Irradiated Dimes (2010)(orau.org)
orau.org
Irradiated Dimes (2010)
https://www.orau.org/ptp/collection/medalsmementoes/dimes.htm
38 comments
But WHY do this at all? Is it because of public fascination with anything "atomic"? Good public relations? I don't get it. Because of little or no residual effects, why not just press the times into a souvenir holder and skip the irradiation altogether? It all just seems odd to me.
It's a demonstration of neutron irradiation. The lack of residual effects does not negate the coin becoming directly associated with that demonstration in memory.
If it helps making people aware of the process that's a good thing. Think about radioactive waste.
If it helps making people aware of the process that's a good thing. Think about radioactive waste.
This is the cheap go-to method for fusor enthusiasts to check for fast neutron production.
Scarcity, and being able to prove that you went there and got your dime irradiated.
Anyone could press a dime into a fancy container, but a fake could be easily detected with a geiger counter. There was no other way to irradiate dimes at the time.
Anyone could press a dime into a fancy container, but a fake could be easily detected with a geiger counter. There was no other way to irradiate dimes at the time.
>The only activity that might be detected today would be due to trace quantities of Ag-108m, but it would require long counts and relatively sophisticated equipment. I could not detect any in the three coins in the collection.
I can see the fascination. In a way it's a philosopher's stone turning one element(silver) into another(cadmium). Of course the reaction is in the opposite way you'd want it to go but still.
> But WHY do this at all?
"I have seen the future, and it works", an infamous phrase if there ever was one, did not come out of the blue.
For three centuries now, we've been groomed to expect bountiful marvels out the "unstoppable progress" of history. Which, incidentally, is a novel concept, not present in human discourse before the XVIII century.
"I have seen the future, and it works", an infamous phrase if there ever was one, did not come out of the blue.
For three centuries now, we've been groomed to expect bountiful marvels out the "unstoppable progress" of history. Which, incidentally, is a novel concept, not present in human discourse before the XVIII century.
I wonder whether the dimes remained legal tender in this process. You could have paid a parking fine with a stack of them...
The great answer to "Why" is "because you can".
Yes, both of those things. You have to keep in mind this is the era immediately following WW2, so there was both a fascination with and fear of things "atomic."
Reading this introduced me to the phenomenon of meta-stable nuclear isomers: states of atomic nuclei of an isotope which are more stable than the ground state of that isotope. (including the metastable isomer of 180m
73Ta, which is present in all tantalum samples at about 1 part in 8,300. Its half-life is at least 1015 years, markedly longer than the age of the universe.)
> Gamma neutron sources inevitably have two problems. First, the gamma emitter is short-lived. Sb-124 has a 60 day half-life which meant that it had to be periodically reactivated in a reactor. Second, the gamma source presents an exposure hazard that requires lead shielding.
A family member was working in a facility selling Californium-252, a strong neutron emitter. So gamma sources might be awkward to work with but these things are not exactly fun to work with either.
It's probably the most expensive commercially sold substance on earth ($20M+ / gram). The half life is only 2 years. Now that's a nice revenue stream, well as long as Oak Ridge keeps its reactor going and there are enough customers out there.
Also due to being a strong neutron emitter, it has a ridiculous amount of shielding. Lead won't work for it like it does for gamma rays, but things like polyethylene work well. So there would be lots of it, even for a tiny amount like a tiny fraction of a gram.
A family member was working in a facility selling Californium-252, a strong neutron emitter. So gamma sources might be awkward to work with but these things are not exactly fun to work with either.
It's probably the most expensive commercially sold substance on earth ($20M+ / gram). The half life is only 2 years. Now that's a nice revenue stream, well as long as Oak Ridge keeps its reactor going and there are enough customers out there.
Also due to being a strong neutron emitter, it has a ridiculous amount of shielding. Lead won't work for it like it does for gamma rays, but things like polyethylene work well. So there would be lots of it, even for a tiny amount like a tiny fraction of a gram.
> A family member was working in a facility selling Californium-252
Did he sell to government, or basically anybody could buy isotopes just like that?
Did he sell to government, or basically anybody could buy isotopes just like that?
Bought from government (Oak Ridge) and sold to customers. Some are governments some are companies which use it for diagnostics like say detect structural issues in concrete. I think there are medical uses as well.
As far as who can buy it and what the approval process is? I imagine there are controls in place. I never inquired about that.
As far as who can buy it and what the approval process is? I imagine there are controls in place. I never inquired about that.
Depending on the amount, a license would be required.
Here's a link to current limitations: https://www.nrc.gov/reading-rm/doc-collections/cfr/part030/p...
Link regarding exempt amounts:https://www.nrc.gov/reading-rm/doc-collections/cfr/part030/p...
Here's a link to current limitations: https://www.nrc.gov/reading-rm/doc-collections/cfr/part030/p...
Link regarding exempt amounts:https://www.nrc.gov/reading-rm/doc-collections/cfr/part030/p...
Ah interesting. Apparently there is no exempt quantity of Cf-252.
Well I just found out that I was grossly underestimating the danger of handling Cf-252, given its half-life.
Look what ORNL used to transport 1g: https://en.m.wikipedia.org/wiki/Californium#/media/File%3ACf...
Look what ORNL used to transport 1g: https://en.m.wikipedia.org/wiki/Californium#/media/File%3ACf...
Yeah. A single fission event can generate 2-4 neutrons, so even a tiny spec can be pretty dangerous.
Here are the drums used for shipping much smaller amounts:
http://www.frontier-cf252.com/custom-type-a-packaging-radioa...
Here are the drums used for shipping much smaller amounts:
http://www.frontier-cf252.com/custom-type-a-packaging-radioa...
What makes polyethylene a good neutron shielding and lead not?
Not a physicist but I was explained it was like this:
Anything that has a mass close to the mass of the neutron would work better because we'd want to have a lot of elastic collisions to slow neutrons down. So something with lots of hydrogen would work, since the nucleus of hydrogen is a single proton so about the same mass as a neutron. It would mean water works. But so does polyethylene and it can be molded into various shapes and doesn't leak like water.
Another way to think about it is lead is heavy nucleus, imagine it like a bowling ball. A neutron on other hand are more like tennis balls. A fast flying tennis ball hitting a bunch of bowling balls will not slow down too much and will keep bouncing around at at high speed.
Now imagine this fast tennis ball hitting lots other tennis balls. Then the collisions are more elastic and it will slow down the neutron quicker.
Anything that has a mass close to the mass of the neutron would work better because we'd want to have a lot of elastic collisions to slow neutrons down. So something with lots of hydrogen would work, since the nucleus of hydrogen is a single proton so about the same mass as a neutron. It would mean water works. But so does polyethylene and it can be molded into various shapes and doesn't leak like water.
Another way to think about it is lead is heavy nucleus, imagine it like a bowling ball. A neutron on other hand are more like tennis balls. A fast flying tennis ball hitting a bunch of bowling balls will not slow down too much and will keep bouncing around at at high speed.
Now imagine this fast tennis ball hitting lots other tennis balls. Then the collisions are more elastic and it will slow down the neutron quicker.
And this is exactly the sort of principle that helps to distinguish between the mechanical aspects of quantum physics, and the much-hyped angular momentum spin uncertainty aspects.
People make so much hay about the curious non-locality and uncertainty of spin, and tend to get tunnel vision about how nothing makes sense anymore, leaving out the broader strokes which have pretty reasonable underlying principles.
People make so much hay about the curious non-locality and uncertainty of spin, and tend to get tunnel vision about how nothing makes sense anymore, leaving out the broader strokes which have pretty reasonable underlying principles.
A lead nucleus is much heavier than a neutron. Think of a billiard-ball colliding with a bowling ball -- the bowling ball is hardly affected and the billiard-ball keeps most of its energy even if it changes direction.
But a hydrogen nucleus is just a proton, and thus about the same mass as a neutron. So this results in lots of energy transfer, just as with billiard-balls hitting one another.
Like many plastics, polyethylene has lots of hydrogen atoms. Sticking them onto a carbon spine is a very efficient way to pack lots of hydrogen nuclei into a given volume of space.
But a hydrogen nucleus is just a proton, and thus about the same mass as a neutron. So this results in lots of energy transfer, just as with billiard-balls hitting one another.
Like many plastics, polyethylene has lots of hydrogen atoms. Sticking them onto a carbon spine is a very efficient way to pack lots of hydrogen nuclei into a given volume of space.
Let's say you have a neutron shooting through some solid matter, you have a couple things that can happen. One is that the neutron can just not get close to any nuclei. This depends on the density and thickness of the matter the neutrons pass through. Another is that the neutron can come close to a nucleus and scatter off of it. Or, a neutron can come close to a nucleus and either be absorbed by it or cause some neutronic nuclear reaction (such as neutron induced fission).
There are two super interesting things that are relevant to neutron scattering off of Hydrogen nuclei (protons). One is that due to quantum effects the de Broglie wavelength of the proton is larger than for other nuclei (partly due to the standard inverse relationship between energy and wavelength). This means that protons are a much larger "target" than more massive nuclei in terms of neutron scattering, which is a bit opposite of what you might imagine from a non-quantum perspective. Additionally, protons and neutrons are nearly the same exact mass, within single digit percentage points. Now, let's say you take a tennis ball and you throw it at a wall, it'll bounce off the wall at nearly the same speed, right? And almost exactly the same thing will happen if you throw it at a bowling ball. This is just the way momentum and kinetic energy works. But if you throw a tennis ball at another tennis ball and you hit it dead on then you'll transfer all of the momentum from the first ball to the second, just as in a Newton's Cradle or in a game of billiards.
Those two facts together mean that Hydrogen nuclei are super good at slowing down neutrons. They are much larger targets to the neutrons and when neutrons scatter off of them the neutrons tend to lose a lot of their momentum. So it doesn't take many scatterings before the neutrons are no longer at ionizing energy levels and aren't dangerous to humans (they will decay with a half-life of several minutes into protons and electrons (and neutrinos)). Meanwhile, those protons will get a ton of momentum foisted onto them, but they are charged particles moving through atomic matter chock-a-block with other charged particles so they don't get far. The net result is that neutron radiation is blocked.
Polyethylene is basically (CH2)n so it contains lots of Hydrogen atoms (water is also a good neutron moderator/blocker). Additionally, Carbon is also one of the better neutron moderators, so the combination is pretty effective.
On the other hand, lead is just a bunch of heavy nuclei. Which aren't actually that "big" from a neutron's perspective due to quantum effects, and most of the time when a neutron hits a lead nucleus it's just going to ricochet and maintain almost 100% of its original speed/energy, so you need a lot of lead to make a difference.
There are two super interesting things that are relevant to neutron scattering off of Hydrogen nuclei (protons). One is that due to quantum effects the de Broglie wavelength of the proton is larger than for other nuclei (partly due to the standard inverse relationship between energy and wavelength). This means that protons are a much larger "target" than more massive nuclei in terms of neutron scattering, which is a bit opposite of what you might imagine from a non-quantum perspective. Additionally, protons and neutrons are nearly the same exact mass, within single digit percentage points. Now, let's say you take a tennis ball and you throw it at a wall, it'll bounce off the wall at nearly the same speed, right? And almost exactly the same thing will happen if you throw it at a bowling ball. This is just the way momentum and kinetic energy works. But if you throw a tennis ball at another tennis ball and you hit it dead on then you'll transfer all of the momentum from the first ball to the second, just as in a Newton's Cradle or in a game of billiards.
Those two facts together mean that Hydrogen nuclei are super good at slowing down neutrons. They are much larger targets to the neutrons and when neutrons scatter off of them the neutrons tend to lose a lot of their momentum. So it doesn't take many scatterings before the neutrons are no longer at ionizing energy levels and aren't dangerous to humans (they will decay with a half-life of several minutes into protons and electrons (and neutrinos)). Meanwhile, those protons will get a ton of momentum foisted onto them, but they are charged particles moving through atomic matter chock-a-block with other charged particles so they don't get far. The net result is that neutron radiation is blocked.
Polyethylene is basically (CH2)n so it contains lots of Hydrogen atoms (water is also a good neutron moderator/blocker). Additionally, Carbon is also one of the better neutron moderators, so the combination is pretty effective.
On the other hand, lead is just a bunch of heavy nuclei. Which aren't actually that "big" from a neutron's perspective due to quantum effects, and most of the time when a neutron hits a lead nucleus it's just going to ricochet and maintain almost 100% of its original speed/energy, so you need a lot of lead to make a difference.
"Since the carriers were not sealed, there is no certainty that a dime they hold today had ever been irradiated."
Unless one owned a Geiger counter, I would argue that it is entirely possible that the dime held when it was "irradiated" had not ever been irradiated. When I was reading the article, my thinking was that if no one had actually confirmed that this took place I'd be reading an article about scam artists in the 50s and 60s selling "irradiated" dimes.
Unless one owned a Geiger counter, I would argue that it is entirely possible that the dime held when it was "irradiated" had not ever been irradiated. When I was reading the article, my thinking was that if no one had actually confirmed that this took place I'd be reading an article about scam artists in the 50s and 60s selling "irradiated" dimes.
Even with a geiger counter, you wouldn't be able to tell, as the longest half life of any of the isotopes created was ~12 hours, and the most common one was 22 seconds. There's basically no radioactivity left in these dimes after a few hours, let alone 50 years.
The article says that the apparatus included a Geiger counter, so that the dime was visibly shown to be radioactive before being encased.
The article says that the apparatus included a Geiger counter
A Geiger counter, or a device that makes clicky noises? I'm not disputing the article, I'm willing to believe that the device contained an actual Geiger counter. But in isolation, my point is that this could just as easily be some scam similar to the chess-playing machine that really had a human inside of it. "These dimes have been irradiated with invisible particles! But look, I have a device that clicks in the presence of those magic, invisible particles!" Clicks, huh? Oh, realllly.
And, based on another sibling comment, it was almost a scam in that the radioactive decay was so fast that the dimes might not even make it home before all of the radioactivity went away. In the end, all we have left is a dime that might, or might not, have at one time been irradiated. But even if we could prove it then, we have no way of proving it now.
A Geiger counter, or a device that makes clicky noises? I'm not disputing the article, I'm willing to believe that the device contained an actual Geiger counter. But in isolation, my point is that this could just as easily be some scam similar to the chess-playing machine that really had a human inside of it. "These dimes have been irradiated with invisible particles! But look, I have a device that clicks in the presence of those magic, invisible particles!" Clicks, huh? Oh, realllly.
And, based on another sibling comment, it was almost a scam in that the radioactive decay was so fast that the dimes might not even make it home before all of the radioactivity went away. In the end, all we have left is a dime that might, or might not, have at one time been irradiated. But even if we could prove it then, we have no way of proving it now.
The presence of Cadmium-110 could serve as a good indicator, assuming that the process added enough and there wasn't too much Cadmium-110 in the original coins.
Cools, thanks. I figured there was some atomic particle marker thingy that would hang on to be detected later. But I'm pretty ignorant when it comes to stuff that rots by flinging dangerous particles at other stuff.
I still have one of these from the 1964 World's Fair. I figure it's worth at least - oh - ten cents.
At least ten cents. Sure, but I'll buy as many 1964 dimes as you have got for a dollar each.
njarboe is trying to get the silver, don't let him!
https://www.ngccoin.com/price-guide/coin-melt-values.aspx
https://www.ngccoin.com/price-guide/coin-melt-values.aspx
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I was 7 or 8. The future seemed closer then, like we were almost just right there. “Atomic energy,” the space program, television: I remember when WAND in Decatur started broadcasting in color. Everything was getting better right in front of our eyes. Cool Whip! One day it was THERE.
And so on a visit to Oak Ridge, TN, you felt as a kid that it was all happening, that you could learn about it, and when you grew up you could join the team and make it happen, too. The dime was proof.