[ RadSafe ] Testing bombs

Steven Dapra sjd at swcp.com
Mon Jun 30 19:21:13 CDT 2008

June 30


         Thank you for your explanation of the subtleties of a Pu bomb, and 
for recommending Serber's book.  I also appreciated your explanation of the 
distinctions between atomic and chemical explosions.

         I will look on Amazon for Serber's book.

Steven Dapra

At 10:52 AM 6/30/08 -0700, Dukelow, James S Jr wrote:

>Nobody has really answered Dapra's original question, which has some 
>contemporary relevance.
>The difference between the U-235 bomb and the Pu-239 bomb is that the 
>Pu-239 was contaminated with other isotopes of Pu that have significant 
>spontaneous fission rates.  If the process of assembling a critical mass 
>was "slow" (say, tens of milliseconds), there would be a significant 
>probability that the assembling critical mass would be "pre-ignited" by 
>stray neutrons from the spontaneous fissions, leading to a lower yield -- 
>a "fizzle".  The answer was to used carefully designed explosive charges 
>to assemble the critical mass very quickly.  Until Trinity, the implosion 
>design was theoretical and the test was need to give confidence that the 
>weapon would work.
>All of this is very nicely described in The Los Alamos Primer, by Robert 
>Serber.  It is the annotated notes of the lectures that Serber gave to 
>physicists and other arriving at Los Alamos to participate in the 
>Manhattan Project.  The notes were published in 1992 and are currently 
>available from Amazon.
>This problem did not exist with U-235 and the physicists were quite 
>confident it would work the first time.
>The current relevance is that Iran, and earlier, North Korea is/were using 
>both plutonium production and uranium enrichment to pursue nuclear weapon 
>capability.  The weaponization issues remain with plutonium weapons and 
>uranium weapons remain simple to implement once sufficient fissile 
>material is available (although "deliverable" weapons may be more of an issue).
>Dowell's linguistic distinction between nuclear (fission and fusion) 
>explosions and atomic/chemical explosions is not standard usage, but is 
>reasonable.  The nuclear weapons involve the release of the nuclear 
>binding energy of the atomic nucleus, while chemical explosions release 
>the chemical binding energy of the electron orbitals.
>Hanford's weapons mission is over and it is probably not to hard to 
>arrange tours of most of the facilities, although I haven't tried to do it.
>Best regards.
>Jim Dukelow
>Pacific Northwest National Laboratory
>Richland, WA
>jim.dukelow at pnl.gov
>These comments are mine and have not been reviewed and/or approved by my 
>management or by the U.S. Department of Energy.
>-----Original Message-----
>From: radsafe-bounces at radlab.nl on behalf of Steven Dapra
>Sent: Sat 6/28/2008 8:49 AM
>To: radsafe at radlab.nl
>Subject: [ RadSafe ] Testing bombs
>June 28, 2008
>         From time to time I have read that one of the Hiroshima and 
> Nagasaki bombs
>had to be tested before it was used, and that one did not --- that the
>engineers were so certain the latter bomb would explode that they didn't
>bother testing it.  I also read recently that hydrogen bombs must be
>tested.  Of these three types of bombs, which ones must be tested, and
>why?  For the one that did not have to be tested, why not?  (I don't have
>any bombs I want to test, I am merely curious.)
>Steven Dapra
>sjd at swcp.com

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