🚀 go-pugleaf

On 6-MAY-1995  Mark Sylvester <msylvester@GN.APC.ORG>, referring to my problem,

    "  ... as far as I know, the Rn-222 chain does not contain any isotope
           whose half-life is close to 70 mininute."  ...

wrote:

>       But according to Jim Riley, we are getting the 70 minute result
>       becase of the combined effect of the Pb214 ->> Bi214 ->> Po214 chain.

At the end of his interesting message he adds:

>       .... you have lots of radon round your TV!
>                                                         Mark.

Yes, most of the radioactivity from my Toshiba at home (25 times the
background as reported two days ago) is due to Rn-222 products. This
conclusion is based on the following facts:

    a) I wiped my Toshiba TV next morning and reproduced the initially
       reported results.
    b) The half-life of the short-T component from the TV is 39 (+ or - 2)
       minutes. I can rationalize this along the Pb212 ->> Bi214 ->>Po214
       chain but I did not have time to confirm this quantitatively. (I do
       not believe that the 70 minutes decay (initially described by Mark
       as one to two hours) is consistent with the periods involved. I hope
       to be able to demonstrate this numerically, soon.
    c) And here is the most convincing argument. Last night I washed the TV
       screen with soapy water, let it dry for about two minutes and covered
       it with a wet towel to minimize contact with radioactive gases in the
       air. The screen was wiped this morning and I started countings about
       90 minutes ago. And what do I see? Ten times less radioactivity than
       on each of the previous days. The activity now is about twice the
       background and there is no indication that T=40 minutes is present.

What a wanderful activity for students. Ask them to "invent" a procedure to
test the hypothesis that "the radioactivity on TV screens is due to radon".
Ask them to compare radioactivity from different homes and tell them about
our debate. Share your experience with the rest of us. Too bad that my students
are no longer available; this is already an exam week for them. I will be
playing with this subject in the future.

                Ludwik Kowalski      kowalski@apollo.montclair.edu