RE: Choice of radiation units to use

["Weiner, Ruth" <rfweine@sandia.gov>]

OK more from me.  There is, amazingly enough, a connection between the "SI
units" thread and the "stupid question" thread (or at least I think there
is).  Units are fundamental to solving problems in science (remember
dimensional analysis?).  Why did we never use (and never even think of
using) pints, quarts, etc in the chemistry lab, even though they were
initially much more "familiar" than liters?  Because we had to solve
problems in a single system -- the mks system, as it happens. The connection
to the "stupid question" thread?  Understanding units is so fundamental to
understanding science and the "language" of science that if one doesn't know
a unit conversion, either  working it out or looking it up is an experience
of educating oneself.  When I don't know the meaning of an English word, I
look it up in a dictionary -- I don't usually just ask, because by looking
it up I really learn it and don't forget it.  This is not a question of
appearing stupid, but a question of genuinely increasing one's store of
important knowledge.

I cannot see where historical units of radioactivity would be any more
familiar, except to a long-term professional in the field, than SI units,
and a long-term professional ought to be professional enough that
familiarity, whatever that is, shouldn't matter.  Certainly rems were not as
familiar to any of my students as quarts, so if going  to metric volume
units poses no problem, why should going to SI units pose a problem?


Clearly only my own opinion.

Ruth F. Weiner, Ph. D.
Sandia National Laboratories 
MS 0718, POB 5800
Albuquerque, NM 87185-0718
505-844-4791; fax 505-844-0244
rfweine@sandia.gov


-----Original Message-----
From: Janzow1@aol.com [mailto:Janzow1@aol.com]
Sent: Wednesday, September 08, 1999 8:50 PM
To: Multiple recipients of list
Subject: Re: Choice of radiation units to use


Hello:
     The proper choice of units depends upon the circumstances of use of the

units.  No unit or system of units is intrinsically "better" than any other.
     1.  The units to be used in a particular message or writing should be 
selected  for best understanding by those to whom the message or writing is 
directed.  When talking to radiation workers in my facility (some of whom 
have been such for over 30 years) , I use traditional US units.  Were I to 
tell such a person that a particular task will give them one sievert, the 
most likely response would be "OK" and the person would go off to do the
task 
unless physically restrained.  But if I tell the same person that the task 
will give him 100 Rem, the response will be much different, and very strong.
      2.   Some facilities have instruments which read in "US" units and 
which have been in use for many years.  Calibration histories, stability 
histories, reliability histories, failure-mode histories, etc. are available

for these units.  Yes, the instruments could be replaced with others reading

in "SI" units, but only at the cost of loss of knowledge of how the 
instruments respond, and thereby a loss of confidence in them.
       3.   The use of certain units is required by US and international
law, 
regulations, and/or standards.  Example:  The "Transport Index" required to 
be marked on all radioactive material shipping packages and on the related 
shipping documents.  The  Transport Index is defined by US, IAEA, ICAO, etc.

regulations as the highest dose rate in millirem per hour at one meter from 
any part of the package surface.  Yes, instruments reading in "SI" units can

be used to measure the Transport Index.  I prefer instruments reading in 
mRem/hr for this use as this elimininates the possibility of unit conversion

errors in determing whether the package is shippable, and in informing 
handlers of the package of radiation levels near it.
        Numerous other examples of use-related unit choices could be cited.
               
              Ed Janzow
                janzow1@aol.com
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