Date: Thu, 19 May 2011 13:42:42

Author: Paul Nord

Subject: Re: Radon gas

Post:


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Tom,

Pb-214 -> 1 MeV Beta, 26 minutes
Bi-214 -> 3.2 MeV Beta, 19.9 minutes
Table of Nuclides

So, does that imply that the only decay product you're likely to see the =
3.2 MeV Beta in a Geiger counter? With the much shorter half lives of =
the other isotopes, the concentration of Pb-214 should build up to some =
saturation level after a few days of constantly collecting radon. =
Bi-214, being a shorter half-life would saturate at some much lower =
level.

I'm too lazy to figure out the saturation levels of these two isotopes. =
It not a simple exponential decay curve. It is a more complicated two =
isotope decay curve. But 45 minutes looks like a good guess.

Perhaps you're not collecting radon at all. Perhaps the Pb-214 is =
created in an ionized state.

Can you see the 1 MeV Beta if you point the end window of your geiger =
counter at the sample? (Again, I'm too lazy to search for penetrating =
power of a 1 MeV Beta. Is it Friday yet?)

Paul


On May 19, 2011, at 12:56 PM, Thomas J. Bauer wrote:

> Hi John,
>=20
> As i recall it is around 45 min half life. It comes from the daughters =
Pb -214 22min and Bi-214. 19 min. Both of these decay by beta emission. =
If you have a gamma ray spectrometer these make challenging unknowns for =
the students to find. I have attached a Uranium decay sequence that =
shows the process.
>=20
> Tom
>=20
>=20
> tap-l@lists.ncsu.edu writes:
> Tom - where does the 45 min half life come from? Radon has a 3.8 day =
half-life. Is this some effective half life from the daughters?
>=20
> -John
>=20
> Thomas J. Bauer wrote:
>=20
> =20
> tap-l@lists.ncsu.edu writes:
> I've just decided to look into whether all the radioactive sources in
> our stockroom (fiestaware, old army compasses, etc) contribute a
> significant amount of radon gas to my working environment. Has anyone
> else looked into this? I'll share what I find out, but I'll bet some =
of
> us already have some info.
> thanks
> -John
>=20
>=20
>


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Tom,Pb-214 -> 1 MeV =
Beta, 26 minutesBi-214 -> 3.2 MeV Beta, 19.9 =
minutesTable =
of NuclidesSo, does that imply that the =
only decay product you're likely to see the 3.2 MeV Beta in a Geiger =
counter? With the much shorter half lives of the other isotopes, =
the concentration of Pb-214 should build up to some saturation level =
after a few days of constantly collecting radon. Bi-214, being a =
shorter half-life would saturate at some much lower =
level.I'm too lazy to figure out the =
saturation levels of these two isotopes. It not a simple =
exponential decay curve. It is a more complicated two isotope =
decay curve. But 45 minutes looks like a good =
guess.Perhaps you're not collecting radon at =
all. Perhaps the Pb-214 is created in an ionized =
state.Can you see the 1 MeV Beta if you point =
the end window of your geiger counter at the sample? (Again, I'm =
too lazy to search for penetrating power of a 1 MeV Beta. Is it =
Friday =
yet?)PaulOn May 19, 2011, at 12:56 PM, Thomas J. Bauer wrote:Hi =
John,As i recall it is around =
45 min half life. It comes from the daughters Pb -214 22min and Bi-214. =
19 min. Both of these decay by beta emission. If you have a gamma ray =
spectrometer these make challenging unknowns for the students to find. I =
have attached a Uranium decay sequence that shows the =
process.tap-l@lists.ncsu.edu writes:Tom - where does the 45 =
min half life come from? Radon has a 3.8 day half-life. Is this some =
effective half life from the daughters?Thomas J. Bauer wrote:I've just decided to look into whether all =
the radioactive sources inour stockroom (fiestaware, old army =
compasses, etc) contribute asignificant amount of radon gas to my =
working environment. Has anyoneelse looked into this? I'll share what I =
find out, but I'll bet some ofus already have some =
info.

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