[ RadSafe ] Cs-137 beam calibrator output

[Ted de Castro]

Which would result in making what should/could be a primary calibration 
source into a tertiary source.


On 9/23/2014 6:33 AM, Sander Perle wrote:
> I concur with Bill. The appropriate method would be to use a NIST traceable
> ion chamber and then TLDs or other passive device can be used to simply
> correlate and verify. Any passive or active dosimeter will have its own
> influence factors and associated uncertainty and should not be the primary
> method.
>
> Regards,
>
> Sandy
> Retired, Consultant
>
> From:  William Lipton <doctorbill34 at gmail.com>
> Reply-To:  "The International Radiation Protection (Health Physics) Mailing
> List" <radsafe at health.phys.iit.edu>
> Date:  Monday, September 22, 2014 at 7:51 PM
> To:  "The International Radiation Protection (Health Physics) Mailing List"
> <radsafe at health.phys.iit.edu>
> Subject:  Re: [ RadSafe ] Cs-137 beam calibrator output
>
> You can't rely on theoretical calcs; there are too many complicating
> factors.  You have to develop dose versus distance curves using NIST
> traceable ion chambers or similar instruments.  Maybe TLD's as part of a
> NVLAP certified system would work.
>
> Bill Lipton
> It's not about dose, it's about trust.
>
>
> On Mon, Sep 22, 2014 at 7:00 PM, clayton bradt <dutchbradt at gmail.com> wrote:
>
>>   My apologies if this duplicates an earlier post. Having received no bounce
>>   notice for the previous one, I am re-sending from a different email
>>   account.
>>
>>   ********
>>
>>   Original post:
>>
>>
>>   I¹ve been reviewing data for a beam calibrator containing a Cs-137 source
>>   with nominal activity 600 mCi on 1/18/2005.  The measured output at 1 meter
>>   along the beam center line was 0.2443 R/h on the same date.  Comparing that
>>   with the calculated exposure rate at 1meter from a 600 mCi point source I
>>   get 0.193 R/h, assuming a Gamma constant for Cs-137 of 0.322 R/h at 1 meter
>>   per Ci.   I am surprised at such a large difference (27%) between the
>>   theoretical value and measurement.  Should I be?  I know that scatter from
>>   the collimator will affect the actual exposure rate, but this much?
>>
>>
>>
>>   Any help from people with more experience with exposure rate calibrations
>>   on this list will be most appreciated.
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