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Re: Detectors and humidity
Air density decreases with increased relative humidity. It's because you
are displacing heavier molecules (O2, N2) with lighter ones (H2O). Ask any
pilot.
Vincent King
Grand Junction, CO
----- Original Message -----
From: <John_Sukosky@DOM.COM>
To: <jjshonka@Shonka.Com>
Cc: <radsafe@list.vanderbilt.edu>
Sent: Tuesday, June 01, 2004 4:47 AM
Subject: RE: Detectors and humidity
Joe,
I'll take you up on your offer of the equation that shows the density of
air is reduced with humidity. I've had much interest in this, both on and
off the Radsafe list. It's not intuitively obvious (one would expect air
density to increase with an increase in humidity and therefore less alpha
efficiency at higher humidity).
Thanks,
John M. Sukosky, CHP
Dominion
Surry Power Station
(757)-365-2594 (Tieline: 8-798-2594)
----- Forwarded by John Sukosky/NUC/VANCPOWER on 06/01/04 06:39 AM -----
"Riely, Brian P."
<brian.riely@ngc. To:
John_Sukosky@DOM.COM
com> cc:
Subject: RE: Detectors and
humidity
05/28/04 03:00 PM
Hi John
Joe said
"As for correlated causes, for example, the density of air is reduced with
humidity (I can get you an equation if you like)..."
When Joe gets time, I would like the equation.
Brian
-----Original Message-----
From: John_Sukosky@DOM.COM [mailto:John_Sukosky@DOM.COM]
Sent: Friday, May 28, 2004 1:06 PM
To: radsafe@list.vanderbilt.edu
Subject: Detectors and humidity
----- Forwarded by John Sukosky/NUC/VANCPOWER on 05/28/04 01:05 PM -----
"Joseph J.
Shonka" To:
<John_Sukosky@DOM.COM>
<jjshonka@shonka. cc: <JPreisig@AOL.COM>
com> Subject: Detectors and
humidity
05/28/04 10:39 AM
Dear John (and Joe):
I am not allowed to look at RADSAFE, since I would waste a good fraction of
the day, but someone forwarded your exchange to me. First things first,
Joe I hope you were talking about someone else J.
John
I don’t think the supply voltage is the issue. Although 3 systems are
correlated with humidity, I think that you could be dealing with more than
one cause with the causes correlated seasonally not the supply voltage.
However, if you are talking about outages with offsite power I may
reconsider voltage.
As for correlated causes, for example, the density of air is reduced with
humidity (I can get you an equation if you like), and that may explain the
increased alpha background as a function of humidity, especially for low
energy alpha. As for the gamma sensitive detectors, Joe Preisig is
correct. If you “in situ gamma spec” one point on earth every day, you
find the equivalent uranium (from Bi-214) is higher in the wet season
because the small fraction of total radon in soil that emanates to air
increases in wet soil. Have you looked at any beta CAMs (that do not have
radon subtraction)? You would need to look at the same time of day (avoid
mid morning, perhaps midafternoon) and look at a few months of winter
versus summer. The radon you measure comes from a location a day or two
“upwind” of you, which may have greater seasonal variation than your
location.
I am not a member of RADSAFE, but you are free to post my hypothesis if you
like.
Regards and good luck,
Joe Shonka
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