From: Matthew Ghio <ghio@chaos.bsu.edu>
Date: Tue, 23 Aug 94 09:56:40 PDT
To: cypherpunks@toad.com
Subject: Re: Nuclear Weapons Material
Message-ID: <199408231658.LAA11167@chaos.bsu.edu>
MIME-Version: 1.0
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pstemari@bismark.cbis.com (Paul J. Ste. Marie) wrote:
> Mark Terka wrote:
> > Not to mention the fact that without tritium, the "trigger" for nuclear
> > weapons (and extremely expensive and rare at $ 100m a gram) all you have
> > is a radioactive paperweight.
>
> The "trigger" isn't tritium.  Tritium (along with lithium 6) is used
> in fusion bombs.  A fission-only device, ala Hiroshima or Nagasaki,
> doesn't require any.
>
> The trigger in the center of the plutonium core is a neutron source,
> polonium if memory serves correctly.  Tritium is a beta emitter.

A neutron source is usually a light element with a high neutron/proton
ratio, coupled with an alpha emitter.  I believe the Nagasaki bomb used
beryllium-9.  An alpha particle impacting a beryllium nucleus will fuse
with it, forming carbon-12, and the binding energy will eject a neutron.
I think aluminum and a few other light elements will undergo similar
reactions to release neutrons in the presence of alpha particles.

Polonium is primarilly an alpha emitter.  It would work as part of a
neutron source, but it is not a particularily good choice because its
half-life is only 138.4 days (polonium-210).  This makes it expensive
to obtain, and impractical to store.