[ RadSafe ] [Radsafe] equilibrium factors for thoron?

Harry Reynolds hreynolds at energysolutions.com
Wed Sep 9 09:26:26 CDT 2009

Try this link.


See paper MPM-B.4

Harry Reynolds
801-649-2219 Desk
801-349-9036 Cell 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Nick Tsurikov
Sent: Wednesday, September 09, 2009 1:21 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] [Radsafe] equilibrium factors for thoron?

Dear colleagues,

I am getting a bit lost...  We all know the equilibrium factors for
0.2 for outdoors and 0.4 for indoors, which work perfectly fine - at
in a first approximation for assessing the doses.
However, the same equilibrium factor for thoron (Rn-220) is quite a
(maybe just for me...). As there is more equipment now that provides a
direct measurement of radon and thoron concentrations (which is quite
convenient) I am having trouble finding any references to convert the
to dose.  Some rather interesting numbers were quoted to me last week -
example that the thoron equilibrium factor may be as low as 0.01, on the
other hand other people telling me that it may be up to 0.6-0.7.
It will be very much appreciated if you could point me out in the proper
direction - some regulatory documents, studies, whatever - that I can
use in
trying to compare the levels I am measuring with the limits that are in
places set up for 'equilibrium equivalent concentrations' - EEC.  The
regulators who wrote the document put there the values of 60 Bq for EEC
Rn-222 and 10 Bq/m3 for EEC of Rn-220, but are not sure themselves what
equilibrium factors were used; and your help will be very much

Kind regards
Nick Tsurikov
Western Australia
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