
Analysis of Soviet smoke detector plutonium - cc_
https://carlwillis.wordpress.com/2017/02/07/analysis-of-soviet-smoke-detector-plutonium/
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exabrial
"... the guest bedroom of the home (the least radioactive room, as it should
be)..."

I think that's my new favorite quote from a scientist.

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ChristianGeek
What was your previous one?

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exabrial
42

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gumby
Hey kids, if you plan to play with Pu, what the author fails to mention is
that it is not only radioactive but actually poisonous (chemically) as well.

On the other hand, another little known fact is that you can weld it, which
isn't true of all metals.

~~~
anfractuosity
That's interesting with respect to welding. I just assumed all metals could be
welded, do you know the reason why some can't out of interest.

Also is plutonium welded for any application, out of curiosity?

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petee
One reason certain metals can't be welded is how their crystalline structure
is altered by the process, creating a weak or brittle weld/HAZ (heat affected
zone: weaker metal surrounding the weld/filler metal altered by heat)

Some metals also have difficult or impossible cooling rates - welding
stainless to carbon steel will make a weak weld that is almost guaranteed to
crack while cooling because one metal cools and contracts much faster than the
other.

The topic is fairly complex, but there is a good textbook/reference for
welders put out by the Lincoln Arc Welding Foundation called "Metals and How
To Weld Them" that goes deep on structure and metallurgy, in a readable way.

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gene-h
Doc Brown was probably right: "that in 1985, plutonium is available in every
corner drugstore," in the Soviet Union at least.

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mmmBacon
Reminds me of David Hahn, a kid who tried to make a breeder reactor in a
garden shed. He massed Americium from smoke detectors in an attempt to make
Plutonium.

[https://en.m.wikipedia.org/wiki/David_Hahn](https://en.m.wikipedia.org/wiki/David_Hahn)

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seesomesense
[https://en.wikipedia.org/wiki/David_Hahn#Death](https://en.wikipedia.org/wiki/David_Hahn#Death)

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petee
Probably important to highlight that he was 39 when he died...

I always admired his passion, but puzzled at his stubborn lack of safety
precautions.

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frozenport
If I recall, the cause of death was "unatural" and years of mental health
problems hint that he didn't die of radiation related diseases.

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petee
Thats what I had recalled, until I found his mugshot when he was arrested
stealing smoke detectors - his face was covered in lesions attributed to
radiation. Pretty sad. If it wasn't the immediate cause, it likely wasn't
unrelated either.

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noir-york
Great science writeup!

The Tsar Bomba described as a "the noble purpose of containing capitalist
imperialism" \- great quote :)

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URSpider94
This has to be the best amateur science write-up I have seen in years, maybe
ever.

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lokedhs
Although the author is a professional nuclear engineer, I do agree with you on
the quality of the writing.

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URSpider94
I didn't look at his bio, but I assumed that he must do something in the field
in his day job -- it would be really hard to stockpile this much knowledge
from scratch, even with the help of the Internet ...

Nonetheless, he did this with the gamma spectrometer in his spare room ...

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wycx
Note that a high purity Germanium detector requires LN cooling to operate, and
judging by the size of the dewar on his detector, would need filling maybe
once a week to keep it cool all the time.

That is a bit onerous if you only play with it every now and then and don't
have a 20000 L LN tank in your backyard.

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Reason077
Modern smoke detectors seem to have done away with ionization in favour of
optical technology, and so no longer contain radioactive materials.

Bad news for mad scientists!

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anfractuosity
Are you sure about that, I thought ones with Americium were more sensitive?
I'm pretty sure you can still get both.

Edit: Seems I'm not right regarding sensitivity, wiki says:

"Ionization detectors are more sensitive to the flaming stage of fires than
optical detectors, while optical detectors are more sensitive to fires in the
early smouldering stage"

Wow it also says:

"Where an ionizing smoke detector has been the only detector, fires in the
early stages have not always been effectively detected."

That's worrying.

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Reason077
Less sensitivity (or rather, being able to have a higher threshold for
sounding the alarm) is actually a good feature for general domestic
applications.

You don't really want the thing going off every time someone burns a bit of
toast or it just becomes an annoyance, and therefore at risk or being removed
or disabled.

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anfractuosity
Yeah that's true, I guess personally though I'd rather put up with some false
positive alarms from toast etc.

