[ RadSafe ] Measuring alphas with GM? Re: Survey MDAs vs. ScanMDAs

[Franz Schönhofer]

I can confirm this, though in the Arizonan desert I did not survey the cacti
for alpha-emitters, but rather the desert for cacti....

My experience was made during the Mururoa-Project of the IAEA, where I
checked on all the places where we took soil, coral, plants etc. the alpha-
and the beta-gamma contamination with large-area contamination monitors.
Though I was extremely careful not to touch any obstacles, especially corals
or tips of small plants the mylar-window was punctured within a few hours.
After having replaced it by a spare one and being even more cautious the
foil showed several hole within the next hour. I agree that such
alpha-monitors cannot be used in the environment, but probably on an even
surface like a table. Since the distance to the source is so crucial I would
not even in this ideal case trust any data expressed in Bq/cm2 (or
pCi/square inch...).

BTW, the titanium window of the xenon gas filled beta-gamma probe survived
much longer, but also this was punctured by the sharp end of a stem of
a shrub.

For the survey of plutonium-239 distribution we used thin NaI(Tl) crystals
to measure the gamma-rays of Am-241, which was associated with the Pu. The
radio was determined by radiochemical analysis of samples from soil or
corals.

Best regards,

Franz

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2006/5/12, John Jacobus <crispy_bird at yahoo.com>:
>
> Unless you put the material right up against the
> screen, alpha surveying in the field is pretty poor.
> During a training exercise, I had a friend who had
> problems surveying cacti in the desert.
>
>