AW: Time needed for Rn-222 daughters to reach equilibrium with theirparent?

["Franz Schoenhofer" <franz.schoenhofer@CHELLO.AT>]

-----Ursprüngliche Nachricht-----

Von: owner-radsafe@list.vanderbilt.edu

[mailto:owner-radsafe@list.vanderbilt.edu]Im Auftrag von Frey, Steven R.

Gesendet: Mittwoch, 14. Jänner 2004 20:23

An: RADSAFE (radsafe@list.vanderbilt.edu)

Betreff: Time needed for Rn-222 daughters to reach equilibrium with

theirparent?





Dear Radsafers -



How long does it take Radon-222 daughter products to reach equilibrium with

their parent,

assuming one starts with only Radon-222 gas (no daughters yet having begun

ingrowth)?



-------------------------------------------



Steve,



Provided that the parent nuclide is longer-lived than the daughters as a

rule of thumb more than 99% equilibrium will be reached after ten

half-lifes. I suppose you are looking at the  s h o r t -lived daughters of

Rn-222. The short-lived daughter with the longest half-life is Pb-214 with

26.8 minutes half-life, so the time required will be approximately 270

minutes. The system has to be closed and undisturbed.



Best regards,



Franz





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