Date: Thu, 19 May 2011 15:50:01

Author: Thomas J. Bauer

Subject: Re: Radon gas

Post:

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tap-l@lists.ncsu.edu writes:
>Tom,
>
>
>Pb-214 -> 1 MeV Beta, 26 minutes
>Bi-214 -> 3.2 MeV Beta, ¬ 19.9 minutes
>[ http://atom.kaeri.re.kr/ton/nuc8.html ]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,
>
>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.
>
>Tom
>
>
>[ mailto:tap-l@lists.ncsu.edu ]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?
>
>-John
>
>Thomas J. Bauer wrote:
>
>¬ ¬ ¬
>[ mailto:tap-l@lists.ncsu.edu ]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
>
>
>
>



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tap-l=40lists.ncsu.edu writes:
Tom,


Pb-214 -> 1 MeV Beta, 26 minutes
Bi-214 -> 3.2 MeV Beta, =C2=A019.9 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? =C2=A0With the m=
uch shorter half lives of the other isotopes, the concentration of Pb-214 s=
hould build up to some saturation level after a few days of constantly coll=
ecting radon. =C2=A0Bi-214, being a shorter half-life would saturate at som=
e much lower level.


I'm too lazy to figure out the saturation levels=
of these two isotopes. =C2=A0It not a simple exponential decay curve. =C2=
=A0It is a more complicated two isotope decay curve. =C2=A0But 45 minutes l=
ooks like a good guess.


Perhaps you're not collecting radon at all. =C2=
=A0Perhaps 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? =C2=A0(Again, I'm too lazy to =
search for penetrating power of a 1 MeV Beta. =C2=A0Is it Friday yet?)


Paul



On May 19, 2011, at 12:56 PM, Thomas J. Bauer wr=
ote:



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. B=
oth of these decay by beta emission. If you have a gamma ray spectrometer t=
hese make challenging unknowns for the students to find. I have attached a =
Uranium decay sequence that shows the process.

Tom


tap-l=40lists.ncsu.edu=C2=A0writes:<=
/span>
Tom - whe=
re does the 45 min half life come from? Radon has a 3.8 day half-life. Is t=
his some effective half life from the daughters?

-John

Thomas J.=
Bauer wrote:

=C2=A0=
=C2=A0=C2=A0
tap-l=40lists.ncsu.edu=C2=A0writes:<=
/span>
I've just decided to look int=
o whether all the radioactive sources in
our stockroom (fiestaware, ol=
d army compasses, etc) contribute a
significant amount of radon g=
as to my working environment. Has anyone
else looked into this? I'll s=
hare what I find out, but I'll bet some of
us already have some info.
thanks
-John


um Decay sequence.doc>






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