From: "Peter Trei" <trei@process.com>
Date: Wed, 8 Oct 1997 22:37:36 +0800
To: cypherpunks@toad.com
Subject: Re: russia_1.html
Message-ID: <199710081351.GAA15050@toad.com>
MIME-Version: 1.0
Content-Type: text/plain



> From:          Jonathan Wienke <JonWienk@ix.netcom.com>
> At 09:37 AM 10/6/97 -0700, Bill Frantz wrote:
> >At 3:01 AM -0700 10/6/97, Peter Trei wrote:
> >>The plutonium cores of thermonuclear devices have a limited shelf
> >>life - he claimed 6 years, which jibes with what I've heard from
> >>other open sources. Fission products build up in the cores which
> >>can poison a chain reaction. Thus all Pu based devices need to have
> >>the cores periodically removed and replaced with new ones, while the
> >>old ones have to go through a non-trivial reprocessing stage to
> >>remove the fission products.
> >
> >I think this comment is in error.  Plutonium has a half life on the order
> >of 250,000 years, so very little decay products would build up in 6 years.
> >The tritium used in thermonuclear weapons has a much shorter half life, and
> >would need to be replaced about that often.
> 
> One of the decay products of tritium (half-life: 12.5 years) is Helium-3,
> which aggressively absorbs neutrons and poisons the fission reaction of the
> plutonium.  If one has access to more tritium, which is commercially
> available for about US $50,000 per gram, the existing tritium can be
> purified and combined with the new tritium to bring the bomb back to full
> power.  If someone has the resources to obtain the bomb in the first place,
> refreshing the tritium probably wouldn't be a major problem.
> 
> 
> Jonathan Wienke

I conceed that it may not be the Pu decay products that cause the
limited shelf life of thermonuclear weapons; I suspect that it may
be components of the 'pit', which produces the initial burst of 
neutrons to kick of the reaction (the pit is effectively a small
fission bomb). This 'pit' may contain tritium (pit design is a very
well guarded secret, and I've seen very little about it in the open
literature). 

> If someone has the resources to obtain the bomb in the first place,
> refreshing the tritium probably wouldn't be a major problem.

I disagree. A terrorist could obtain a bomb by being given it, 
stealing it, or buying it as a turnkey system. However, I suspect 
that anyone with the facilities to recondition one of these
weapons could also build one from scratch. 

I don't know if it's comforting or worrying knowing that these
devices degrade - any in the hands of terrorists have a limited
time that they are a threat, but that fact may pressure a terrorist
to 'use it or lose it'.

Peter Trei