[ RadSafe ] 600 years

[Stewart Farber]

For what it's worth, Carl Sagan's favorite number of a billion is wrong in this case. For 20 half lives, the decline of activity is y^x= 2^20 = 1.05 E6 not 1E9 ---
Bjorn's factor of an approximate million fold reduction in Cs-137 & Sr-90 in 20 half lives [600 years] is correct.

Stewart Farber, MS Public Health
Farber Medical Solutions, LLC
Bridgeport, CT 06604

[203] 441-8433 [office]
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--- On Mon, 9/27/10, Scott Davidson <bsdnuke at gmail.com> wrote:

> From: Scott Davidson <bsdnuke at gmail.com>
> Subject: Re: [ RadSafe ] 600 years
> To: "The International Radiation Protection (Health Physics) Mailing List" <radsafe at health.phys.iit.edu>
> Date: Monday, September 27, 2010, 11:29 PM
> A billion.
=============
> On Sep 27, 2010 10:30 PM, "Bjorn Cedervall" <bcradsafers at hotmail.com>
> wrote:
> >
> >
> > 600 years is about 20 half-lives of Cs-137 and Sr-90.
> This means that
> their radioactivity levels have fallen by a factor of 1
> million.
> >
> > Just a reflection.
> >
> > Bjorn Cedervall
> >
> 
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