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RE: TV radiation
If the location of the TV is in a relatively high radon/thoron area, the dust which collects on the screen will likely have daughter products attached. The polonium ion, after decay, is usually positively charged and grabs the first thing it can find, i.e. dust in the air. I did an informal study on it and found that it's an interesting way to measure Radon/Thoron, but it is highly dependent on how static builds up on the TV. This seemed to be manufacturer and model dependent.
The experiment was cut short when my wife did not buy my contention that our house should remain dusty until I finished the experiment. Albeit the daughter product radiation dose from a dusty TV would be very small, I used it as an excuse to discourage my children's' TV watching. It didn't work very well - but then they were always smarter than me.
I concur with Ted DeCastro regarding the definitive article in the HPS Journal. TV screen radiation is not a problem. The question of TV screen radiation comes up periodically in the public. I recommend that you keep copies of this article in your file. At least once a year I hand out a copy to a "concerned" citizen. Regarding the radon/thoron daughter buildup, use Windex regularly or turn off your TV indefinitely.
Larry Grimm, Senior HP
UCLA EH&S/ Radiation Safety Division
-----Original Message-----
From: Ted de Castro [mailto:tdc@XRAYTED.COM]
Sent: Monday, November 04, 2002 11:44 AM
To: Stephen Mecca
Cc: Bjorn Cedervall; radsafe@list.vanderbilt.edu
Subject: Re: another reaction to the Pittsburg TMI "study"
Yes - that is what I was commenting on as well. While a x-ray tube is
glass and has a vacuum as well - it usually has a small thinner section
as a window or even other material like Be for these lower energies.
Beyond that x-ray tubes tend to be an inherently stronger cylindrical
design. CRT's on the other hand have a very large flat face which
requires considerable thickness to support the vacuum and even more so
to hold the face flat and to do so against a disadvantageous geometry.
I would invite you to check the most definitive article I have seen on
the subject:
"Low-background Radiation Measurements on Video Display Terminals"
Health Physics VOl 46 no 2 pp 413 - 417, 1984.
There is really nothing in that article that does not apply to today's
CRT's.
Stephen Mecca wrote:
>
> Thanks for this information, Ted and Bjorn:
> I was not thinking of the power supplies as the source but rather the
> Bremsstrahlung produced as the electrons are decelerated by the screen
> materials. The glass is strong enough to hold a vacuum, but so is an
> x-ray tube's glass strong enough to support a vacuum. I know that the
> manufacturers are not using the high lead glass. While I'm quite sure
> you are right about the fact that the dose is low, I'm curious as to
> what the level might be. I'm wondering if it has been measured.
> Thanks for your help on this.
> ..Steve Mecca
> Ted de Castro wrote:
>
> > You can't get that much from a TV or CRT - except a projection CRT.
> > These devices haven't put out significant x-rays since they went to
> > solid state high voltage power supplies many many years ago.
> > As for x-rays from the face ... the materials the beam can strike
> > does
> > not have a high cross section for x-ray production and the thickness
> > of
> > the glass required to stand the forces of the vacuum is more than
> > enough
> > shielding.
> > It just doesn't happen!
> > This was one of those bad cases to use a film badge - in this energy
> > region it over responds.
> > Bjorn Cedervall wrote:
> >
> >> My friend "Steve" (professor and physicist - not on Radsafers) -
> >> sent me the
> >> question below. Please help Steve with relevant information:
> >> smecca@providence.edu
> >> Thanks in advance,
> >> Bjorn Cedervall bcradsafers@hotmail.com
> >> -----------------------------------------
> >> I have a question you might be able to help me with. Do you have
> >> any
> >> information as to risks of somatic or genetic effects of X-Rays
> >> from TV or
> >> Computer monitors. The breaking radiation from the face of a
> >> monitor will
> >> have maximum energy X-Rays in the 20-25 KeV region. An old friend
> >> of mine,
> >> with whom I've lost contact, some years ago put an X-Ray film on a
> >> monitor
> >> screen and determined that in order to get 100 mR per week (the
> >> allowable
> >> limit) one would have to wrap oneself around the monitor and be in
> >> co
> >> ntact
> >> with it. Nevertheless, I have this sense that, with the low prices
> >> of LCD
> >> screens, it might be worthwhile for schools such as ours to
> >> consider orderly
> >> replacements of the older tube monitors. Any thoughts, references
> >> or wisdom
> >> on this?
> >> _________________________________________________________________
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