[ RadSafe ] Re: U-238 spontaneous fission

Bob Cherry bobcherry at satx.rr.com
Wed Jun 18 13:58:25 CDT 2008

Not only trivial: it is literally un-measurable by the most sophisticated

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf
Of Otto G. Raabe
Sent: Wednesday, June 18, 2008 1:25 PM
To: Peter Bossew; radsafe at radlab.nl
Cc: Brennan, Mike (DOH)
Subject: Re: [ RadSafe ] Re:U-238 spontaneous fission

At 10:25 AM 6/18/2008, Peter Bossew wrote:
>A short calculation:
>The effective  SF decay rate of 238U is lambda=2.678e-24 s-1.
>1 mol = 238 g of 238U contains A=6e23 atoms with an activity of
>lambda*A=1.6 SF decays per second
>I did not find a nu value for spontaneous fission of 238U; for fast 
>fission it is 2.819 (http://www-nds.iaea.org/sgnucdat/a6.htm ), which 
>is a conservative estimate for SF (I think). Thus we find
>1.6*2.819=4.51 n/s per mol due to SF, or 0.019 n/s = 68 n/h per g 238U. 
>For 1 ug this is about 1 neutron every 609 days. Wow.
>68 agrees well with the quoted number 59.5.
Obviously a trivial exposure. If someone is really concerned about neutron
exposures, there is a much higher exposure to neutrons in a transcontinental
flight in a commercial airlplane.


Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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