RE: Color TV screens as radon daughter collectors

[alstonchris@netscape.net]

Well, *radon's* half-life is 3.8 d.  But, here are its first four (4) daughters (of more than 0.1% abundance), with half-lives parenthesized: Po-218 (3 m), Pb-214 (27 m), Bi-214 (20 m), Po-214 (164 us). Pb-210 is next, but, given its 22 y half-life, there's clearly not a great deal of time for ingrowth, in this context.



Now, *thoron's* half-life is 56 s.  So, most of the time it's not a problem, because it decays before it can escape the soil, to spread daughters.  But, the daughters', and half-lives, are: Po-216 (0.15 s), Pb-212 (10.6 h), Bi-212 (61 m), Po-212 (305 ns), Tl-208 (3.1 m), Pb-208 (stable).  So, you see some weird ingrowth curves, and counts from thoron daughters will actually increase, in the short term after sampling, instead of decreasing, like those of radon daughters.



Note: all the decay data above are from the 3rd edition of the Rad Health Handbook.



Cheers

cja





Jeffries Cameron <jeffriesc@epa.nsw.gov.au> wrote:

>Actually you have it round the wrong way. The radon decay series is longer

>lived (approx 4 days) and thoron is the shorter lived decay series.











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