RE: Color TV screens as radon daughter collectors

[alstonchris@netscape.net]

Larry



This is your usual interesting and helpful comment.  I'm compelled to make one small clarificaton.  If she counts her wipe (or the screen itself, for that matter) immediately, she'll see a mix of radon and thoron "daughters".    Then, if she waits about four (4) hours, the radon daughters will have decayed away, and she'll be left with thoron daughters, which will fade over the next four (4) days.



There's actually some ingrowth of thoron daughters, initially.  And, what's more there's a whole little protocol for the gross alpha counting of radon/thoron daughters, the Kusnetz method, which enables one to make semi-quantitative determinations of what's there, based on counts obtained at specified intervals post-sampling.  Perhaps one of the DOE remedial action folks has a copy around.



Cheers

cja







"Grimm, Lawrence" <LGrimm@FACNET.UCLA.EDU> wrote:

>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.





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