[ RadSafe ] Cs-137 beam calibrator output

[Sander Perle]

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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