[ RadSafe ] cesium 137 check source rate

[Geo>K0FF]

Good John, did you remember to divide the answer by two to take into account 
the 2 Pi steradian distribution due to probe shape?

George
----- Original Message ----- 
From: "Dixon, John E. (CDC/ONDIEH/NCEH)" <gyf7 at cdc.gov>
To: "The International Radiation Protection (Health Physics) MailingList" 
<radsafe at health.phys.iit.edu>
Sent: Wednesday, August 18, 2010 9:40 AM
Subject: Re: [ RadSafe ] cesium 137 check source rate


>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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