Re: Re[2]: Radon Question from Occ-Med-Env

[Schoenhofer <schoenho@via.at>]

At 11:40 1996-07-02 -0500, you wrote:
>There may be some efficacy to the use of charcoal cartridge breathers for
>radon work.  Charcoal (especially at lowered temperatures) exhibits a
>certain affinity for noble gases, characterized by dynamic absorption
>coefficients corresponding to an effective delay in transit, a feature of
>charcoal beds used in offgas treatment systems for BWR steam jet air ejector
>exhaust to reduce xenon and krypton species prior to stack release.  The
>effect appears to be greater for larger atomic number, and could be
>significant at normal breathing rates for decay of radon to daughters which
>are more effectively filtered.
>
>Don't ask me for the corresponding data for radon, but I would be surprised
>if these measurements had not been performed in conjunction with research on
>sampling or treatment/remediation.
>
>Bob Hearn
>rah@america.net
>770-993-3927
>============================================================================
("radon" means in this message Rn-222)

Since the original question contains no information about the circumstances
the workers work in and why the radon is present in this concentration, it
is difficult to judge the situation. 

I have expressed my opinion in my reply to Ccja, that a dose close to zero
has to be expected, because the air containing radon entering the mask will
be expelled so fast that there is no time for the build up of radon daughters. 

Nevertheless it is known since the beginning of the century that charcoal is
even at room temperature an excellent adsorbens for radon. It was even used
to collect radon from radium and then desorb it to produce radon containing
water and medicines, which were believed to be healthy. In nuclear power
plants charcoal beds are used for Xe and Kr removal, but also to slow down
the migration of iodine isotopes. I-131 with its 8 days half life is slowed
down so much, that no I-131 is released - which gives some idea of the
efficient adsorption for iodine.

The adsorption of radon on charcoal is even used successfully in the
determination of radon concentrations in air. There are cartridges of
activated charcoal commercially available which are exposed to the air and
both air and radon diffuse into the cartridge, where radon is adsorbed. The
determination of the adsorbed radon may be done by gamma spectrometry or
with liquid scintillation spectrometry. We prefer and use the latter method
in my laboratory because the high efficiency of liquid scintillation
spectrometry for alpha particles (close to 100%) and we have measured now
more than 10 000 samples. This gives you an idea about the well established
technique of adsorbing radon on charcoal.

I conclude that charcoal should be efficient, but of course I donīt have the
information, how this workds when radon is sucked through and not slowly
diffuses into the filter.

Finally I have to mention that an radon concentration of 3 000 Bq/m3 is
nothing so unusual in living areas in Austria, Germany, Finland, Sweden,
Norway ..... I would be interested to know about the working place. Usually
high radon concentrations are mitigated to reduce them and it is unusual to
do it the other way round - namely to let the workers use protective gear,
which usually is very uncomfortable and has a negative impact on the work
performed.

Franz Schoenhofer
Federal Institute for Food Control and Research
Radiochemistry
Vienna, Austria
Schoenhofer
Habichergasse 31/7
A-1160 Wien
Tel./Fax:	+43-1-4955308
Tel.:		+43-664-3380333
e-mail:		schoenho@via.at