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From: ran@ho95e.UUCP (RANeinast)
Newsgroups: net.politics,net.sci
Subject: Re: Small Nuclear Bombs (Californium half-life)
Message-ID: <685@ho95e.UUCP>
Date: Fri, 16-May-86 10:50:44 EDT
Article-I.D.: ho95e.685
Posted: Fri May 16 10:50:44 1986
Date-Received: Sun, 18-May-86 03:12:12 EDT
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Organization: AT&T Bell Labs, Holmdel NJ
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>In article <684@riccb.UUCP> jmc@riccb.UUCP (Jeff McQuinn ) writes:
>>>     I was talking to an ex-LLL physicist once who told me that there 
>>> is an isotope of Californium with a *very small* critical mass (a few
>>> grams, I think it was). This opened the theoretical possibility of a
>>> hand grenade sized nuclear weapon.
>>
>>Californium, isn't that one of those wonderful man-made elements whose shelf
>>life can be measured in microseconds? No wonder it's "theoretically" possible.
>
>The theoretical possibility is not for a californium bomb--we're mellow
>remember--but for an xx-ium bomb where xx-ium has *very small* critical
>
>ucbvax!brahms!weemba	Matthew P Wiener/UCB Math Dept/Berkeley CA 94720


Californium will work just fine, thank you.  I just looked it up
in the CRC handbook.  (Doesn't anybody uses references anymore?  Oh, yeah.
I forgot.  This is netnews.)


Just for comparisons sake, U-235 has a thermal neutron cross-section for fission
of 579.5 barns, and Pu-239's is 742.4 barns.  There are two isotopes
of Californium with large thermal neutron cross-sections for fission,
Cf-249 at 1735 barns and Cf-251 at 4000 (!) barns.  With such a large
cross-section, I suspect Cf-251 would make a quite small device.
And the half-lives?  Cf-249 has a half-live of 360 years, and Cf-251's
is 800 years, plenty long enough.

By the way, the quoted error bars on the Cf-251 were quite large
(about 25%).  This suggests to me that either they haven't made enough
of the stuff to measure it properly, or (more likely), the exact results
are classified (because they're using the stuff to make hand grenade
sized nuclear weapons).
-- 

". . . and shun the frumious Bandersnatch."
Robert Neinast (ihnp4!ho95c!ran)
AT&T-Bell Labs