[ RadSafe ] cesium 137 check source rate

[Dixon, John E. (CDC/ONDIEH/NCEH)]

I agree George. The instrument indication dose rate from this source is
very dependent upon the probe used. A Geiger counter could use several
different probe types. For some probes (those without windows), the beta
particles will not be an issue. I simply used physics in my response
(Bremsstrahlung included). :-)

Regards,
John Dixon

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Geo>K0FF
Sent: Wednesday, August 18, 2010 10:25 AM
To: The International Radiation Protection (Health Physics) MailingList
Subject: Re: [ RadSafe ] cesium 137 check source rate

It should be noted that Cs-137 is a beta emitter and the beta component
will 
interfere with
the gamma component from the daughter product, Ba-137m, unless a beta
shield 
is used. Also the 32 keV
component can over respond as will the X-Rays from Bremsstrahlung from
the 
betas.

Secondly, since the source is small compared to the size of the probe,
the 
geometry is inadequate
for making a real mR/H measurement.

To do so would require a source strong enough to be placed 10 times the 
major dimension of the
probe away from the probe.

Bottom line is that any reading will depend on the size and construction
of 
the probe and the
distance to the source.


George Dowell
GEOelectronics
New London Nucleonics Lab


----- Original Message ----- 
From: "Dixon, John E. (CDC/ONDIEH/NCEH)" <gyf7 at cdc.gov>
To: <radsafe at health.phys.iit.edu>
Sent: Wednesday, August 18, 2010 7:06 AM
Subject: Re: [ RadSafe ] cesium 137 check source rate


> Harley,
> I did a quick calculation and found the source should emit about 32
> mr/hr (gamma) on its surface. This is a small isotropic source and the
> dose rate will drop very quickly. If the source was shipped in the US
by
> US mail,  the package (not the source) contact dose rate should have
> been less than 0.5 mr/hr.  Hope this helps.
>
> Regards,
> John Dixon
>
> -----Original Message-----
> From: radsafe-bounces at health.phys.iit.edu
> [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Harley Vance
> Sent: Wednesday, August 18, 2010 4:22 AM
> To: radsafe at health.phys.iit.edu
> Subject: [ RadSafe ] cesium 137 check source rate
>
> I just got a cesium 10 microcurie test source in the mail, and I
haven't
> gotten my geiger counter yet.
> My question is, what is the approximate rate of radiation at the
surface
> of the disc?
>
> It is blue and I believe it is encased in some kind of epoxy.
>
> Thanks!
>
>
>
>
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