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RE: Conversion of Exposure to Dose
This is true. However, in many (most? all?) case the 1 R ~ 1 rad ~ 1 rem ~
10 mSv approximation is adequate for radiation protection purposes. For more
accurate effective dose or effective dose equivalent estimates, a more
sophisticated approach is needed. I've used the organ dose tables from FGR
13, "External Exposure to Radionuclides in Air, Water, and Soil,"
(EPA402R93081) to estimate roentgen to rem (effective dose equivalent) when
necessary.
Jerry Falo
How beautiful it is to do nothing, and then rest afterwards. - Spanish
proverb
The statements herein are entirely the fault of the author and in no way
should be interpreted as official statements of any person or organization
unless otherwise noted.
Gerald A. Falo, Ph.D., CHP
Henry M Jackson Foundation Professional Associate
United States Army Center for Health Promotion and Preventive Medicine
Health Physics Program
gerald.falo@apg.amedd.army.mil
-----Original Message-----
From: Leo M. Lowe - SENES Consultants Limited [mailto:llowe@senes.on.ca]
Sent: Wednesday, May 29, 2002 6:24 PM
To: radsafe@list.vanderbilt.edu
Subject: Conversion of Exposure to Dose
In recent messages, some people in converting from the "old" units to SI
units assume a one-to-one relationship between exposure in R and rem (or
0.01 Sv). For example, an instrument reading an exposure rate of 100 mR/h
is stated as being the same as 100 mrem/h or 1 mSv/h - this is incorrect.
The conversion depends on the gamma energy and irradiation geometry because
of self-shielding by the body. For example, for gamma radiation from
uranium-series radionuclides in the ground, the relationship is
approximately 100 mR/h = 60 mrem/h = 0.6 mSv/h, where the mrem and
mSv units are effective whole body doses i.e. the doses that are usually
cited in regulated radiation limits.
Survey meters that read in units of mrem/h or mSv/h often don't make this
distinction. In fact, they can't for all circumstances. At best, they
can give tissue equivalent dose rate (e.g. plastic detectors), but not the
effective whole body dose.
Leo M. Lowe, Ph.D.
Principal, Senior Health and
Environmental Physicist
SENES Consultants Limited
121 Granton Drive, Unit 12
Richmond Hill, Ontario
Canada L4B 3N4
Tel: (905) 764-9380
Fax: (905) 764-9386
e-mail: llowe@senes.on.ca
WWW: www.senes.on.ca
This transmission is intended only for the addressee and may contain
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