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RE: Color TV screens as radon daughter collectors
David:
I did an informal study using dust from TV's to find radon daughter products. My recollection of some facets is a little fuzzy, but here are some tips:
1) There must be radon/thoron present. A TV in a basement is more likely to pickup the "contaminated" dust than upper level locations. It also helps to have a dusty environment (Nebraska where I did this was no problem). You will rarely find detectable levels of radon in a positive pressure building, as seen in most office buildings and many schools, so don't bother to look for it in those locations. I suggest home TV's would be best. Despite what the EPA says publicly, the EPA studies show that it makes no difference if the home is "tight" or "loose". The key is how much Radon is in the soil, and how much negative pressure is on the floor/walls associated with the soil (gaseous diffusion due to pressure differential). For example, Winter heating of a home causes a negative pressure on the basement floor as the hot air rises.
2) Static buildup on a TV screen is highly dependent on the manufacturer. It always bleeds off. Some TV's build up static upon initially being energized, others upon being de-energized. If I remember correctly, rarely does the static level remain high during operation. We found that on some TV's, as the static dissipated, so did the dust. You will have to play with this to find the best collectors, but is easy to determine when the static is building up, put your arm hairs close to the screen.
3) I only found a few wipe samples that I could count with a pancake G-M meter. I did not use a NaI or uR survey detector, so you might try and see if one of these would work. Most ion chambers are way too insensitive to measure the levels on the wipes. I also used both a liquid scintillation counter and a NaI-MCA. with these detectors, I found some spectacular activities and a lot of no activity samples. Having access to a MCA is nice as it allows you to determine if you are collecting radon daughter products or thoron products. Of course, if you wait a couple of days before counting, the thoron products decay away.
4)I used standard Whatman filter paper to take the wipes, but most any semi-absorbent paper will work. If you use highly absorbent paper (paper towel, toilet paper, or tissues) you will lose a lot of the beta's by absorption in the paper.
Hope this helps
Larry Grimm, Senior HP
UCLA EH&S/ Radiation Safety Division
* lgrimm@admin.ucla.edu Phone:310/206-0712 Fax: 310/206-9051
Cell: 310/863-5556 Pager:1-800-233-7231ext93569
* On Campus: 501 Westwood Plaza, 4th Floor, MS 951605
* Off Campus: UCLA Radiation Safety Div, 501 Westwood Plaza 4th
Fl, Box 951605, Los Angeles, CA 90095-1605
* If this email is not RSD business, the opinions are mine, not
UCLA's.
-----Original Message-----
From: North, David [mailto:DNorth@LIFESPAN.ORG]
Sent: Friday, November 15, 2002 8:10 AM
To: 'RADSAFE'
Subject: Color TV screens as radon daughter collectors
Dear Radsafers,
I know this subject has come up on the List before, but I wasn't paying
really close attention. Now my daughter needs some sort of science project,
and I thought it might be possible for her to assay some airborne dust
(hopefully laden with radon daughters) that collects on TV and PC monitor
screens. Are there any tips out there for doing this? What's good for
cleaning the screens? What's good for counting, a thin-window GM? How long
does the TV have to be powered on to collect enough?
Any help will be much appreciated. If my daughter is happy, the whole family
will be happy!
David L. North, Sc.M. DABR
Associate Physicist
Department of Medical Physics
Main Bldg Rm 317
Rhode Island Hospital
593 Eddy St.
Providence, RI 02903
ph: (401)444-5961
fax: (401)444-4446
dnorth@lifespan.org
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