
Irradiated Dimes (2010) - chaosmachine
https://www.orau.org/ptp/collection/medalsmementoes/dimes.htm
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keenrodent
I’ve still got one of these (a dime from my Dad’s pocket, irradiated, then
into the box with the rest of my kid treasures) from when my family and I
visited Oak Ridge in the 60’s. I can’t speak to why they had the machine to do
it there, but I still remember why I put the dime in.

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.

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codewritinfool
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.

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the8472
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.

~~~
badmin_
This is the cheap go-to method for fusor enthusiasts to check for fast neutron
production.

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MaysonL
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.)

~~~
nielsbot
10^15?

~~~
klodolph
Yes, although Wikipedia says that the estimated lower bound is 45x10^15 years.

~~~
terminado
I was about to say, maybe it was supposed to be 1,015 of some other kind of
unit of time.

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rdtsc
> 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.

~~~
pmiller2
What makes polyethylene a good neutron shielding and lead not?

~~~
rdtsc
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.

~~~
terminado
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.

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mikestew
_" 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.

~~~
moioci
The article says that the apparatus included a Geiger counter, so that the
dime was visibly shown to be radioactive before being encased.

~~~
mikestew
_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.

~~~
tgsovlerkhgsel
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.

~~~
mikestew
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.

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tallpapab
I still have one of these from the 1964 World's Fair. I figure it's worth at
least - oh - ten cents.

~~~
njarboe
At least ten cents. Sure, but I'll buy as many 1964 dimes as you have got for
a dollar each.

