Re: Bin Laden's attempts to acquire nuclear materials

From: Michael M. Butler (
Date: Fri Sep 14 2001 - 06:11:46 MDT

Eugene Leitl wrote:
> A modern nuclear device is a rather well designed artifact. It tends to
> minimize the fissible yield and maximizing the fusion yield, both for
> economical and cleanness reasons. To do so, it uses a minimal fission
> primer, which only goes off due to a highly symmetric core assembly, plus
> a highly timed neutron kickstarter pulse injected into the core. The
> timing sequence for the correct assemly is nontrivially encoded in a keyed
> black box. The people who handle the nuclear devices are not issued these
> key codes except shortly before that device will be used. Without it, a
> modern nuke is designed not to detonate.

Agree. Will add that most are also designed with a pit that is not detonable unless
tritium gas at pressure is present in the pit prior to compression. This tritium
boosting gets you more bang for your fissile mass, less fallout and a safeguard;
basically a triple weaponology win if you have the tech in the first place.

I speculate that this was the one remaining safeguard that was not present in the
famous case of the downed US warhead that had n-1 of its n (7? 8?) safeguards tripped.

As for the codes: word is that at least some KGB theater level officers had the go codes
for the manpack nukes the Spetsnaz were holding. How many? Who knows?

> It is much easier to purify plutonium from decayed nuclear ashes and make
> a low-yield dirty (if not salted) gun assembled device.

Umm, I think gun==U. As far as I recall Pu self-heats too much for a gun device to be
very manageable. All those different crystalline phases get weird fast. IIRC, even a
hemisphere of Pu gets too hot unless you are doing tricks with high compression and T boosting.

But I'm not absolutely sure about all Pu isotopes.
Absolutely agree that you can make weapons out of non-weapons-grade material.
"Plan C" is, of course, to just knavishly make a big mess with a subcritical flash + plume.
Probably works as a WOMT, if not a WOMD.

"Du musst...Amboss oder Hammer sein." 
  -- J. W. von Goethe, _Der Gross-Cophta, Act II_

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