From: jcliu@four-lab4.Berkeley.EDU (James C. Liu)
Newsgroups: soc.culture.japan
Subject: Re: Fusion (was RE:  Plutonium)
Date: 20 Nov 1992 22:42:55 GMT
Organization: UC Berkeley Dept. of Nuclear Engineering
NNTP-Posting-Host: four-lab4.berkeley.edu
Keywords: cold fusion?

In article <1992Nov19.164359.2208@island.COM> fester@island.COM 
(Mike Fester) writes:

>Just curious here, but what "present theories" would need to be modified to 
>account for cold fusion? As I understand it, to get to suitable nuclei to fuse,
>you need to get them into a certain close proximity for a certain minimum time.
>For atoms, (eg, H or D) the first problem is overcoming electron-electron
>repulsion. Assuming that you are operating on a catalytic surface, the 
>electrons can be effectively stripped off. You are now left with nuclear 
>repulsions. This can be in part masked by the metallic catalyst. The questions,
>as I understand it, are then a) what is the critical minimum distance for 
>fusion? b) can catalytic surfaces be sufficient to bring appropriate nuclei
>to within this critical distance? After that, of course, there's a practical
>question of whether or not this can be done on a larger scale, but if the 
>first two, and perhaps other, questions can be answered, this is a matter of
>engineering. 
>
>So, if the problem is NOT as I describe it above, what am I missing here?
>
>Mike

In materials thermo, there would probably major upheaval in the theory
of catalysts.  From my very limited knowledge, all catalyzing reactions
are chemical in nature.  Masking Coulomb forces in the lattice is
something I have heard of, but it again applies to the chemistry of the
material and never nuclear physics.  Nuclear reactions occur on length scales
orders of magnitude smaller than chemical reactions.

In terms of physics, we'd have to rethink the idea of short and long
range forces.  The idea has been that nuclear forces act only when the
proximity of nuclei is on order of the "apparent" nuclear cross
section.

As for "confinement" sufficient for fusion, the concept is often
misrepresented by many teachers and textbooks which give the idea that
one only needs to confine the nuclei together sufficiently long enough
in close proximity and fusion will occur.  This might give the
impression that you can hold two deuterium atoms one Angstrom (10e-10 m)
apart in the lattice of Palladium and if we wait long enough, fusion
will take place.  However, this gives the impression that the
probability distribution wave function (which determines the cross
section) for the deuterium nucleus is infinitely large or almost there
(because the electron distribution wave function is hecka bigger than the
nuclear one) but in our experiences, the typical crossection is much
smaller.  If we think of the electron cloud as a stadium, the football at
the 50 yard line is about the relative size difference between the electron
x-section and the nuclear x-section.  The actual nucleus is smaller than
the football, but the zone of influence is still going to be the size of
the football.  From this picture, then we can see that two footballs set
a kilometer apart aren't going to interact even if you held them there
for infinity.

You kinda hit the nail on the head when you posed questions a) and b).
The mininum distance required for the fusion reaction is on order of
10e-14 meters.  The lattice of Palladium provides interstitial sites at
distances of 10e-10 meters.  Four orders of magnitude too big.  Lonely
deuterons want to meet other lonely deuterons, but, their stuck on
opposite sides of the world.  They never meet.  They never fuse into
marital bliss. :-)  As for practicality of "cold fusion."  It's not just
Engineering.  We would have to examine the efficiency of the means of
production.  What temperatures are we talking about?  What energy
densities?  To be practical, we must examine things like the limitations
set by the Carnot efficiency of converting heating into useful work.

Fusion leaves definite radiation trails and produces a known quantity of
heat.  Most of the experiments tried after the Utah announcement failed
to produce anything.  A very few managed to produce either heat or some small
amount fo radiation.  Fleischmann and Ponns could not reproduce their
results on demand, even after $5 Million and a year.  I'm skeptical
because I believe that the majority of scientists are competent and
doing it correctly and I believe also in reproducibility.

Jaa, James

>-- 
>Disclaimer - I'm only doing what the little voices tell me to do. 

My disclaimer:  I'm a heat transfer, fluid mechanics dude;  Nuclear
Physics?  What's that?
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