Conversion: millirad/hr to uR/hr -Reply

[ABELQUIE@ORAU.GOV]

Andrew-

For many practical purposes it can be assumed that 1 R equals 1 rad -
this relationship is especially good if one is dealing with rads in tissue. 
The only other concern then is the SI conversion:  1000 micro per 1 milli,
whatever the quantity being measured.  Thus the straightforward
answer is 1 millirad/hr equals 1000 urad/h.  However, if you're interested
consider the following, somewhat more detailed answer: 

It can be shown that 1 Roentgen is roughly equal to 0.877 rads in air
(Turner 1986 p. 192).  It is important to note at this point that the unit
Roentgen is only defined for exposure in air.  The following relationship
may be used to relate the dose in air (Dair) to other media, such as tissue
(Dtissue):

D_{tissue}~=~D_{air}~{(æ_{en}/*)_{tissue}}over {(æ_{en}/*)_{air}}

where:
(æen /*)tissue  is the  mass energy absorption coefficient in tissue, and

(æen /*)air   is the  mass energy absorption coefficient in air.

This relationship between the dose in tissue to the dose in air can then
be established for a range of gamma energies.  The following table can
be constructed:

Gamma Energy   (æen /*)air 	 (æen /*)tissue    (æen/*)tissue/(æen /*)air
(keV)

100		0.0231		0.0252			1.091
200		0.0268		0.0297			1.108
400		0.0296		0.0325			1.098
600		0.0296		0.0326			1.101
1000		0.0280		0.0297			1.061
1500		0.0255		0.0281			1.101
2000		0.0234		0.0257			1.098