AW: [ RadSafe ] Alpha to Beta Ratio Source Indication

Tue May 29 14:36:42 CDT 2007

Mike,

Gratulations, you are right on topic, as well as another RADSAFEr - sorry, I
have deleted the message already! 

I was considering to deliver a similar message, but being monitored on
RADSAFE I have decided not to react on this particular topic, because it
might be classified as "arrogant" by "certain" non-European RADSAFErs, as it
has been many times before. (Deliberate wording.) 

Now I dare to ask you and RADSAFE, why so many people want to solve the most
complicated radio-analytical problems by using the most simple and
unreliable measurement devices. Those questions on RADSAFE have surfaced
ever since I joined RADSAFE - which must have been at least ten years ago:
Doses from mixtures of many different radionuclides to be measured by using
the most simple GM counters, the (extremely difficult) determination of
surface contamination by just taking any (any!) swab, determination of NORM
by using dose-rate-meters etc. etc. Shouldn't one use the appropriate
instruments - even if they are expensive - to give the answer to a
surveillance programme?

I know since decades about the problems with those gross alpha or beta or
even gross alpha/beta measurements. They might work well if the measured
values are orders of magnitude lower than the "worst case". Especially the
question of radon (and thoron) progeny is a classic example, drinking water
analysis is another excellent one. Only today I checked the home page of the
Austrian Standardisation Institute to find several new proposals for the
accurate (!!!) determination of gross activities in drinking water. Is the
gross beta activity due to tritium or Sr-90, is the gross alpha activity due
to Ra-226 or even Po-210 or simply to whatever uranium? 

I agree with the original post, if the possible source of the activity is
very well known, then probably some calibration could be done - but I
personally do not know of any such case. 

Best regards and I really would appreciate to receive answers as to the
question, why people want to solve the most complicated analytical questions
with the least appropriate instruments.

Franz

Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna
AUSTRIA

-----Ursprüngliche Nachricht-----
Von: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] Im Auftrag
von Brennan, Mike (DOH)
Gesendet: Dienstag, 29. Mai 2007 18:44
An: radsafe at radlab.nl
Betreff: RE: [ RadSafe ] Alpha to Beta Ratio Source Indication

I can't think of a reason to believe that such a ratio exists.  There
are just too many factor.  For example, if you run a air sampler
collecting particulate on a filter, you will wind up with a lot of radon
daughter products on the filter.  When you first take the filter off the
sampler there will be a particular ratio of the various isotopes in the
decay chain (plus possibly other, unrelated isotopes from other
sources).  Some of the isotopes in the chain decay via alpha, some via
beta.  Over the next several hours the isotopes on the filter will
decay, total activity will decrease noticeably, and the ratio of alpha
to beta decays will change dramatically.  

Now, if in addition to a ratio you also could compare the results to
previously collected background results for the same media in the same
environment, you might well be able to say something, but I suspect that
it would mostly be a confirmation of what you already suspected. 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Goff, Tom
Sent: Tuesday, May 29, 2007 5:42 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Alpha to Beta Ratio Source Indication

Does anyone know of a basis for determining if the source of
radioactivity on a smear or air sample is natural, fission product or
transuranic based on the alpha to beta ratio.  

For example, if the ratio is greater than 3 then the source could be
Actinide; it the ratio is less than 0.5, the source could be fission
product; if the ratio is between then natural radioactivity is
indicated.

Does anyone know of a reference for these ratios?

Tom Goff
WIPP Radiological Services
505 234-8861
fax 505 234-6062
<mailto:Tom.Goff at WIPP.ws>
B452
P.O. Box 2078
Carlsbad, New Mexico 88221
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