[ RadSafe ] definition of Rad (UNCLASSIFIED)

Falo, Gerald A Dr KADIX Jerry.Falo at us.army.mil
Wed Oct 3 13:46:06 CDT 2007

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Caveats: NONE


I've not seen of the Wikipedia definition regarding the rad.  Most
everything I've seen implies that because 1 roentgen (for "conventional
x-rays") is equal to about 97.7 ergs per gram (or some other value close
to 100 ergs per gram), that the definition of the rad was chosen to be
100 ergs per gram.  See, for example, Herb Parker's article in the
Indian Journal of Radiology in 1956, reprinted in "Herbert M. Parker,
Publications and Other Contributions to Radiological and Health
Physics," edited by Kathren, Baalman, and Bair, 1986.

The origin of the name "rad" can be found at


The statements and opinions expressed herein are my responsibility; no
one else (certainly not my employer) is responsible, but I still reserve
the right to make mistakes.
Don't panic! - Douglas Adams in "The Hitchhiker's Guide to the Galaxy"
Gerald A. Falo, Ph.D., CHP
Kadix Systems 
U.S. Army Center for Health Promotion and Preventive Medicine - Health
Physics Program
jerry.falo at us.army.mil
DSN: 584-4852

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Kai Kaletsch
Sent: Tuesday, October 02, 2007 12:11 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] definition of Rad


According to the Wikipedia entry for 'Rad', it was defined from 1918 to
1953 as the unit of X-ray dose required to kill a mouse. 1) I never
heard this definition before and 2) This seems like a very low dose for
killing anything.

This is somewhat before my time and I normally use SI units. Is the
Wikipedia statement correct?


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