Re: Choice of radiation units to use

[Janzow1@aol.com]

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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