter that effect. So you have a more or less steady-state, sustained, low-level fission reaction churning within the currents of molten iron in the core for millions and billions of years.

I have no reason to believe that there would be anything but VERY uniform material distribution in the core, given how old the earth is. Heat and material movement might matter on a human scale reactor, but not this size. I'm sure there's some very interesting natural mechanisms for material transport, but nothing that would regulate the reactor as you're suggesting.


Nobody knows enough. Barrels of radioactive waste, after a few years, contain a mixture of elements and chemicals that is currently unpredictable. Nuclear waste managers actually have to sample the brew to determine what's in it at any particular moment in time; it's impossible to predict the contents theoretically at this stage. Moreover, even low-grade nuclear waste tends to heat up dangerously if it becomes too concentrated or there is too great of a volume. This is not due to any standard nuclear reaction used in fission power plants.

It really all depends on if and how you mix waste. Generally, nuclear power doesn't generate much besides some high level waste (spent fuel) and some short lived low level wastes from reactor operation. The reason it is impossible to exactly determine what's in those mixes is because decay chains have more than one possible path. However we can tell with pretty good certainty what should and shouldn't be there.

There are a shitload of rules for doing this and they're followed quite rigidly. Don't get these ideas of leaky barrels of waste killing children at playgrounds get to your head. The only irresponsible waste disposal done that I know of was by the government (for weapons development and production during the cold war) before people started getting on their asses. Such messes have nothing to do with present nuclear power production and are nothing I wish to associate myself with.


You'll have to show us all where your certainty comes from. I hope the answer is not hubris.
No problem. How's this:
http://www.imagestation.com/picture/sraid25/p8eefce7e9a2e63867adbc2df25297c84/fd8ef91d.jpg
This is me.

Originally posted by Emfuser
No problem. How's this:


And here I thought your 20 years in Los Alamos and 15 years at GE....:D

Originally posted by Emfuser
What's ridiculous? Ok: Scale, stability (there is none), spikes of energy dissipated out from the core, fuel burnout, reaction poisons.


Scale: you ought to know that no sustained fission reaction can occur across kilometers of molten iron. Obviously, most of the fission hot-spots (when there are any) will be localized and would coalesce/dissipate in a random way. The rest would take the form of a constant, low-level radiation/heat background. And as for stability, in the long term the noise averages out. That's stability.


Why would there be any low Z elements in the core when they would've, according to you and suggestions of buoyancy, floated to outside the core?


If there were no convection, turbulence and other hydroelectrodynamic currents induced by Earth's rotation, then you would be correct.


Given conditions suggested here, you'd have a giant supercritical reactor that would reach some ridiculously large power output in a matter of nanoseconds.


Why supercritical? Why giant?


This is because power increases in a fission reactor exponentially. This is why it'd be a giant bomb.


This assumes there is a sufficient density of fissile material to begin with. If, as soon as the density reaches critical levels, there is an exponential build up of heat, then this heat will prevent the density becoming critical to begin with. You keep assuming some artificial initial conditions; newsflash: there's nothing artificial about our planet's core. Conditions in the core at any instant in time must have been generated causally by immediately preceding conditions in the core. You are proposing naturally impossible conditions as the starting point of your analysis.


Our reactors are carefully constructed and don't have the right geometry or material distribution to be a bomb. That's why they melt down instead of exploding.


That is baloney, and I would have expected better from a so-called nuclear engineer.

Our reactors do not contain the right fuel to be a bomb; bomb-grade material is highly enriched and purified -- conditions one would definitely not expect in nature and that take some pretty esoteric machinery and a lot of effort to achieve. Unless the material is bomb-grade, it won't sustain a runaway chain reaction no matter how much of it you put together. Fill the oceans with it; all you'll get is a massive meltdown but no nuclear blast.


For the scale we're talking about, such considerations go out the window. The limiting factor in how big we can make a fission bomb is how big a mass (well, two masses) of concentrated fissile nuclei (Pu-239, U-235, et al) we can make before the masses are bombs themselves.


And you should know this is not applicable in a natural setting.


Eventually they would, but they would be a poison for as long as they're there, and that could be awhile.


Which is yet another argument against your catastrophic visions.


Creation of such poisons on such a scale would (at best) yield some seriously squirrley (spikey) behavior that would be violently shaking the planet quite often.


Do you seriously propose that such tiny spikes of energy would be sufficient to be felt through thousands of kilometers of turbulent liquid rock of varying compositions and densities? Then again, the surface of our planet is constantly, incessantly shaking. The vibrations are just too week for us to feel, but they do present a noise background with which seismologists must cope.

Besides, keep in mind that the inside of our planet is always in motion, and it would be pretty hard to create some steady-state nuclear phenomenon in such an environment. At best all you'd get is transient spikes.


I have no reason to believe that there would be anything but VERY uniform material distribution in the core, given how old the earth is.


Ah, now you want to consider long-term trends for a change. But this time, you ignore the dynamism of the core. Just answer these questions: where does the geomagnetic field come from, and how does it manage to reverse itself every few thousand years?


Heat and material movement might matter on a human scale reactor, but not this size.


Why not "this size"? It would take longer to assemble a local inhomogeneity of a "reactor", than it would take to blow it apart.


It really all depends on if and how you mix waste. Generally, nuclear power doesn't generate much besides some high level waste (spent fuel) and some short lived low level wastes from reactor operation. ... There are a shitload of rules for doing this and they're followed quite rigidly. ... Such messes have nothing to do with present nuclear power production and are nothing I wish to associate myself with.


Last I checked we weren't talking about human management of nuclear plants, but about the natural mixtures and transmutations that would occur under intense pressure and temperature deep in the Earth's core that together are hardly attainable in a laboratory for any significant period of time. The point was that a great many nuclear pathways would play a role, and there would be many different avenues for producing heat through nuclear reactions.


http://www.imagestation.com/picture/sraid25/p8eefce7e9a2e63867adbc2df25297c84/fd8ef91d.jpg
This is me.


Congratulations. But the guys who wrote the original article at the start of this thread are PhDs; one of them working at Oak Ridge National Laboratory. So it seems you're screwed. :rolleyes:

Besides, if I didn't know better I would have concluded that you were attempting to argue from authority. That would have been very bad form.

May I introduce a couple of moderators namely Zirconium and Hafnium that may play major roles in the reactor too. And we have plenty of them.

I just read the whole article (skimmed it last time) and I can say that I'm still quite comfortable with my position. They made too many assumptions and used a very limited simulation method(s).

Originally posted by overdoze
Scale: you ought to know that no sustained fission reaction can occur across kilometers of molten iron. Obviously, most of the fission hot-spots (when there are any) will be localized and would coalesce/dissipate in a random way. The rest would take the form of a constant, low-level radiation/heat background. And as for stability, in the long term the noise averages out. That's stability.

Ah ah ah... the article you're so vehemently defending suggest a core mass spread across several km of core. Further more it insisted on modeling for constant operation during the past 2 billion years. THAT is why is said scale.


If there were no convection, turbulence and other hydroelectrodynamic currents induced by Earth's rotation, then you would be correct.
The article mentioned outward movement of the lighter elements, poisons and such, but ADMITTED that if their ASSUMPTION was wrong that much of their argument goes to shit.

Why supercritical? Why giant?
Supercritical: k (k_eff in this case) > 1.0000
The graph on the first column of the third page suggests constant supercriticality.

Giant: compared to the reactors we build and the codes they're using that were designed with man-made sized reactors in mind, this scale is gigantic.


This assumes there is a sufficient density of fissile material to begin with. If, as soon as the density reaches critical levels, there is an exponential build up of heat, then this heat will prevent the density becoming critical to begin with. You keep assuming some artificial initial conditions; newsflash: there's nothing artificial about our planet's core. Conditions in the core at any instant in time must have been generated causally by immediately preceding conditions in the core. You are proposing naturally impossible conditions as the starting point of your analysis.
There has to be sufficient density of fuel to begin with for there to be a reactor. That's not an assumption, it's a given. There's no artificial condition here, having a sufficient amount of material is necessary for there to be any nuclear reactor.

That is baloney, and I would have expected better from a so-called nuclear engineer.


Our reactors do not contain the right fuel to be a bomb; bomb-grade material is highly enriched and purified -- conditions one would definitely not expect in nature and that take some pretty esoteric machinery and a lot of effort to achieve. Unless the material is bomb-grade, it won't sustain a runaway chain reaction no matter how much of it you put together. Fill the oceans with it; all you'll get is a massive meltdown but no nuclear blast.

Oh for pete's sake. I said:
Originally said by me
Our reactors are carefully constructed and don't have the right geometry or material distribution
Material distribution AKA number density AKA fuel enrichment. I understand perfectly well the enrichment differences between reactor grade fuel and bomb grade fuel. Quit splitting fine hairs with this crap, you're wasting your time and mine.


And you should know this is not applicable in a natural setting.

Why? As far as reactor (or bomb) function is concerned, a concentrated mass of Uranium made by man is no different than one that forms naturally. You can only screw around with varying density and size so much before you reach the limits.


Do you seriously propose that such tiny spikes of energy would be sufficient to be felt through thousands of kilometers of turbulent liquid rock of varying compositions and densities? Then again, the surface of our planet is constantly, incessantly shaking. The vibrations are just too week for us to feel, but they do present a noise background with which seismologists must cope.
TINY?!?!?! When you're talking about a reactor that is forced (by gravitational pressure) to remain a relatively constant volume undergoing the HUGE power spikes that occur in nuclear reactors (power can vary by as much as 3 orders of magnitude in MAN-MADE reactors left unchecked) left unchecked. This thing is (supposedly) operating in the range of anywhere from 3-45 TW in their assumed normal conditions, the spikes would release several times that much energy over a short period of time. I'm not claiming to know exactly what would happen, but dissipating that much energy (especially when it's still at the core) is bound to cause problems.


Besides, keep in mind that the inside of our planet is always in motion, and it would be pretty hard to create some steady-state nuclear phenomenon in such an environment. At best all you'd get is transient spikes.

Like I said before, if you want to argue for the article, you have to keep along their position that the reactor operates over a period of some 2 billion years. You don't know enough about nuclear energy to just take their idea and run with it.


Ah, now you want to consider long-term trends for a change. But this time, you ignore the dynamism of the core. Just answer these questions: where does the geomagnetic field come from, and how does it manage to reverse itself every few thousand years?
From the National Geophysical data center:
a. the Earth's conducting, fluid outer core (~90%);
b. magnetized rocks in Earth's crust;
c. fields generated outside Earth by electric currents flowing in the ionosphere and magnetosphere,
d. electric currents flowing in the Earth's crust (usually induced by varying external magnetic fields), and
e. ocean current effects
(I actually was able to think of a, c, and e beforehand thanks to all those fusion classes I took. :D )
I think that, given those conditions (variables), the appropriate question would be "why would it remain constant?" Easy answer: it doesn't.


Why not "this size"? It would take longer to assemble a local inhomogeneity of a "reactor", than it would take to blow it apart.

Because size here also has to deal with scale and number density. On a human scale, such concentrations get blown apart; on this scale, everything is pretty much stuck in place because of the immense pressure. Rapidly rising criticality would be a big problem AKA nasty spike in k. As my first neutronics professor would say (he's Korean) "you just turn your reactor into bomb... only result will be boom!"


Last I checked we weren't talking about human management of nuclear plants, but about the natural mixtures and transmutations that would occur under intense pressure and temperature deep in the Earth's core that together are hardly attainable in a laboratory for any significant period of time. The point was that a great many nuclear pathways would play a role, and there would be many different avenues for producing heat through nuclear reactions.

We're not talking about human management of nuclear plants, however, periodic comparison is useful for certain considerations.

We obviously cannot replicate such conditions and that brings around all the assumptions they made with modeling. Simply put, there were too many. They made enough assumptions to reduce a vastly complex problem to something out of an introductory neutronics class. The codes they used were not meant for this scale or environment and 1-D analysis doesn't hold much weight for any real considerations even where relative homogeneity can be attained. They made too many assumptions and simplified the problem too much to make it anything more than a HW assignment for a dual level class.

Congratulations. But the guys who wrote the original article at the start of this thread are PhDs; one of them working at Oak Ridge National Laboratory. So it seems you're screwed. :rolleyes:


Hey pal, there's no need to be rude. You asked me to show why I'm qualified to get in this debate with the certainty I have and I showed you. Also, just because they have Ph.Ds in something doesn't automatically make them experts. Based on their paper, I'd say it's likely that my neutronics education is on par with or possibly even exceeds theirs. The difference between a B.S. and a Ph.D is a thesis that proves the Ph.D. can do research. Another consideration is what those Ph.Ds are in. A physicist's Ph.D is pretty different from a nuclear engineer's Ph.D. I'd be pretty surprised if their Ph.Ds were nuclear engineering because nukes should know better.


Besides, if I didn't know better I would have concluded that you were attempting to argue from authority. That would have been very bad form.
I don't quite follow what you're trying to say.

Well, now that I have also read the article carefully ;), I won't support it so strongly.

However, I think their general approach is valid. You can't create ultra-complex models right away without going through simpler stages first. Simplified models help you get a grip on what's going on, and then ratcheting up complexity gradually might show predictable trends that would allow extrapolation or at least constrain the possibilities.

Now, I would think it pretty much indisputable that heavier elements sink. Further, it ought to be a no-brainer that most of the Uranium/Thorium/whatever would have sunk to the center and what we see at the surface is mere traces compared to concentrations at/near the core. What exact shape this would take and what the equilibrium would look like or how stable it would be may be up for debate, but it is pretty obvious that old (crystallized iron core) models don't take the radiological elements seriously at all. Moreover, with estimated 10 TW still escaping the Earth (what is it, hourly?) today, one has to wonder how it's overwhelmingly molten after 4 billion years.

The authors admit the limitations of their model, and they would clearly like to include more accurate transport and hydrodynamics into it. I'm sure that's the next step. But I think their ³He observation is intriguing, and their suggestions for further empirical testing are quite reasonable. I think they overdid the supercriticality bit; I find it easier to imagine that k_eff would approach 1 from below, not above, as the "reactor" oscillates between activation due to gravitationally driven diffusion and shutdown due to thermal expansion/convection/accumulation of moderators/poisons. That's probably what they'll see when they make their model more realistic.

Concerning magnetic field, you did mention that 90% is attributed to the core. Any other contributions hardly could destabilize the field; major changes can only be due to the dynamics of the core one way or some other.

To consider dissipation of energy, let's say a 300 kiloton nuclear device dissipates roughly 10¹² J of energy. That's 1 TJ. For convenience, suppose all this energy is released within 1/10th of a second; then it's 10 TW of power. Then it would take the energy of, say 10 300 kiloton nuclear devices to output 100 TW. Crude, I know, but bear with me. In 1953, I believe, the Russians tested a 5 megaton fission bomb. That's the equivalent of 10 500 kiloton nuclear devices. The world would have been none the wiser if it weren't for sensitive seismometers and, of course, spies. Parenthetically, typical fusion bombs today can reach upward of 50 megaton output, which is another factor of 10 larger. Now, even 100 TW spikes in the core would happen some 5000 kilometers down under ground or so, and would be masked by multiple inhomogeneous layers of liquid, semi-liquid and solid rock of various compositions. Let's just assume this extra energy would take the shape of a sound wave (note: in a typical earthquake, only 10% of the energy is manifested as seismic waves; the rest goes into actually deforming the crust.) Assuming losses due to friction, reflection/refraction, and simple heat absorption, how much of that explosive energy would actually reach the surface? Over how large a surface area would it be spread? Would it be at all detectable on the surface? What do you think? A magnitude 8 (Richter scale) earthquake releases energy equivalent of roughly 1 gigaton of TNT. At 100 km depth it is devastating. At 1000 km depth it is barely detectable. At 5000 km depth it is a whimper buried in the noise. To compound the problem, for shockwaves originating that deep I'd expect most of the energy to reflect back into the core from the various liquid/solid boundaries, so that only a tinsy fraction of that energy would reach the surface as a sound wave (the rest would eventually reach the surface as heat.)

So to sum up, you need to put the "enormity" of the "reactor" into perspective. Earth is a pretty enormous planet, and it takes some truly titanic energies to rock it (horrible pun not intended.) Plus, take the dynamism of the core into account. Things might be easier to model as symmetrical and static, but in real life hardly anything ever is that simple.

im not really on the side of the article........ but 2 points in the inanity of this 'my dick is bigger than yours' contest.........




since when is the earth @ steady-state?

......


and more importantly.........


haven't you ever solved the actual spherical PDE's on autocatalytic phenomena by hand? (since you supposedly have a degree in N.E.)..... i mean hell, i did it just as a math exercise....
clearly, the assumed density profile would not allow for a bomb effect, perhaps however, you have some refined first hand knowledge of core composition etc that you aren't revealing........

Quoted from http://www.nuclearplanet.com/ (http://www.nuclearplanet.com/eos_paper.htm)

Eos, Transactions, American Geophysical Union, Vol. 79, No. 38, September 22,1998, Pages 451,456

QUOTE:

Unlike traditional, globally important energy sources, which change gradually and in only one direction overtime, planetary-scale nuclear fission reactors may be capable of variable or intermittent operation like the Oklo reactors. As inferred from Oklo and reactor technology, changes in nuclear reactor energy production can result from changes in composition and/or position of fuel, moderators, and neutron absorbers. Paleomagnetic investigations (augmented by geological, paleobiological, and geochronological studies) and magnetometer measurements of the ocean floor have established that the Earth's magnetic field reverses polarity frequently, but quite irregularly, with an average time between reversals of about 200,000 years. The cause of geomagnetic reversals has not yet been established. Herndon [ 1993] has suggested that the variable and intermittent changes in the intensity and direction of the geomagnetic field have their origin in nuclear reactor variability.

Significantly, the geomagnetic field has been in existence at least 3000 million years and certainly during the time period natural reactors could begin to operate and breed fissile material. The following schematically illustrates one possible mechanism for geomagnetic field reversals and excursions:

Nuclear fission consumes actinide fuel and produces fission fragments, some of which have high neutron capture cross-sections. Fission products may be removed from the reactor sub-core region by diffusion and gravitational layering based on density at the prevailing pressures. One might imagine instances in which the rate of production of fission fragments exceeds the rate of their removal. In such instances, the power output of the reactor would decrease and the reactor might shut down, eventually shutting down the Earth's magnetic field. After a period of time had elapsed for fission fragments to diffuse to regions of lower density, the reactor output would increase, and the Earth's magnetic field would reestablish itself either in the same direction or in the reverse direction.

Ok... people are sounding more reasonable now. :)

I think these guys have an interesting idea, but their assumptions and limited modeling are the limiting factors as far as any real validity is concerned.

I think the idea that OCASSIONAL, short lived, natural critical masses could form is worth considering, but the idea that the core is a big reactor just raises too many questions that nobody can really answer.

Good discussion. :)

Let's assume it's true. Wouldn't it continually breed plutonium? If so, where'd it go? If we assume as some here do that it would “float” to the center – well, that doesn’t seem like too pretty a picture. If we more appropriately assume that most heavy elements more or less mix proportionately at or near the center (due to the equal or almost equal effect of gravity originating from all sides) then the theory goes completely out the door as there would be no gravity driven conjugation of the uranium in the first place.

I gotta pour me a nice tall glass of skepticism here.

Surely there needs only to be gravity driven conjugation of fissionable materials, those are ones that can be "split" by neutrons for this theory to be important. This site, http://www.isis-online.org/publications/fmct/primer/Section_I.html, mentions that such materials include plutonium 239 and uranium 235.
According to www.environmentalchemistry.com, Plutonium is more dense than Uranium. So it would be expected to move more easily towards the centre in the case where the nuclear material actually differentiates as Herndon has suggested, and as participants here were inclined to agree about to a limited extent.
However also I have noted that according to www.environmentalchemistry.com, some Plutonium nuclides are parent nuclides for Uranium isotopes. According to that site this means that by radioactive decay they turn into Uranium nuclides.

However bobbapink seems to have a confident criticism.
What is the basis of confidently claiming that there the set of high density substances in the core of the earth is not likely to have higher concentration of fissionable materials than normal?

Presently Chalko's article at www.nujournal.net/core.pdf is not available because it is being revised, however it suggested that if you consider the conditions for the stability of the solid inner core in the fluid outer core, it is clear that the density of the inner core should be about 26grams/cm^3. This is higher than the densities of Uranium and Plutonium, and I think Chalko suggested that materials of such density may not have been discovered yet. If this is true, then the way Uranium and Plutonium and substances of similar densities would be likely to intermix and interact in the core may not be important.

My main point is that for these reasons, I am not sure that you should dismiss these theories.

The OKLO reactors only worked since the concentration of U-235 was high enough to permit a light water reactor to function. This was several billion years ago IIRC and since then the U235 concentration of natural uranium has decayed below the critical level. U235 has a half life of about 700 MY while U238 is 4500 MY so the ratio 235/238 must decrease over time. These reactor also occured at the bottom of lakes and rivers which supplied the moderator. They were also supposed to only have run intermitantly when conditions were ideal over a couple million years. They may have run for 100 years and then shut down for 25000 before starting again.

Mr Nuke is refering to the six factor formula for critcality and I agree I don't see how it could happen at the core. For one thing the 235 concentration has dropped there too. Density considerations might overcome that I don't know.

I have to figure out the quoting system here.

Originally posted by Agesilaus
The OKLO reactors only worked since the concentration of U-235 was high enough to permit a light water reactor to function. This was several billion years ago IIRC and since then the U235 concentration of natural uranium has decayed below the critical level. U235 has a half life of about 700 MY while U238 is 4500 MY so the ratio 235/238 must decrease over time. These reactor also occured at the bottom of lakes and rivers which supplied the moderator. They were also supposed to only have run intermitantly when conditions were ideal over a couple million years. They may have run for 100 years and then shut down for 25000 before starting again.

Mr Nuke is refering to the six factor formula for critcality and I agree I don't see how it could happen at the core. For one thing the 235 concentration has dropped there too. Density considerations might overcome that I don't know.

I have to figure out the quoting system here.

Finally someone who knows what I'm talking about!!! :D

To quote someone, use the hyperlinked 'quote' at the lower right of the post of the person you want to quote. It's standard vBulletin, just trimmed on graphics to save bandwith.

Sir, uranium has too short a half-life. We barely have any today for this reason.

Why nuclear radiation? There are simpler explanations.

Indeed, the amount of energy lost by the earth's surface is balanced by the energy it receives and produces -- an equilibrium. Much of the earth's internal energy is released through radioactive decay. When it's all considered, the amount of energy produced by spontaneous decay is pretty much exactly what's needed to explain the equilibrium we now enjoy. There's no need to invent a giant nuclear reactor.

- Warren

If we more appropriately assume that most heavy elements more or less mix proportionately at or near the center (due to the equal or almost equal effect of gravity originating from all sides)

This would not be the only force at work pushing towards a more equal mix. Convection must also be considered as a force to move the core material around.

On another note, Emfuser is proud of his newly earned BS in nuclear engineering. I don't blame him, I am sure he worked hard to get it.

Plainly there is now possible way the the earths core can be soild, this concept comes from little boys that play with rocks on the surface of the earth.
1.) universal attraction of the cosomos will not allow any body to be soild not even a rock, this is also know as the second law of thremal dynamics.
2.) it is well know that the llayers of earth must be seperated by relief or pressure or the earth would be a buring ball, this is record of tempture to depth ration, the event of a solid earth would result in temptures in excess of the suns surface.
3.) the event of a magnetic field also known as electromotive force, is one that is derived from focused energy, that exist in uniform, spartic eneryg dispersal results in sparatic and un unifed magnetic force, the event of uranium as a core simliy in themal emmision(spectrum emmision would be too hot to maintain a uniform magnetic field.
the earth has a hollow cors about 11 to 50 miles thick, surrounding this hollow core are helium and hydrogen about 137 miles thick, from there on out the denstiy of mass increases.
the event or barriers of the earth core after this magnetic field shell of helium and hydrogen are layers of rings that have points where ther is nothing at all but gases, or void, this layering barriere proccess are repeated over and over again until one reaches the surface.
in understanding the core of earth, hydrogen and helium are the only abundant elements in the universe, that have the energy freguency and coversion to feed the heat sink of the univsese 2degrees kelivn, the rest of the element that are know take to long to convert energy from the background constant of the universes or solar sysytmen, ther fgore they are just suck up by the endless spcae with the ablity to maintain a stable postion to congergate, this is why we have cosmic particles, and endless cloud bodies of hydrogen and helium in the universe, cosmic particle can con group and therfore are flying aroung hrdrogen and helium which can convert the background constants to feed its heat sink can group and therfore form clouds, these clouds are the beging of planets suns ect...,once these stable gases beging to form other element can find stblity near them and revolve aorund them. these heavy elements can not take the center of the hydrogen and helium mass as the are attracvted by the univese therfore thay float on the gases, as the mass grows and heats up heavy elements become more stable, however they can not take the center due to the event of unversal attraction, like wise hydrogen and helium can not tkae the center, this leave the center hollow with the gases revovling around the hollow, creating unifired motion such as rotation, ones mass forms a shell, the gaseous are and where polarized by the universe, this causes a magnetic field, and every planet has had one, or has one.
the reason that all bodies seen thorugh a telescope known as stars, suns, planets, are round is due to the event of universal attraction of the cosmos, called the background constant 2 degrees kelvin, as theis attracts on all side at all points the heavanly bodies are all round, and hollow, meaning that the attraction of the universe is so great that no object can have a soild center. not a even a atom.
DWAYNE D .L.RABON

universal attraction of the cosomos will not allow any body to be soild not even a rock, this is also know as the second law of thremal dynamics.

Hmmm... I thought the second law of thermodynamics says that the entropy of the universe increases. Silly me.

the event of a solid earth would result in temptures in excess of the suns surface

Therefore, all planets, moons, asteroids, etc., must be hollow.

the reason that all bodies seen thorugh a telescope known as stars, suns, planets, are round is due to the event of universal attraction of the cosmos, called the background constant 2 degrees kelvin, as theis attracts on all side at all points the heavanly bodies are all round, and hollow, meaning that the attraction of the universe is so great that no object can have a soild center. not a even a atom.



http://www.classicphotos.com/stooge/st-184.jpg

Uranium isn't exactly a trace element on the Earths surface. On the other hand it isn't abundant either. We should be asking ourselves why this is. Doesn't it seem logical to assume the heaviest Elements sank to the Earth's core during its early liquid state. It was nothing more than a smelting furnace back then and as most people will realise, heavy elements sink in a furnace.
Why do you think its hot downstairs? It's not friction or trapped heat from billions of years ago. That high temperature is trapped radioactive heat from the natural halflife of Uranium and other natural fissionable elements. Earth is a nuclear reactor and that heat has moved continents, created mountain ranges and generally shaped our world. Without it's violent upheavals the surface crust wouldn't have solidified with any heavy Elements in it at all. Including Gold and other dense metals. Natural reactors make life possible in this universe. The Sun is a reactor too as you all know. A massive fusion reactor. We should study nuclear technology to the fullest of our ability if only to better comprehend the natural universe around and below us.