Re: Nuclear heater for Expeditions

Dan Clemmensen (
Thu, 08 Jan 1998 22:33:16 -0500

Hara Ra wrote:
> Dan Clemmensen wrote:
> [SNIP nanotech-built "mister fusion"]
> I doubt that efficient tiny reactors can be built. There are two
> possibilities, one being cold fusion (which seems to be doubtful at the
> moment) and the other is based on sonoluminescence (SL). SL is still a
> macroscopic process but I could imagine a SL reactor in the kilogram
> size range.
nanotech is not magic. As 'gene says, it may not even be feasible. My
guessitmate is that is feasible. The requirement for fusion is that
atoms must slam into each other fast enough. The requirement for
useful fusion is "engineering breakeven": The process must emit
more useful energy with no external input. In the particular
application we're discussing, the useful energy is low-intensity
heat, which is the easiest goal to reach.

It's not proven that SL is blackbody rediation and therefore
indicative of near-fusion conditions, and the phenomenon is
not well enough understood to find a useful set of conditions
whereby you can extract useful energy: currently, SL is observed
only at temperatured near the freezing point of water. Don't count
on SL for micro-fusion.

I envision an D-D fusion reactor based on a form of inertial-confinement
fusion, using a truly tiny holraum and starting in an environment with
very high static pressure. The environment is the center of a set of
diamondoid spheres, each of which contributes a megapascal or so of
pressure differential. The D-D reaction emits no primary neutrons.
The innermost sphere brings the interior static pressure up to the
highest level that remains consistent with diamondiod nanotech and
diamondoid compressive and tensile strength. The nanotech machinery
contained within the inner shell then delivers a transient implosive
pulse to the holraum (mechanically, or with lasers, or with explosives)
to cause fusion. This geherates a lot of heat, raising the temperature
of th interior. The reactor uses the thermal gradient from inside to
outside to capture the energy neeeded to drive the next pulse.

> OTOH, using nanotech for waste disposal, including body waste, for full
> oxidation would provide quite a bit of energy and keep the campsite
> clean too. The tent could be made of a kind of diamondoid foam with
> vacuum within the foam (like a super aerogel) giving the tent a
> reasonable R value (15 or so) so staying warm in the tent would be easy.
> The nano could also collect the evaporated water (and its heat of
> condensation stays in the tent).

Agreed. Given nano, you can get very efficient in every way. In
forget the tent. Just reconfigure your body's resident clothing nanos to
an insulating skin of the type you describe.

>Going nuclear seems a bit excessive for
> this app which has many non nuke solutions.
This is valid, but only to a point. If you had resident body and
nanos, and you had a "mister fusion", then you would be totally
your nanos could recycle your body's wastes, including your exhaled air,
generate food, water and air. Your only requirement would be a place to
dispose of excess heat.

> > If, as you say, nanotech can permit complete recovery of
> > the dangerous isotopes generated
> > by neutron activation, then all that remains is deactivation of those
> > same isotopes. This is also perfectly feasible, because these isotopes
> > can be exposed to still more fast neutrons by recycling them back into
> > the fusion reactor. Most of atoms will eventually transform to stable
> > isotopes under additional exposure to fast neutrons.
> Well, at least the early verions of nano will only be able to
> distinguish elements, not isotopes. Also, any nano working with
> radioactive elements is subject to considerable damage. As for neutrons,
> well, they are oblivious to nanotech, and will happily wander through
> all kinds of matter. I surely wouldn't want a neutron emitting fusion
> reactor in my tent!

Some elements capture neutrons very efficiently, but I want to
start with a reaction that doesn't emit neutrons at all. If we can do
the neutron flux will be very small, due only to incidental fusion when
particles bash into the container walls. I'm not sure, but I
think you can pick structural elements so that the wastes that need to
be separated
are different elements: You don't have to recognize the isotope of
you just have to remember that no nitrogen should be here.

> > The tiny percentage
> > that do not can be separated (again by nanotech)
> So, how do you catch these anyway??

That's not a percentage of neutrons, that's a percentage of waste atoms.
you catch the atoms by recognizing that they are atoms of elements
(heavy metals) that don't belong here.

> and deactivated in a
> > tiny
> > particle accellerator.
> Even nano accelerators will not be very efficient.
It doesn't have to be efficient. It doesn't even have to
break even. It just has to be able to bust up these ugly big
radioactive isotopes that are not amenable to destruction by other
The problem is that for esthetic and political reasons we want this
tiny accelerator to be contained within the "mister fusion" housing.
What I'm banking on here is a major deux ex machina, even worse than
the inertial confinement system above: There are ways to use lasers
to pump energy into a particle beam with extreme efficiency, yielding
a very high change in Mev per meter of acelerator. I further assume that
an accelerator built via nanotech to atomic precision can achieve the
nearly the theoretical efficiency limit. This should permit each nasty
heavy radioneucleotide atom to be bashed with extreme precision into
little pieces that are more tractable, all (I hope) in an accelerator
that's less than a meter long.