AW: [ RadSafe ] surface emission rate,surface DPM from 27 pCi Tc-99

Franz Schönhofer franz.schoenhofer at
Sun Dec 16 12:43:05 CST 2007


I hardly can express my gratitute to you for putting this topic into

What Mr KOFF (Synebrychoff, finnish brewery) was distributing was only
bluntant nonsense. DPM of a source is a fixed value as well as pCi/source or
Bq/source and independent of whatever geometry. If he wants to have some
other definitions, he might declare them as "KOFF"-units and seek
international acknowledgement. 

What I am anyway surprised is that not hundreds of RADSAFErs got into the
discussion and would tell Mr. KOFF that his question was simply ridiculous
and after posting his really ridiculous explanations that also this was more
than ridiculous. 

I do not mind, if somebody posts some erronious postings (I have done that
myself, but I always apologized), but like in the case of Mr. KOFF I would
appreciate if his clarification would be done not to far into the future. 

Best regards,


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

-----Ursprüngliche Nachricht-----
Von: Glenn R. Marshall [mailto:GRMarshall at] 
Gesendet: Sonntag, 16. Dezember 2007 18:58
An: Geo>K0FF; radsafe at; Franz Schönhofer
Betreff: RE: [ RadSafe ] surface emission rate,surface DPM from 27 pCi Tc-99

Dpm is a measure of the amount of radioactivity present.  If there is 60 dpm
of radioactivity present on the surface of an object, then that is how much
radioactivity is there.  It's a fixed value and it's present whether
detected or not.  There is no such thing as 2-pi dpm of 4-pi dpm.  2-pi and
4-pi, in the case of radiation detection, refer to the emission rate of
radiation (in this case beta particles) due to the decay of radioactive
The premise for your argument is incorrect.  You should refer to NUREG 1507
or ISO 7503-1. 


Franz says:" Furthermore I would have hoped that Mr. KOFF knows the
difference between
dpm (disintegrations per minute) and cpm (counts per minute). Obviously he
does not. "

*Franz, DPM or disintegrations per minute can be 2-pi steradian, or 1/2 of a
sphere, or 4-pi steradian or both halves of a sphere.

DPM is determined by activity level multiplied by probability of emission
for each radiation component of a nuclide. CPM is COUNTS per minute, which
is derived as the product of source DPM, subtended angle, probe efficiency,
and deadtime correction. CPM also has other meanings. George

Franz says:" Having worked more than thirty years on the determination of
radionuclides I
can assure everybody, that there is no interest in "how many particles are
leaving the test disc, but the most important analytical question is, what
the efficiency (both chemical and counting) is in order to translate cpm
into dpm. Am I missing something? This is the task of radionuclide
determination since probably 100 years!!!! "

*Franz, yes you are missing the whole point of the measurement. Yes it does
have uses. George

Franz says:" I would not be surprised if you would still not understand how
silly your
question was and even more that you insist on your less than amateurish
opinion. I do not expect that you will refrain from those silly postings. I
do not hopte that you will bother RADSAFE in the future. "

*Franz, hope in one hand..............

I'm here to share what I can, but especially to learn. That is supossed to
be, at least in part, the charter of this chat board. George

Best regards,


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

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