[ RadSafe ] Cs-137 beam calibrator output
JPreisig at aol.com
JPreisig at aol.com
Mon Sep 22 23:15:12 CDT 2014
Some of us theoretical/computational health physicists use MCNP, other
computer codes, and dose versus distance curves. also. See articles by
Hunt (England), Eisenhauer and Schwartz (USA) and more recent articles.
In a message dated 9/22/2014 10:51:43 P.M. Eastern Daylight Time,
doctorbill34 at gmail.com writes:
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.
It's not about dose, it's about trust.
On Mon, Sep 22, 2014 at 7:00 PM, clayton bradt <dutchbradt at gmail.com>
> My apologies if this duplicates an earlier post. Having received no
> notice for the previous one, I am re-sending from a different email
> 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
> along the beam center line was 0.2443 R/h on the same date. Comparing
> 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
> per Ci. I am surprised at such a large difference (27%) between the
> theoretical value and measurement. Should I be? I know that scatter
> 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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