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Re: external alpha exposure limits (was: taking apart smoke detec tors)



John,
My message should be interpreted as saying that yes it is safe
and we know it. But do Mr. and Mrs. Smith?? The general public lives
in fear of the word radiation. Any mention of doing a lab on radiation
will probably cause a scare in those that aren't as educated as most of
us on this matter. All you need is the wrong people with the right
friends in the system cause serious hell for you. For me, it doesn't
seem worth the trouble to have this hanging over my head.
As for pregnant women, it is federal law that once they decide
to disclose the pregnancy they must be monitored to ensure they don't
recieve more than 50 mrem over the gestation period. That is even if it
is alphas that won't reach the fetus, because the higher ups want their
ass covered just in case there is a birth defect. That way the mother
can't say it was caused by exposure than you have to spend all the time
going to court to prove it.
Again, I am not saying that it is not safe and appears to be
legal. My problem is that I don't want to have to deal with the people.


Sam Held



-----Original Message-----
From: John Denker [mailto:jsd@MONMOUTH.COM]
Sent: Wednesday, April 21, 1999 12:47 PM
To: PHYS-L@LISTS.NAU.EDU
Subject: Re: external alpha exposure limits (was: taking apart smoke
detectors)


Hi Folks --

I don't get it. Here's what has been said so far:
1) The emitter is typically Americium.
2) It can be diffused into a metal carrier, from which it cannot
easily
be removed.
3) There are strict exposure limits for this sort of radiation, and
the
limits are stricter for pregnant persons.

To this I add a couple of physical facts:
4) Americium puts out alphas at 5.4 MeV.
5) The stopping range for alphas in this energy range is something
like
0.04 mm of water (i.e. very small compared to the thickness of your
skin).

So just what is the threat model here? Just how are these alphas going
to
get to the fetus? Is there an exposure limit for ingested alpha
emitters,
distinct from non-ingestible alpha emitters? Do the regulations spell
out
to what lengths one must go to make something non-ingestible? Or am I
asking for rationality in a field where rationality is largely absent?

Thanks --- jsd