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PurpleYouko
Member
Posts: 713
From: Columbia Missouri
Joined: 11-11-2004


(7)
Message 946 of 991 (709546)
10-28-2013 10:43 AM
Reply to: Message 940 by mindspawn
10-28-2013 7:28 AM


Re: This so bad it is disrespectful.
Hi Mindspawn.
I just had to get involved here as this thread has moved firmly into my area of expertise.
In case you are unfamiliar with my background, and you may well be as I don't post here very often, I am an analytical radio-chemist working in a research reactor.
The nuclear reactor that I work at was specifically built to test and answer questions such as the ones that you have been posting. It has a very tightly monitored and controllable neutron flux into which we deliberately place samples before actively measuring their decay rates.
One of the processes that we specialize in is called NAA (Neutron Activation Analysis) in which we irradiate a sample then measure the wavelengths of the prompt and delayed gamma rays that are always associated with radioactive decay.
So let's address a few of your points.

I feel that for an element to have a half-life of a few thousand years is still a slow process that can be affected by the current neutron background.

So you are suggesting that neutron flux can have an affect on the rate of decay correct?
It doesn't.
Samples decay at precisely the same rate whether they are left in the reactor core, left on a lab bench or completely surrounded by shielding. This has been tested quite extensively for more than 30 years here.
I do find myself wondering if you might be confusing something a little though.
It would make logical sense for neutron flux to slow down the decay process if the neutron capture path were identical but reversed to the decay path. Such a situation would indeed result in an equilibrium between neutron capture and decay.
However this is not the case.
The decay path is always different than the neutron capture path. To put it another way, the daughter isotope is always different than the original target isotope (the one that captured the neutron)

Let's take iron as an example as it has been mentioned a lot in this thread.
56Fe is the most common isotope at 91% of the total iron. It is also stable so it does not decay.
If 56Fe (thermal cross section 2.59) captures a neutron it becomes 57Fe which is also a stable isotope but which has a much lower natural abundance 2%
If 57Fe (thermal cross section 2.48) captures a neutron (it is slightly less likely to do so than 56Fe as it has a more tightly packed nucleus and therefore a slightly reduced Thermal cross section) it becomes 58Fe which is also stable.
if 58Fe (thermal cross section 1.28) it becomes 59Fe which is unstable and decays to 59Co with a half life of 44.5 days

Incidentally the reason that Boron shielding works to stop neutrons is because 10B has a thermal cross section of 3837 so a reasonably thick layer (couple of inches or so) is enough to capture any neutrons coming its way.
The Boron shields need to be replaced periodically though as capturing those neutrons results in an alpha particle and a 7Li atom

A good way to measure this would be to arrange two samples of the same consistency of parent/daughter, one shielded and one not. Measure the ratio, and then a few years later measure the ratio again. Depending on the half-life there should be a detectable difference between the two samples a few years later, the protected sample showing a higher proportion of daughter isotope than the unprotected sample.

That is actually a very well thought out experiment.
Scientists here thought that as well and tests such as this have been performed repeatedly at this and other reactors throughout the several decades of their existence.
The effects that you predicted were not discovered. the decay rates and hence the ratios, were found to be the same for all situations.

Iron is mainly stable, and when pushed into an unstable state (fe59 or fe60) it rapidly decays back to a stable state with days or within a few years. There are not enough neutrons in the neutron background to overcome the high decay rate and permanently change the iron.

OK two points here.
First of all as I have pointed out above, the effects of neutron flux on decay rates has been tested rather thoroughly and categorically ruled out as a possible way to change decay rates.
Secondly and much more seriously, the kind of thermal or fast neutron flux needed for any isotope to capture a neutron would be many orders of magnitude higher than any form of organic life could survive. Such a flux on the surface of the planet would inevitably result in a sterile radioactive wasteland.
This message is a reply to:
 Message 940 by mindspawn, posted 10-28-2013 7:28 AM mindspawn has responded

Replies to this message:
 Message 954 by mindspawn, posted 10-29-2013 7:25 AM PurpleYouko has responded

  
JonF
Member
Posts: 3410
Joined: 06-23-2003
Member Rating: 3.2


Message 947 of 991 (709568)
10-28-2013 12:14 PM


More evidence of no decay rate change
Not only do we have the non-correlation of 14C decay rates and magnetic field changes, here's a correlation between ice core layer counting and radiometric dating:

Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 kyr BP)

quote:
The Toba eruption that occurred some 74 kyr ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia where it constitutes a major time marker close to the Marine Isotope Stage 4/5 boundary. As yet, no tephra associated with Toba has been identified in Greenland or Antarctic ice cores. Based on new accurate dating of Toba tephra from Malaysia and on accurately dated European stalagmites the Toba event is known to occur between the onsets of Greenland Interstadials (GI) 19 and 20. Furthermore, the existing linking of Greenland and Antarctic ice cores by gas records and by the bipolar seesaw hypothesis suggests that the Antarctic counterpart is situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption based on matching of a pattern of bipolar volcanic spikes. Annual layer counting between volcanic spikes in both cores allows for a unique match. We first demonstrate this bipolar matching technique at the already synchronized Laschamp geomagnetic excursion (41 kyr BP) before we apply it to the suggested Toba interval. The Toba synchronization pattern covers some 2000 yr in GI-20 and AIM 19/20 and includes nine acidity peaks that are recognized in both ice cores. The suggested bipolar Toba synchronization has decadal precision. It thus allows a determination of the exact phasing of inter-hemispheric climate in a time interval of poorly constrained ice core records, and it allows for a discussion of the climatic impact of the Toba eruption in a global perspective. Furthermore, our bipolar match provides a way to place paleo-environmental records other than ice cores into a precise climatic context.

The Toba eruption has been dated to 75 kYa by Ar-Ar: A high-precision 40Ar/39Ar age for the Young Toba Tuff and dating of ultra-distal tephra: Forcing of Quaternary climate and implications for hominin occupation of India. Also by Electron Spin Resonance ESR dating of quartz phenocrysts in some rhyolitic extrusive rocks using Al and Ti impurity centres and U-Th disequilibrium Timescales of Magmatic Evolution by Coupling Core-to-rim 238U-230Th Ages and Chemical Compositions of Mineral Zoning in Allanite From the Youngest Toba Tuff

It's too bad that mindie's allergic to facts, data, and calculations.

Edited by JonF, : No reason given.


  
PaulK
Member
Posts: 12261
Joined: 01-10-2003
Member Rating: 2.6


Message 948 of 991 (709590)
10-28-2013 1:55 PM
Reply to: Message 937 by mindspawn
10-28-2013 5:52 AM


Re: Uniformity assumptions...
quote:

What is slowed is the amount of parent isotope that has decayed into daughter isotope. The rate of transformation from one to the other is slowed down. Our assumption of long timescales is based on currently measured rates of the proportions of parent to daughter isotope over short timeframes.

I see now what you're claiming. You assert that for all heavy elements neutron capture converts the atom into a heavier isotope which later decays into the original isotope. Which doesn't affect the actual decay rate.

There are obvious problems with this. First it isn't true. Second you haven't thought about the quantities your argument requires. Third you haven't even thought about how it would affect measurements of decay rates. Nor do you have any evidence that it is actually happening.

quote:

Yes it definitely depends on the elements. Most elements used in radiometric dating are heavy elements and have lengthy half-lives, and are more prone to neutron capture.

And the effects of neutron capture ALSO depend on the element and the isotope. for instance, neutron capture usually causes U235 to decay. Speeding up is not slowing down.. And changing the decay rate of the isotopes used in fission bombs and reactors by a large amount would have obvious - and catastrophic - consequences.

That is the sort of thing you need to take into account instead of assuming that all atoms of heavy elements behave in the same way.


This message is a reply to:
 Message 937 by mindspawn, posted 10-28-2013 5:52 AM mindspawn has not yet responded

    
NoNukes
Member
Posts: 9181
From: Central NC USA
Joined: 08-13-2010
Member Rating: 2.7


(1)
Message 949 of 991 (709636)
10-28-2013 9:11 PM
Reply to: Message 937 by mindspawn
10-28-2013 5:52 AM


Re: Uniformity assumptions...
What is slowed is the amount of parent isotope that has decayed into daughter isotope. The rate of transformation from one to the other is slowed down.

Let's explore the implications of this folly using U-238 as the example. U-238's half life is measured at 4.5 * 10^9 years or 1.4110^17 seconds. That half life is determined by detecting the rate of alpha emissions given off by a sample of U-238 as it decays by alpha decay to it's immediate daughter product Th 234. It is this process that you are claiming is slowed by neutrons.

Note however that slowing the process also slows the alpha emission rate. The alpha emission and the production of the daughter product result from the same cause.

Let's consider a 1 gram sample of U-238. Such a sample would contain about 3*10^21 atoms of U-238 (The atomic weight of U238 divided by Avagadros number). The decay of those atoms would be modeled by the following equation:

A = Ao * 1/2^(t/half life) where t is measured in the same units as the half life and Ao would be the initial number of atoms. We can find the decay rate by taking the derivative of the above equation.

dA/dT = 0.693*(Ao/half life)* 1/2^(t/half life).

Now let's consider the rate at the time the 1gram sample was purified and put on our lab bench. t =0.

dA/dT = 0.693 * 2 * 10^21 /1.41 * 10^17 * 1/2^0 = 10^4 decays per second.

That reflects what is actually observed for 1 gram of uranium 238 today.

But according to you, what I have calculated above is a depressed daughter production rate that is caused by a neutron flux. Note that rather than claiming that something caused a high rate back in the past, you claim that the current suppressed rate is caused by the presence of neutrons.

While you have not provided an exact number for the half life of old, you have suggested that it is as low as several thousand years. For convenience let's say 4500 years which also turns out to be 1 million times less than the current decay rate.

Performing the same calculation using a 4500 year half life suggests that the prehistoric rate of daughter production would have been 10^10 decays per second for the same 1 gram of U-238.

Back to the present.

So according to your ridiculous "theory" a neutron flux interacts with atoms of our 1 gram sample to prevent 10^10 - 10^4 decays every second. The difference is just 9.99999*10^9 decays/second daughters prevented. Forgive me if I refer to this difference as just 10^10 per second from now on.

So the neutron flux that strikes our 1 gram sample of U-238 must be on the order of 10^10 neutrons per second. The density of Uranium is about 19 g/cc, so this is the neutron flux that must enter 0.05 cubic centimeters every second.

In fact, 10^10 neutrons per second must be the neutron flux in every single 0.05 cubic centimeter place within our lab that we might choose to move our gram of U-238 or in which we might choose to put additional gram of U-238.

Okay, so what are the real numbers measured in the atmosphere? On the order of 10^6 neutrons per square cm. Completely insufficient for preventing 10^10 daughter products being made in a volume much smaller than a cm3.

I've simplified some things, but I don't believe I've made any simplifications that make things more difficult for you. I ignored the self shielding effect which would make the neutron flux less effective at reaching the inner parts of the sample. I also shrank the 1g sample by 50% when calculating the activity, so the number of decays prevented is too low by a factor of 1.5.

Any how, you wanted calculations. I doubt you'll find what you asked for all that useful, but here it is anyhow.

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I believe that a scientist looking at nonscientific problems is just as dumb as the next guy.
Richard P. Feynman

If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass


This message is a reply to:
 Message 937 by mindspawn, posted 10-28-2013 5:52 AM mindspawn has not yet responded

Replies to this message:
 Message 951 by Coyote, posted 10-28-2013 9:27 PM NoNukes has not yet responded
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 Message 956 by JonF, posted 10-29-2013 8:57 AM NoNukes has responded
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NoNukes
Member
Posts: 9181
From: Central NC USA
Joined: 08-13-2010
Member Rating: 2.7


Message 950 of 991 (709639)
10-28-2013 9:26 PM
Reply to: Message 937 by mindspawn
10-28-2013 5:52 AM


Re: Uniformity assumptions...
What is slowed is the amount of parent isotope that has decayed into daughter isotope. The rate of transformation from one to the other is slowed down. Our assumption of long timescales is based on currently measured rates of the proportions of parent to daughter isotope over short timeframes.

If we measured the amount of daughter products found in a sample of U238 and found there to be little to no daughter products, what age would we calculate for the sample?

I do not believe the answer is what you think it is.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

I believe that a scientist looking at nonscientific problems is just as dumb as the next guy.
Richard P. Feynman

If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass


This message is a reply to:
 Message 937 by mindspawn, posted 10-28-2013 5:52 AM mindspawn has not yet responded

Replies to this message:
 Message 953 by foreveryoung, posted 10-28-2013 10:37 PM NoNukes has not yet responded

    
Coyote
Member
Posts: 5529
Joined: 01-12-2008
Member Rating: 2.8


Message 951 of 991 (709640)
10-28-2013 9:27 PM
Reply to: Message 949 by NoNukes
10-28-2013 9:11 PM


Re: Uniformity assumptions...
Oh, noes! Math is hard! /Barbie /creationists

Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

Belief gets in the way of learning--Robert A. Heinlein

How can I possibly put a new idea into your heads, if I do not first remove your delusions?--Robert A. Heinlein

It's not what we don't know that hurts, it's what we know that ain't so--Will Rogers


This message is a reply to:
 Message 949 by NoNukes, posted 10-28-2013 9:11 PM NoNukes has not yet responded

  
JonF
Member
Posts: 3410
Joined: 06-23-2003
Member Rating: 3.2


Message 952 of 991 (709641)
10-28-2013 9:35 PM
Reply to: Message 949 by NoNukes
10-28-2013 9:11 PM


Re: Uniformity assumptions...
In Message 148 I came up with a speedup factor of 10^5. Even with that your point holds.

Any how, you wanted calculations.

You've now guaranteed he won't respond to your message.


This message is a reply to:
 Message 949 by NoNukes, posted 10-28-2013 9:11 PM NoNukes has not yet responded

  
foreveryoung
Member
Posts: 879
Joined: 12-26-2011


Message 953 of 991 (709644)
10-28-2013 10:37 PM
Reply to: Message 950 by NoNukes
10-28-2013 9:26 PM


Re: Uniformity assumptions...
That sounds like the following phrase from the princess bride: "I don't think that word means what you think it means".
This message is a reply to:
 Message 950 by NoNukes, posted 10-28-2013 9:26 PM NoNukes has not yet responded

    
mindspawn
Member
Posts: 1015
Joined: 10-22-2012


Message 954 of 991 (709647)
10-29-2013 7:25 AM
Reply to: Message 946 by PurpleYouko
10-28-2013 10:43 AM


Re: This so bad it is disrespectful.
So you are suggesting that neutron flux can have an affect on the rate of decay correct?
It doesn't.
Samples decay at precisely the same rate whether they are left in the reactor core, left on a lab bench or completely surrounded by shielding. This has been tested quite extensively for more than 30 years here.
I do find myself wondering if you might be confusing something a little though.
It would make logical sense for neutron flux to slow down the decay process if the neutron capture path were identical but reversed to the decay path. Such a situation would indeed result in an equilibrium between neutron capture and decay.
However this is not the case.
The decay path is always different than the neutron capture path. To put it another way, the daughter isotope is always different than the original target isotope (the one that captured the neutron)

Thanks for your informative reply, I accept what you say at face value.

The reason I came to the conclusion about the neutron flux is that recently Purdue University and the Geological Survey of Israel have noted the following four patterns in decay behavior which was always previously thought to be constant (I'm sure you are aware of the Purdue University studies, I will attach links if necessary):
1) Solar flares slow decay
2) Decay slows during July
3) Decay slows at midnight.
4) Decay slows according to the 11 year solar cycle
http://www.purdue.edu/...2010/100830FischbachJenkinsDec.html

These are the same behaviour patterns of muons, which show a stronger flux in all four of those conditions (I can supply links if required. Logically the July and midnight effect are largely caused by the tilt of the magnetic pole in winter, and the point of best penetration of the solar wind)

It was initially thought that neutrinos caused the fluctuating decay, but this possibility has largely been ruled out.

I noticed that muons had a matching pattern and also they caused neutrons in more than one manner, and neutrons would have logically had a direct effect through neutron capture , but as you say the decay path is different to the neutron capture path and the near equilibrium that I am proposing is not actually observed.

But the observation of a matching pattern between the two (muons and decay) shows that the penetration of the solar wind could be having a direct effect on decay. The strength of the magnetic field can strongly vary the penetration of the solar wind. Therefore the current assumption that decay has always been constant and the Purdue observations have only a minor effect on decay, is a little premature when we consider how directly a strong magnetic field has protected earth from the solar wind in the past. ie something in the solar wind (like proton induced muons) is having a current effect on decay, and that effect has the same pattern as particles that are sensitive to magnetic field fluctuations.

OK two points here.
First of all as I have pointed out above, the effects of neutron flux on decay rates has been tested rather thoroughly and categorically ruled out as a possible way to change decay rates.
Secondly and much more seriously, the kind of thermal or fast neutron flux needed for any isotope to capture a neutron would be many orders of magnitude higher than any form of organic life could survive. Such a flux on the surface of the planet would inevitably result in a sterile radioactive wasteland

Ok I accept your first point, must still look into your second point.

Edited by mindspawn, : No reason given.


This message is a reply to:
 Message 946 by PurpleYouko, posted 10-28-2013 10:43 AM PurpleYouko has responded

Replies to this message:
 Message 955 by JonF, posted 10-29-2013 8:07 AM mindspawn has not yet responded
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JonF
Member
Posts: 3410
Joined: 06-23-2003
Member Rating: 3.2


Message 955 of 991 (709648)
10-29-2013 8:07 AM
Reply to: Message 954 by mindspawn
10-29-2013 7:25 AM


Still scared to death of calculations anfd data
Still scared to death of calculations and data. Pathetic.

The studies to which you refer are quite controversial, preliminary, and not generally accepted.

Whereas your fantasy has been conclusively falsified in many ways, although you can't bring yourself to accept it.

French fried people.

Edited by JonF, : No reason given.


This message is a reply to:
 Message 954 by mindspawn, posted 10-29-2013 7:25 AM mindspawn has not yet responded

  
JonF
Member
Posts: 3410
Joined: 06-23-2003
Member Rating: 3.2


Message 956 of 991 (709652)
10-29-2013 8:57 AM
Reply to: Message 949 by NoNukes
10-28-2013 9:11 PM


Re: Uniformity assumptions...
Oh, I just noticed this:

While you have not provided an exact number for the half life of old, you have suggested that it is as low as several thousand years. For convenience let's say 4500 years which also turns out to be 1 million times less than the current decay rate.

Betcha mean current half-life

So the neutron flux that strikes our 1 gram sample of U-238 must be on the order of 10^10 neutrons per second

Isn't that a way-low lower bound? I bet nobody knows the cross-section for the alleged reaction, in principle there would be one.

Edited by JonF, : No reason given.

Edited by JonF, : No reason given.


This message is a reply to:
 Message 949 by NoNukes, posted 10-28-2013 9:11 PM NoNukes has responded

Replies to this message:
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PurpleYouko
Member
Posts: 713
From: Columbia Missouri
Joined: 11-11-2004


Message 957 of 991 (709675)
10-29-2013 11:13 AM
Reply to: Message 954 by mindspawn
10-29-2013 7:25 AM


Re: This so bad it is disrespectful.
Thanks for your informative reply, I accept what you say at face value.

Thanks for that.
I could probably dig up all kinds of references if pushed but they would all be pretty old now. This question was considered to be fully resolved many many decades ago. It might be kind of hard to find papers online now.

I was aware of some data from Purdue and Stanford, as well as several others, that show a very tiny (fractions of a percent) cyclic fluctuations but until now I hadn't really read about it in detail.
It's actually extremely interesting reading and surprisingly well accepted in the scientific community. I half expected to find papers that challenge the initial findings but on the whole, every team of researchers that have repeated the same experiments, with and without modifications, have come up with pretty much the same results.
The decay rates of whatever isotope is being studied appears to slow down very slightly in response to increased activity in the sun. It has even been successfully used to measure the effect 2 days before a solar flare.

However there is still a question of what the actual cause of the effect really is. It was initially thought to be neutrino flux but it is still quite possible that some unknown particle is responsible.

Some experiments have been carried out in order to determine if neutrino flux is indeed the culprit
http://arxiv.org/pdf/1006.5071v1.pdf
their conclusion was not entirely conclusive though
They experimentally took two radioactive samples and made them into two different shapes (flat sheet and sphere). In the sphere, the neutrino flux produced by the decay of the sample itself was many times greater than the solar Neutrino flux while in the flat sheet it was negligable. They did indeed note a small change between the two but it was so small that more experiments are needed to confirm the hypothesis.

quote:
Our results in Table 1 indicate a ~2.3 sigma deviation of the foil/sphere ratio in experiment 1 from unity.
From Table 2, based on the initial 30 spectra, the foil/sphere ratio for experiment 2 deviates from unity by ~2.6 sigma.
These results thus leave open the possibility that the half-life of a radioactive nu-clide could in fact depend on its shape (due to the internal flux of neutrinos, photons, or electrons)

So yes there does seem to be a measurable change in the decay rates due to something going on in the sun.
But what effect does slowing the decay rate by a fraction of 1 percent for short periods of time during increased solar activity have on radiometric dating?

First, initial decay rates were probably (I'm not sure about this) measured over a relatively long period, say a few months, due to the inacuracies of the timers that were available back in the day. If this is true then those rates would have been an average. No?

Second. If there had been much greater activity in the sun in times past then the dates as we measure them today would be incorrect (by 0.1%) in the direction of the measurements being too short.

Third. A difference of 0.1% in the measurements would be lost in the experimental noise of most dating methods. In any analytical process it is typical to have a standard deviation of up to 0.5% around the mean value. ) 0.2% is considered to be almost perfect.
I will grant you though, isotope ration measurements need to be a bit better than that, typically in the order of 0.05% or better but that is just in the actual ratio measurement and not in the resulting calculations related to sample age. The potential error bars there are well in excess of 0.1% so as i said this error would be lost in the noise.

Ok I accept your first point, must still look into your second point.

It's possible that I misspoke just a little bit. It's a difficult subject to research apparently.
Here is some stuff that I've been able to find on the subject.

We should be able to work out the actual neutron flux at sea level easily enough

first of all here is the measured average dose for the USA measured in mili-rems
http://web.mit.edu/newsoffice/1994/safe-0105.html

quote:
The average exposure in the United States, from natural sources of radiation (mostly cosmic radiation and radon), is 300 millirems per year at sea level. Radiation exposure is slightly higher at higher elevations-thus the exposure in Denver averages 400 millirems per year.

Here is a table showing the relative conversion factor from neutron flux to mili-rems http://miscpartsmanuals3.tpub.com/...5-315/TM-55-3150014.htm
I can't get the stupid table to display properly in this post because it seems to be in pdf form so here is a summary of the information.
The lowest energy neutron (thermal) flux when measured in neutrons per square centimeter per second is compared to mili-rems per hour in the following proportions

268.0 neutrons/square centimeter/second == 1 mili-rem per hour (note this is measured as a whole body dose)
if the average whole body dose from background radiation in the USA is 300 mili-rem then we need to divide that 268.0 by the number of hours in a year (8760 assuming exactly 365 days)

therefore the average neutron flux (assuming only thermal neutrons exist)
268 / 8760 = 0.0306 neutrons/square centimeter/second or about 1 neutron every 30 seconds or so.
In actual fact there are quite a large proportion of neutrons that are higher energy so the total flux would be significantly less than that.

The whole body dose that is considered to be borderline 'safe' is about 50,000 mili-rems per year. That is 166 times greater than the basic flux at sea level so that means that a flux of 5.1 neutrons/square cm/second would be approaching the upper limits of survivability. Any more than that and we would require shielding to survive.

I'm not going to take the math any further than that for now.
The only point that I would like to make here is that such a low neutron flux is not likely to activate very many atomic nuclei in a given sample. Sure over a large area it is eventually going to be lethal to most life forms but to a chunk of iron, one cm cubed, there will not be very many activations if you get my meaning. most neutrons will pass straight through solid matter.


This message is a reply to:
 Message 954 by mindspawn, posted 10-29-2013 7:25 AM mindspawn has responded

Replies to this message:
 Message 964 by mindspawn, posted 10-30-2013 7:29 AM PurpleYouko has responded

  
PurpleYouko
Member
Posts: 713
From: Columbia Missouri
Joined: 11-11-2004


Message 958 of 991 (709677)
10-29-2013 11:32 AM
Reply to: Message 949 by NoNukes
10-28-2013 9:11 PM


Re: Uniformity assumptions...
Okay, so what are the real numbers measured in the atmosphere? On the order of 10^6 neutrons per square cm.

Can you tell me where you got this figure from.
My research leads me to a conclusion that the true value at sea level is closer to 0.05 neutrons/square cm/second or even less.
http://www.lanl.gov/science/NSS/issue1_2012/story4full.shtml
quote:
These neutrons, like ghosts, can pass through materials without being noticed. At aircraft cruising altitudes, about 2,000 of them per second penetrate each square yard of the aircraft's surface, passing through the passengers, seats, and onboard electronics and exiting on the other side.

that works out at about 0.2 neutrons/cm squared/second at 30,000 feet above sea level.

Or is your claimed flux not expressed per second?
I notice that there is no time component listed in your post.
The figure above (0.2/sec) when calculated out to neutrons/square cm/year is indeed around 6 million. 6,307,200 to be exact


This message is a reply to:
 Message 949 by NoNukes, posted 10-28-2013 9:11 PM NoNukes has responded

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 Message 959 by JonF, posted 10-29-2013 1:30 PM PurpleYouko has not yet responded
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JonF
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Posts: 3410
Joined: 06-23-2003
Member Rating: 3.2


Message 959 of 991 (709722)
10-29-2013 1:30 PM
Reply to: Message 958 by PurpleYouko
10-29-2013 11:32 AM


Re: Uniformity assumptions...
It seems you're in the right ballpark: Terrestrial thermal neutrons:

quote:
The first NIST-traceable measurements of environmental thermal neutrons have been completed. The average sea level flux of thermal neutrons is 4 cm^2/hr.

Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (1966), annex A, page numbered 17:

quote:
Kastner et al.60 using a liquid scintillator. reported a flux density of 4.5 X 10^-3 n/cm^2 X second for neutrons with energies from 1 to 10 MeV as measured directly at an altitude of 180 metres. They suggested a total neutron flux density at sea level ( 41 N) of about 10^-2 n/;cm^2 X second, 15-25 per cent of which are in the energy range 1 to 10 MeV, and about 70 per cent have lower energies.

It seems reasonable to follow the suggestion of Kastner et al.60 and to assume the value of 10^-2 n/cm^2 X second as the total neutron flux density at sea level. A lower value of 0.54 X 10^-2 n/cm^2 X second at sea level as given by Haynes,58 was recently used as a basis for dose estimates. 61



This message is a reply to:
 Message 958 by PurpleYouko, posted 10-29-2013 11:32 AM PurpleYouko has not yet responded

  
PaulK
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Posts: 12261
Joined: 01-10-2003
Member Rating: 2.6


Message 960 of 991 (709732)
10-29-2013 2:34 PM
Reply to: Message 954 by mindspawn
10-29-2013 7:25 AM


Re: This so bad it is disrespectful.
quote:

The reason I came to the conclusion about the neutron flux is that recently Purdue University and the Geological Survey of Israel have noted the following four patterns in decay behavior which was always previously thought to be constant (I'm sure you are aware of the Purdue University studies, I will attach links if necessary):
1) Solar flares slow decay
2) Decay slows during July
3) Decay slows at midnight.
4) Decay slows according to the 11 year solar cycle
http://www.purdue.edu/...2010/100830FischbachJenkinsDec.html

Let us note that all these changes are tiny. The change that you need is massive. THat's why you need numbers.

quote:

These are the same behaviour patterns of muons, which show a stronger flux in all four of those conditions (I can supply links if required. Logically the July and midnight effect are largely caused by the tilt of the magnetic pole in winter, and the point of best penetration of the solar wind)

Let us note that you are speculating here. THe same would apply to any charged particle.

quote:

I noticed that muons had a matching pattern and also they caused neutrons in more than one manner, and neutrons would have logically had a direct effect through neutron capture , but as you say the decay path is different to the neutron capture path and the near equilibrium that I am proposing is not actually observed.

There doesn't seem to be anything logical about it. It's piling speculation on speculation with no attempt to check the truth of those speculations. To rationally conclude that neutron flux caused any significant reduction in decay rates, one would have to investigate the consequences of neutron capture to see if the mechanism is plausible, and work out the effect that this mechanism would have on real measurements of decay rate. And that's still a long way from having anything that would amount to a serious challenge to radiometric dating.

quote:

Therefore the current assumption that decay has always been constant and the Purdue observations have only a minor effect on decay, is a little premature when we consider how directly a strong magnetic field has protected earth from the solar wind in the past. ie something in the solar wind (like proton induced muons) is having a current effect on decay, and that effect has the same pattern as particles that are sensitive to magnetic field fluctuations.

The irony of it! In fact the conclusion that the effect is minor is far better supported than your view that neutrons are responsible. We have the opinion of the researchers and we have the consilience of different methods to point to two. That is rather better than speculations made in ignorance of the facts.

So, why do you place such great faith in your idle speculations ?

And answer to this could do much to illuminate the mindset of the creationists.

Edited by PaulK, : No reason given.


This message is a reply to:
 Message 954 by mindspawn, posted 10-29-2013 7:25 AM mindspawn has not yet responded

    
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