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From: alcmist@ssc-vax.UUCP
Newsgroups: net.followup
Subject: Re: more on alternate energy sources (fusion)
Message-ID: <59@ssc-vax.UUCP>
Date: Mon, 20-Aug-84 15:56:40 EDT
Article-I.D.: ssc-vax.59
Posted: Mon Aug 20 15:56:40 1984
Date-Received: Tue, 21-Aug-84 07:13:07 EDT
References: <9681@gatech.UUCP>
Organization: Boeing Aerospace, Seattle
Lines: 52



The subject is drawbacks of fusion power, specifically damage to 
reactor walls from high-energy neutrons.

> From:     dmcnh!gts@sii
> Return-Path: 
> Date:     Fri, 10 Aug 84 12:20:17 edt
> Subject:  Re: alternate, hopefully safe, energy sources (fusion)
> References: <806@ihuxx.UUCP>, <9520@gatech.UUCP>
> 
> I thought that liquid lithium would flow along the inside of the walls
> of the fusion containment chamber.  Not only does this absorb the neutrons
> to prevent damage to the solid permanent walls, but in so doing, captures
> the heat of the reaction and can be used as a heat transfer medium.

The answer depends on the type of fusion reactor.  They come in two flavors.
A fusion reactor can hold its fuel in a more-or-less steady magnetic bottle,
which is called magnetic confinement, or it can hit a pellet of fuel with
high-energy lasers and hope a lot of energy is released before the pellet
flies apart.  That's called inertial confinement.

In either kind of reactor, the main reason for having lithium is to breed 
more fusion fuel.  When lithium is struck by neutrons from a fusion reaction,
it turns into tritium, which can be used in the fusion reaction.
(Tritium is an isotope of hydrogen ...)

A magnetic-confinement reactor has to work in a vacuum, otherwise junk gets
into the plasma and screws things up.  Lithium inside the reaction chamber
would evaporate and contaminate the plasma.  In a magnetic-confinement
reactor, the lithium would flow *outside* the wall of the reactor.

An inertial-confinement reactor doesn't have the problem of needing a
superclean vacuum.  It could use jets of liquid lithium to absorb neutrons,
breed fuel, transfer heat, and even absorb some of the shock from the
explosions of fuel pellets.

By the way, you really don't need tritium for a fusion reaction.  It's
just that the fusion between deuterium (naturally occurring and edible)
and tritium (man-made and radioactive) is the easiest to start.  Second
generation fusion plants would probably use a reaction that throws off
charged particles instead of neutrons.  Doing so is a lot harder but 
would allow direct conversion to electricity.  (There would also be
less radioactive material to handle).

Fred Wamsley   
-- 
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