Rn-222 progeny

[a.zapantis@qut.edu.au (Alex Zapantis)]

G'day all!

One of the researchers here plans to use  a Ra-226 source as a source of
Rn-222. (The source was manufactured specifically for this purpose) The
Rn-222 is pumped into a 3 m^3 chamber and is used as a tracer for aerosol
studies, the details of which I am not yet familiar. 

The maximum possible concentration of Rn-222 in the chamber will be 181kBq
per cubic metre (sorry about the SI units). The Rn-222 will remain in the
chamber for a few hours at most before it is vented to atmosphere. Some of
the studies will involve the introduction of aerosols such as tobacco smoke
into the chamber as well as the Rn-222. 

The chamber is manufactured predominantly from marine ply-wood with an epoxy
based coat.

I am determining the requirements for the venting system ie dilution
requirements, flow rates, location of dispersion point etc etc and would
appreciate any comments on the statements listed below, especially from
anyone who has experience with a similar situation.


1.    If no aerosol is present in the chamber, most of the Rn-222 progeny
will plate out on the internal walls of the chamber, however a significant
portion (50%, 25%??) will be pumped out with the Rn-222.

2.     If an aerosol is present in the chamber, almost all of the progeny
will become attached to the particulates of the aerosol and be pumped out
with the Rn-222.

Also, is there a commercially available filter suited to "catching" the
Rn-222 progeny (assume no aerosol) which may be in suspension in the chamber
to prevent it from being vented???     

All responses will be appreciated.

Regards



                        Alex Zapantis
                        Radiation Safety Officer                               
                        Queensland University of Technology          
                        Health & Safety Section                             
                        Locked Bag No.2
                        Red Hill Qld 4059
                        AUSTRALIA

                        Ph     : 61 7 864 3566
                        fax     : 61 7 864 3993
                        email  : a.zapantis@qut.edu.au