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Re: I-129 in C-14 Sodium Acetate



Ralph NORTH wrote:
> 
> 
>      We have several sealed ampules of Sodium Acetate-1-14C (.5 mCi each).
>      There seems to be a small (nCi) amount of I-129 in each one. Any
>      explanations?

Ralph and Fellow Radsafers,

My first thought is "how did you measure the supposed I-129?" Probably
with a sodium iodide crystal detector I would guess.

C-14 has a 156 keV maximum beta energy and an average energy of about 50
keV. Even weak beta emitters will generate some Bremsstrahlung
radiation.  My guess is that the Bremsstrahlung radiation from the C-14
betas appear as a broad photon peak around 30 keV, thereby mimicking the
30 keV photopeak of I-129 (and 60 day half-life I-125 also).  Since the
resolution of NaI detectors is quite poor around 30 keV, it would not be
difficult to misinterpret a broad Bremsstrahlung continuum for a poor
resolution photopeak.

A good mystery, any other theories out there??

Cheers, Wes
-- 
Wesley R. Van Pelt, Ph.D., CIH, CHP                   KF2LG
President, Van Pelt Assoc., Inc.      vanpeltw@mail.idt.net
Consulting in radiological health and safety.
"TIME, its what keeps everything from happening at once."