Re: Fusion Power

From: Lawrence Johnston (
Date: Fri Jun 06 2003 - 11:04:13 EDT

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    Hi, Iain -

    I'm happy to get info from people who have worked in the fusion

    In your response below, you assume that Li^7 is stable, and is
    the fuel for more tritiuim. But, as George Murphy and the
    original Hutchinson article pointed out, the stable isotope is
    Li^6. If it were Li^7, you might indeed get more neutrons in the
    output, and have a Litium chain reaction going to produce
    tritium. But the reaction

    Li^6 + N -> Li^7 -> He^4 + H^3 is the one George

    Li^7 is extremely unstable, with a half-life of maybe 10^-12
    seconds. *

     So what we need then is an estimate of the efficiency of this
    process for regenerating tritium, taking into account the losses
    of neutrons in the reactor vessel, and the cross section of Li^6
    for the above reaction. It must be much less than 100%, leaving
    the need for some outside source for most of the tritium, such as
    fission reactors.
    Thanks, Iain.

    Best, Larry Johnston
    *In the early days of investigating this reaction, I remember
    that investigators loaded nuclear photographic emulsion plates
    with Lithium, (Li^6) and exposed them to particle beams. They
    always got "hammer tracks", the handle of the hammer being the
    incident charged particle, and the hammer head being the He ion
    and the T ion, going in almost opposite directions. There was no
    measurable space between the handle and the head, indicating that
    the life of the compound nucleus was very short.

    Date sent: Thu, 05 Jun 2003 21:41:20 +0100
    From: Iain Strachan <>
    Subject: Re: Fusion Power
    To: Lawrence Johnston <>,

    > Hi, Lawrence,
    > I worked for some time at the UKAEA (United Kingdon Atomic Energy Authority)
    > Culham laboratory, which was the main UK centre for Fusion research, and
    > host site to the large scale JET (Joint European Torus) experiment. Though
    > JET did not address the issue of getting large amounts of Tritium, the
    > proposals for the next torus (NET) did do studies on this.
    > The basic idea is that fresh supplies of Tritium are bred from a blanket of
    > Lithium 7 which would be contained in the walls of the reactor vessel. I
    > can't remember the exact details but the idea is that a neutron + Lithium 7
    > nucleus causes it to split into an alpha particle and a Tritium nucleus
    > (plus, I suppose, another neutron). The neutrons come from the DT reaction
    > as a byproduct.
    > Lithium is of course a highly abundant element.
    > I believe there are fearsome technology problems to crack to get a workable
    > system; tritium containment, cooling and so forth.
    > Hope that answers your question.
    > Best,
    > Iain.
    > ----- Original Message -----
    > From: "Lawrence Johnston" <>
    > To: <>
    > Sent: Sunday, June 01, 2003 1:53 AM
    > Subject: Fusion Power
    > > Dear fellow ASA-ers:
    > >
    > > In the June issue of Perspectives there is a nice article by Ian
    > > Hutchinson, about his work on fusion power, in magnetic
    > > confinement reactors.
    > >
    > > This reminds me of a question that keeps coming back to me so I
    > > hope there is someone on our List who can help me understand why
    > > there is a hope that fusion power will someday be a practical
    > > energy source.
    > >
    > > Hutchinson talks about the D-T (Deuterium-Tritium)reaction as
    > > being the fuel. I can see where there is a natural source of
    > > Deuterium in heavy water. But where can you find an economical
    > > source of Tritium? My understanding is that tritium is made in
    > > fission reactors, so there is enough to do experiments with. But
    > > where would one get commercially important amounts of Tritium?
    > >
    > > I hope someone is lurking who has some knowledge of this field.
    > >
    > > May God richly bless, Larry Johnston
    > >
    > >
    > > =======================================================
    > > Lawrence H. Johnston home: 917 E. 8th st.
    > > professor of physics, emeritus Moscow, Id 83843
    > > University of Idaho (208) 882-2765
    > > Fellow of the American Physical Society
    > > =========
    > >

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