[ RadSafe ] Cs-137 beam calibrator output

[William Lipton]

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:
>
>
> I’ve 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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