Re: When does "rem" no longer apply?

[LIPTONW@detroitedison.com]

You wrote: 
 
Good day, 
> 
>Just came from a meeting where the question arose as to when "rem" (or 
>similar "effective" risk quantities) no longer applies. 
> 
>Any thoughts? 
> 
>Thank you. 
> 
>Yours, 
>John 
> 
>John F. Copeland, Ph.D. 
>Radiology, Beth Israel Deaconess Med. Center 
>Harvard Institutes of Medicine, Suite 147 
>4 Blackfan Circle, Boston, MA 02215 
>T: 617-667-0181, F: 617-975-5233 
>E:jcopelan@bidmc.harvard.edu 
> 
 
One source of guidance is 10 CFR 20.  Note that, in 10 CFR 20.1003, 
"Definitions":  
 
(1) "High radiation area means an area, acessible to individuals, in which 
radiation levels could result in an individual receiving a dose equivalent
in 
excess of ****0.1 rem (1 mSv)**** in 1 hour at 30 centimeters..." 
 
(2) "Very high radiation area means an area, accessible to individuals, in 
which radiation levels could result in an individual receiving an absorbed 
dose in excess of ****500 rads (5 grays)**** in 1 hour at 1 meter..."   
 
[emphasis is mine] 
 
Note that "high radiation area" is expressed in rems, while "very high 
radiation area" is expressed in rads.  Thus, the NRC considers the limits of 
the established quality factors to lie somewhere between 100 mrad/hr gamma
and 
500 rad/hr gamma. 
 
The opinions expressed are strictly mine. 
It's not about dose, it's about trust. 
 
Bill Lipton 
liptonw@detroitedison.com