[ExI] cost of SBSP and thorium

[John Clark]

On Mon, Aug 20, 2012 at 1:08 PM, Charlie Stross <charlie.stross at gmail.com>wrote:

>> Modern H-bombs may use a very small about of tritium in their neutron
>> nitiators but the vast majority is bred in a very small fraction of a
>> second from Lithium Deuteride. It was originally thought that only the rare
>> isotope Lithium-6 would work for this purpose but it was later found that
>> the common isotope Lithium-7 would work almost as well. That's why the
>> first H-bomb test that used Lithium Deuteride, the Castle Bravo test
>> in1954, was expected to produce a blast of 4 megatons but ended up
>> producing 15, it killed several Japanese fishermen who were well outside
>> the official danger area.
>
>

> If that's the crew of the "Lucky Dragon", weren't they caught in the
> fallout plume rather than directly killed by the heat flash/blast/prompt
> radiation?
>

Yes. The unexpected excess of tritium caused more fusion reactions and thus
more extremely high energy neutrons.  Neutrons that move this fast will
cause even the hard (but not impossible) to fission U238 in the tamper to
fission. Actually in a H-bomb about 70% of the energy does not come
directly from the fusion reaction but from the fission of common hard to
fission U238 in the tamper from very fast neutrons produced by fusion; most
of the radioactive fallout also comes from the fission of that U238 by
those very very fast neutrons, and the fallout was what killed the
fishermen.

  John K Clark
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