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Dude
SFN Die Hard
USA
6891 Posts |
 Posted - 05/10/2011 : 14:38:11 [Permalink]
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Originally posted by Dr. Mabuse
Originally posted by Dude
Just to add... Uranium 235 and 233 both decay into different isotopes of Thorium, and no isotope of Thorium has a critical mass. Doesn't go boom. |
My point is that quantum mechanical constants that control decay also affects which configurations of atomic nucleus might spontaneously undergo fission, and what end products you get from it. With changed constants, spontaneous fission of Thorium, or U238 might happen, just as well as the possibility of U238 possibly becoming stable. The different critical masses of various elements would change, in some cases drastically.
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I really don't know much about QM. What constants are we talking about that, if changed, could change what elements and isotopes even have a critical mass?
The way I understand it now, only if Uranium could somehow turn into Plutonium via decay could you get the scenario you initially described, spontaneous critical mass. That would mean that entropy could spontaneously run in reverse, that things don't trend toward lower energy. Seems like that would have implications for the very existence of the universe, among other things.
I still don't see how decay rates speeding up, or even being wildly variable, could make that happen. But like I said, I don't really know much about QM, not my field!
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
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Ebone4rock
SFN Regular
USA
894 Posts |
Posted - 05/10/2011 : 14:39:18 [Permalink]
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| I love it when you guys talk all sciencey. I don't understand a word of it but for some reason it makes me feel real smart! |
Haole with heart, thats all I'll ever be. I'm not a part of the North Shore society. Stuck on the shoulder, that's where you'll find me. Digging for scraps with the kooks in line. -Offspring |
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On fire for Christ
SFN Regular
Norway
1273 Posts |
Posted - 05/10/2011 : 15:19:18 [Permalink]
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My point is that quantum mechanical constants that control decay also affects which configurations of atomic nucleus might spontaneously undergo fission, and what end products you get from it. With changed constants, spontaneous fission of Thorium, or U238 might happen, just as well as the possibility of U238 possibly becoming stable. The different critical masses of various elements would change, in some cases drastically.
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Good job typing that before your keyboard exploded. |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/10/2011 : 15:56:24 [Permalink]
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Originally posted by Dude
I really don't know much about QM. What constants are we talking about that, if changed, could change what elements and isotopes even have a critical mass? |
I'm not really a physicist either, but I did take some classes on college level.
Spontaneuous fission is a specific kind of nuclear decay in large nucleus. Nuclear decay depends on the Weak Nuclear force, and its relation to the strong nuclear force. It's obvious to me at least that a change in the domain in which the weak force acts will affect the strong force's ability to contain the nucleus. Is the specific name of the constant important? I don't know enough QM to pin it on a specific constant, but suppose the Gluon didn't carry as much energy as it does. Just as an example.
This isn't a new idea, it's been circling around as long as YECists have posited that the speed of light could have been faster 6010 years ago when god created the universe.
The way I understand it now, only if Uranium could somehow turn into Plutonium via decay could you get the scenario you initially described, spontaneous critical mass.
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...or if the threshold for spontaneous fission suddenly lowered because of the change in QM-constants that regulates the balance in the atomic nucleus.
Since "regular" decay and spontaneous fission both depends on the weak nuclear force, it's logical that something that affected the first would also affect the second.
But then, what in QM is truly logical?
Damn, where's Boron10 when you need him...
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Dude
SFN Die Hard
USA
6891 Posts |
Posted - 05/11/2011 : 09:52:13 [Permalink]
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Decay involves the strong and weak forces, and electrostatic force as well. If the strength of those forces change enough to effect decay rates enough to allow a 6000 year old universe, I am pretty sure atomic nuclei would not be able to hold together at all. Atoms and elements couldn't exist.
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Ignorance is preferable to error; and he is less remote from the truth who believes nothing, than he who believes what is wrong.
-- Thomas Jefferson
"god :: the last refuge of a man with no answers and no argument." - G. Carlin
Hope, n.
The handmaiden of desperation; the opiate of despair; the illegible signpost on the road to perdition. ~~ da filth |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/11/2011 : 13:41:10 [Permalink]
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| Even small changes in the forces' constant will have serious effects on the world as we know it. |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 05/11/2011 : 15:05:40 [Permalink]
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Nuclear chain-reactions (that drive A-bombs and power generation) don't depend upon spontaneous decay. It's a chain reaction, after all. One atom decays, and the neutrons whack into other Uranium atoms which then decay, etc. Increasing the spontaneous decay rate of Uranium will not lead to smaller critical masses.
It would, however, increase the amount of heat generated by spontaneous decay. If decay rates were so much higher in the past that 4-billion-year isotope decay ages were actually from 6,000 years ago, the Earth would still be molten from the heat of radioactivity alone.
On a related note, check out the Oklo natural nuclear fission reactors:Oklo is the only known location for this in the world and consists of 16 sites at which self-sustaining nuclear fission reactions took place approximately 2 billion years ago, and ran for a few hundred thousand years, averaging 100 kW of power output during that time. |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/11/2011 : 15:51:25 [Permalink]
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Originally posted by Dave W.
Nuclear chain-reactions (that drive A-bombs and power generation) don't depend upon spontaneous decay. It's a chain reaction, after all. |
True, but an increased number of spontaneous fissions will increase the number of available neutrons (and could also potentially increase the number of neutrons from each single fission), and the nucleus would become more unstable making them split rather than just absorb a neutron hitting it.
It is the scarcity of spontaneous fissions (and released neutrons from that fission) that sets the critical mass limit, where neutrons are rare enough to not set off a chain reaction.
A sphere of fissible material designed to be sub-critical with a 5kg critical mass limit in mind could become critical if the critical mass limit suddenly dropped to 3kg.
In the same way, U238 which is stable enough to be used in nuclear power plants, could get more susceptible to spontaneous fission (and would rather split than just absorb a neutron hitting it). Suddenly a nuclear power plant would be loaded with potentially weapons-grade uranium and go boom...
| One atom decays, and the neutrons whack into other Uranium atoms which then decay, etc. Increasing the spontaneous decay rate of Uranium will not lead to smaller critical masses. |
But the decay rate doesn't exist in a "vacuum". Tweaking a fundamental constant of nature to increase the decay rate will upset a lot of other dependencies. That's my point. Uranium producing more heat is a minor effect, in the grand scheme of things. But of course as you write, this minor effect is great enough to keep Earth being an ocean of molten rock.
On a related note, check out the Oklo natural nuclear fission reactors:Oklo is the only known location for this in the world and consists of 16 sites at which self-sustaining nuclear fission reactions took place approximately 2 billion years ago, and ran for a few hundred thousand years, averaging 100 kW of power output during that time.
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I was thinking of that place yesterday. Nature is grand in all its awesomeness, isn't it? 
(edited for clarification) |
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| Edited by - Dr. Mabuse on 05/11/2011 16:08:15 |
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Dave W.
Info Junkie
USA
26022 Posts |
Posted - 05/11/2011 : 18:04:46 [Permalink]
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Originally posted by Dr. Mabuse
True, but an increased number of spontaneous fissions will increase the number of available neutrons (and could also potentially increase the number of neutrons from each single fission), and the nucleus would become more unstable making them split rather than just absorb a neutron hitting it.
It is the scarcity of spontaneous fissions (and released neutrons from that fission) that sets the critical mass limit, where neutrons are rare enough to not set off a chain reaction.
A sphere of fissible material designed to be sub-critical with a 5kg critical mass limit in mind could become critical if the critical mass limit suddenly dropped to 3kg.
In the same way, U238 which is stable enough to be used in nuclear power plants, could get more susceptible to spontaneous fission (and would rather split than just absorb a neutron hitting it). Suddenly a nuclear power plant would be loaded with potentially weapons-grade uranium and go boom... |
But how often atoms of a material spontaneously decay isn't a factor in determining critical mass. In fact, since raising the temperature increases the critical mass limit, increasing the spontaneous fission rate could work negatively against a self-sustaining reaction.
Look at the data Wikipedia gives (for ease of comparison, when ranges were given for critical mass, I took the average... I also rounded all the numbers):
Isotope | Crit. Mass | Half-life
----------------+------------+------------
proactinium-231 | 750 | 32,760
uranium-233 | 15 | 160,000
uranium-235 | 52 | 703,800,000
neptunium-236 | 7 | 154,000
neptunium-237 | 60 | 2,144,000
plutonium-238 | 10 | 88
plutonium-239 | 10 | 24,200
plutonium-240 | 40 | 6,563
plutonium-241 | 12 | 14
plutonium-242 | 88 | 373,300
americium-241 | 66 | 432
americium-242m | 12 | 141
americium-243 | 230 | 7,370
curium-243 | 9 | 29
curium-244 | 22 | 18
curium-245 | 11 | 8,500
curium-246 | 55 | 4,730
curium-247 | 7 | 15,600,000
californium-249 | 6 | 351
californium-251 | 5 | 898
----------------+------------+------------
I don't see a whole lot of correlation between short half-lives and small critical masses up there.
Of course, as you note with your talk of dependencies, there are a lot of other factors involved. But nobody seems to be talking about a high rate of spontaneous fissioning to be a benefit to either nuclear bombs or power reactors.
(Edited to fix some numbers.) |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 05/11/2011 : 19:42:10 [Permalink]
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Originally posted by Dave W.
Of course, as you note with your talk of dependencies, there are a lot of other factors involved. But nobody seems to be talking about a high rate of spontaneous fissioning to be a benefit to either nuclear bombs or power reactors.
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Not as a benefit as such. But as in setting a device off prematurely.
A theoretical 100% pure Pu-239 weapon could also be constructed as a gun-type weapon, like the Manhattan Project's proposed Thin Man design. In reality, this is impractical because even "weapons grade" Pu-239 is contaminated with a small amount of Pu-240, which has a strong propensity toward spontaneous fission. Because of this, a reasonably-sized gun-type weapon would suffer nuclear reaction before the masses of plutonium would be in a position for a full-fledged explosion to occur. Emphasis above mine.
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Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
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Tim Thompson
New Member
USA
36 Posts |
Posted - 09/07/2011 : 16:11:17 [Permalink]
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Originally posted by the_ignored
You just know that outfits like AIG will be all over this one.
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They shouldn't give all the credit to the guys from Stanford. Claims for time variability of radioactive decay rates goes back at least to 2001. Since then Russian researchers have claimed annual variability of beta decay rates on the order of 0.2%. But the Stanford guys are from Stanford, not Russia, so naturally they get all the press. Still, they may be the first ones to associate the variability with solar cycles. They also find the same order of magnitude change in decay rates, 0.2% to 0.3%. There are a couple of groups who dispute that result and see no sign of variability in their data.
Meanwhile, it has already been established that the electron capture decay of 7Be can vary by as much as 0.4% under pressure or depending on implanting into a solid state environment. This is because the inner electron shell for 7Be is close enough to the nucleus to alter the wave-function overlap with the nucleus. 40K, which is used in radiometric dating, also decays by electron capture, but there has been no indication of a similar variability with it. No surprise, since the 40K inner electron is shielded by so many outer electrons that you can't deform the wave-function so easily.
If true, and some of these claims certainly are, note that all of the variability of decay rates is significantly less than 1%. Furthermore, I am unaware of any such claims associated with isotopes used in radiometric dating. However, even if there were such claims, the ages derived are linear with respect to the decay rate, so a variation of less than 1% in decay rate will translate into a variability of less than 1% in the derived age, which I suspect is smaller than the random noise already associated with such ages.
So creationists have a lot of work to do if they try to run with results like these. |
The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell |
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bngbuck
SFN Addict
USA
2437 Posts |
Posted - 09/07/2011 : 23:41:31 [Permalink]
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Fascinating dialog! Learned more about paticle physics in ten minutes than I could in a semester of Freshman Physics 101.
Knowing less than nothing about the subject, I'm going with Tim whose declarations just sound so.......I don't know,... professional!
Tim, do you work in, or teach, particle physics or perhaps chemistry? I could use a tutor. And welcome to SFN. Expertise in any area is certainly welcome here! |
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Dr. Mabuse
Septic Fiend
Sweden
9688 Posts |
Posted - 09/08/2011 : 06:48:41 [Permalink]
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Hello Tim and welcome to Skeptic Friends Network.
And thanks for the information. Especially about how the decay-rate of beryllium can change under pressure. Overlapping wave-functions never crossed my mind. |
Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3
"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse
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Tim Thompson
New Member
USA
36 Posts |
Posted - 09/08/2011 : 08:41:33 [Permalink]
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Originally posted by bngbuck
Tim, do you work in, or teach, particle physics or perhaps chemistry?
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I am retired from the technical staff at the Jet Propulsion Laboratory. My M.S. is in physics; most of my experience is in atmospheric physics (mostly radiative transfer) and science data & image analysis, in astronomy, astrophysics, and geological infrared remote sensing. |
The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell |
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Decay rates changing?
