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Radioactive Decay Rates


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#41 NewPath

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Posted 19 September 2012 - 01:19 AM

Lots of things 'could' happen. 'Could' doesn't mean 'should be taken seriously'. If you look at the Fishbach paper you'll see that the decay counts actually increased (look at the slope) after the more powerful X-class flares. You'd need to think that a weaker flare produced a lot of muons while a much stronger flare produced fewer/none. That's a bit problematic since you've already argued that the X-class flare produced a increase in muons at ground level.

For approximately every 70 C class flares that precede an x-class flare, you should have a muon spike. It can happen, its rare, and that's the case with the Purdue data. No further data has proved any definite pattern of a 40 hour spike before every X-class flare so everything is consistent with a rare event. I am sure you agree with me that this spike in decay is rare, as is a C-class flare producing high speed protons.

Just the low pressure system over Indiana was enough to cause a muon spike that day.Which makes our whole c-class flare discussion irrelevant, conditions were perfect for a muon spike when they recorded that decay slowdown.

With a change in decay rate after 1 day of only 10%: The amount of Pu lost in the previous 1 day would be 9.1*10^20 atoms. The thermal output of the leftover at the new accelerated decay rate would be 14500 W. That's a 10% increase from the launch value. There was no spike in power above the launch value so we can rule out any large change in decay rates from your idea.

Muons are normally created 5 km in the air, a rocket travelling at 250 km per hour would pass through the muon region in just over one minute, this 1 minute period would not even show on a graph that depicts an entire two year period. I would like to see data from that first one minute. The decay should decrease rapidly for that one minute, followed by a sharp rise, undecayed muons peaking close to the 5km mark.

The earth is overwhelmingly made up of non-radioactive isotopes. Just considering available targets a incoming particle is more likely to strike a non-radioactive atom than a radioactive one. As an example, the most common isotope (90%) of the most common element on earth (32%) is Iron-56. If a muon was able to strike Fe-56 and convert a proton into a neutron (remember charge needs to be conserved so a negatively charged muon can't create a neutron unless it cancels out a positive charge) it would result in MN-56 which is unstable. The number of radioactive decays would increase not decrease because a non-radioactive element was converted into a radioactive element.


i thought we were referring to a laboratory containing already radioactive elements. I am still trying to work out how the gamma radiation dropped there.


.

Also if you want to use muons as a source for adding neutrons to individual atoms, you should look up the relative abundance of incoming muons vs the number of atoms in a mole. The average influx of muons at sea level is around 1 per minute per cm^2. You linked to a paper showing a 100% increase in muons during a flare, but getting 2 muons instead of 1 per minute isn't going to do much. If you had 10 muons per cm^2 per minute and each one struck a different atom in a 1cm cube of Mn-54, it would take 15,000,000,000,000,000 years to strike all of them. It would require 15 trillion years just to affect .1% of the atoms.
http://cosmic.lbl.go..._Rays/Muons.htm


I am more referring to the dispersion of many neutrons during that muon bombardment, than the muons themselves having an effect. The full effects of muon spallation on the production of neutrons is not known:

https://e-reports-ex.../pdf/340911.pdf

Neutron production due to cosmic muon spallation is a constant source of background for long-dwell measurements of fissionable material. As such, it is important to understand the different underlying physical processes that contribute to neutron production via muon spallation, and their accompanying systematics. Due to the complicated interactions that lead to secondary neutrons, however, a well established theory describing this phenomena is not known.

#42 miles

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Posted 19 September 2012 - 04:52 PM

For approximately every 70 C class flares that precede an x-class flare, you should have a muon spike. It can happen, its rare, and that's the case with the Purdue data. No further data has proved any definite pattern of a 40 hour spike before every X-class flare so everything is consistent with a rare event. I am sure you agree with me that this spike in decay is rare, as is a C-class flare producing high speed protons.

Just the low pressure system over Indiana was enough to cause a muon spike that day.Which makes our whole c-class flare discussion irrelevant, conditions were perfect for a muon spike when they recorded that decay slowdown.

Muons are normally created 5 km in the air, a rocket travelling at 250 km per hour would pass through the muon region in just over one minute, this 1 minute period would not even show on a graph that depicts an entire two year period. I would like to see data from that first one minute. The decay should decrease rapidly for that one minute, followed by a sharp rise, undecayed muons peaking close to the 5km mark.

I think you missed the point. The power on the ground was around 880W from 13000W of thermal energy. No matter when you want the transition point to be (1 minute, 1 day, 1 year...) if the decay rate increases the electrical energy will increase by a similar percentage. If the half life got 10% faster 1 minute after launch the thermal energy would be around 14300W and the electrical energy should increase to over 900W at the very least, and most likely be around 970W. A 10% faster decay rate in space would cause the energy produced in space to stay above the ground power rate of 880W for years. The data shows that didn't happen at all.

There are 3 of these on the Cassinni probe
http://en.wikipedia.org/wiki/GPHS-RTG
"Each GPHS-RTG has a mass of about 57 kg and generates about 300 Watts of electrical power at the start of mission (5.2 We/Kg), using about 7.8 kg of Pu-238 based fuel which produces about 4,400 Watts of thermal energy"
Just to show that the ~13000W thermal, 878W electrical values are from earth measurements, my last post calculated the expected thermal energy from a standard earth-measured 87.7 year half life and came up with around 13100 which matches nicely with the ~4400 x 3 thermal expectation and the 878W at launch value is consistent with the ~300x3 electrical power spec for the devices.

i thought we were referring to a laboratory containing already radioactive elements. I am still trying to work out how the gamma radiation dropped there.

If you want an effect to change dates on samples taken from nature you need to account for the fact that most of nature is made up of non-radioactive elements so most muon interaction will be affecting non-radioactive elements.

I am more referring to the dispersion of many neutrons during that muon bombardment, than the muons themselves having an effect. The full effects of muon spallation on the production of neutrons is not known:

https://e-reports-ex.../pdf/340911.pdf

Neutron production due to cosmic muon spallation is a constant source of background for long-dwell measurements of fissionable material. As such, it is important to understand the different underlying physical processes that contribute to neutron production via muon spallation, and their accompanying systematics. Due to the complicated interactions that lead to secondary neutrons, however, a well established theory describing this phenomena is not known.


Having a comprehensive theory about an effect is not necessary to simply measure an effect. The effect you are talking about is both very small and acts to remove neutrons from nuclei, not add them as you previously suggested with your (Mn-54 to Mn-55 idea). Not all free neutrons get captured so that's an additional hurdle to overcome.

http://ilias.in2p3.f...7/L_Pandola.pdf
Typical flux of fast muon-induced neutrons in deep underground Labs (LNGS, Boulby) ≈ 10-9 cm-2s-1 (> 1 MeV) 1000 times smaller than neutrons from rock radioactivity.

That's .000000001 neutrons per sq centimeter per second. Remember what I showed you about needing 15 trillion years to affect .1% of atoms in a square cm with .6 muons per second. The same issue applies here except neutrons from muons are much less common than muons so the time would be even longer.

#43 NewPath

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Posted 19 September 2012 - 11:29 PM

I think you missed the point. The power on the ground was around 880W from 13000W of thermal energy. No matter when you want the transition point to be (1 minute, 1 day, 1 year...) if the decay rate increases the electrical energy will increase by a similar percentage. If the half life got 10% faster 1 minute after launch the thermal energy would be around 14300W and the electrical energy should increase to over 900W at the very least, and most likely be around 970W. A 10% faster decay rate in space would cause the energy produced in space to stay above the ground power rate of 880W for years. The data shows that didn't happen at all.

There are 3 of these on the Cassinni probe
http://en.wikipedia.org/wiki/GPHS-RTG
"Each GPHS-RTG has a mass of about 57 kg and generates about 300 Watts of electrical power at the start of mission (5.2 We/Kg), using about 7.8 kg of Pu-238 based fuel which produces about 4,400 Watts of thermal energy"
Just to show that the ~13000W thermal, 878W electrical values are from earth measurements, my last post calculated the expected thermal energy from a standard earth-measured 87.7 year half life and came up with around 13100 which matches nicely with the ~4400 x 3 thermal expectation and the 878W at launch value is consistent with the ~300x3 electrical power spec for the devices.


this is all very approximate. "About 300 watts" "around 880 watts". Even the 10% we are expecting is approximate, it was some scientists thumb suck that you quoted, maybe 5% is more accurate. The approximate starting energy compared to the subsequent 2 year graph just is not giving out enough information. We need second by second information during the first 3 minutes to get a good handle on this, otherwise we are wasting our time using approximate figures to try and find a small percentage difference.

Having a comprehensive theory about an effect is not necessary to simply measure an effect. The effect you are talking about is both very small and acts to remove neutrons from nuclei, not add them as you previously suggested with your (Mn-54 to Mn-55 idea). Not all free neutrons get captured so that's an additional hurdle to overcome.

http://ilias.in2p3.f...7/L_Pandola.pdf
Typical flux of fast muon-induced neutrons in deep underground Labs (LNGS, Boulby) ≈ 10-9 cm-2s-1 (> 1 MeV) 1000 times smaller than neutrons from rock radioactivity.

That's .000000001 neutrons per sq centimeter per second. Remember what I showed you about needing 15 trillion years to affect .1% of atoms in a square cm with .6 muons per second. The same issue applies here except neutrons from muons are much less common than muons so the time would be even longer.


Once again you are confirming what I am saying. Deep underground rocks show old dates because the slowdown is less effected by muons which battle to penetrate to those depths. ie rocks decay close to their natural rate down there because there are fewer muons.

You also seemed to ignore the link that I posted regarding the extent of secondary neutron production from muon spallation being unknown:
https://e-reports-ex.../pdf/340911.pdf
Neutron production due to cosmic muon spallation is a constant source of background for long-dwell measurements of fissionable material. As such, it is important to understand the different underlying physical processes that contribute to neutron production via muon spallation, and their accompanying systematics. Due to the complicated interactions that lead to secondary neutrons, however, a well established theory describing this phenomena is not known.

#44 miles

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Posted 20 September 2012 - 01:26 PM

this is all very approximate. "About 300 watts" "around 880 watts". Even the 10% we are expecting is approximate, it was some scientists thumb suck that you quoted, maybe 5% is more accurate. The approximate starting energy compared to the subsequent 2 year graph just is not giving out enough information. We need second by second information during the first 3 minutes to get a good handle on this, otherwise we are wasting our time using approximate figures to try and find a small percentage difference.

Your argument is that Plutonium-238 in space will have a smaller half life (decay faster) than Pu on earth and that this decrease is large enough to challenge old earth dates. That's not a small percentage, I was using 10% as a round figure, you'd need a much bigger decrease to pose a problem which would just make things worse for your idea.

For your idea all we need to do is look at the consequences of having a different half life on earth vs. space. It doesn't matter if there's any temporary slow down on the way into space.
Half life on earth = X (plutonium-238 has a half life on earth of 87.7 years)
Half life in space = Y

Y = z * X where z is some percentage between 0 (total instant decay) and 100% (no change from earth based value)
The smaller the z value, the faster the space based substance would decay and the more power it will produce compared to the expected earth-based value.
I chose z = 90% simply because a 10% reduction is a nice round number. If you want to compress 4 billion years into a few thousand years you'd need a z of around .002% which would basically cause all RTG's in space to either melt or run out of power within a few days.

Minute by minute measurements are not needed. Even general figures are enough to show your idea doesn't work. The paper I linked showed 878W at launch day, are you willing to accept 850-900W as lower and upper bounds on the electrical power that the 3 RTG's could produce before launch? Because the power produced is proportional to the number of particle decays, if the half life becomes 10% smaller when these RTG's enter space, the power output should increase by 10%. A 10% increase using the broad range of 850-900W would mean the power would end up being between 935-990W. The power output would stay above 900W for years even at a increased decay rate. The data showed that the electrical power was never above 880W.

z=95% (this is a 5% change but remember you need more change, not less) would set that range to 892-945W. The data showed the power was never above 880W.


Once again you are confirming what I am saying. Deep underground rocks show old dates because the slowdown is less effected by muons which battle to penetrate to those depths. ie rocks decay close to their natural rate down there because there are fewer muons.

You also seemed to ignore the link that I posted regarding the extent of secondary neutron production from muon spallation being unknown:
https://e-reports-ex.../pdf/340911.pdf
Neutron production due to cosmic muon spallation is a constant source of background for long-dwell measurements of fissionable material. As such, it is important to understand the different underlying physical processes that contribute to neutron production via muon spallation, and their accompanying systematics. Due to the complicated interactions that lead to secondary neutrons, however, a well established theory describing this phenomena is not known.

That paper is trying to isolate the contribution of muons to the neutron background. It points out that the muon contribution at sea level is insignificant compared to other neutron sources.

At sea level, on the other hand, neutron production is primarily due to neutron and proton spallation.With increasing depth this source quickly loses its dominance as its yield is reduced by 3 orders of magnitude at 10 m.w.e.

If it requires a thousand-fold reduction in other sea-level neutron sources before muons begin to produce the majority of neutrons, a slight increase or decrease in muons isn't going to have much impact on overall neutron production at sea level.




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