The rest of the article is interesting too, but some of the background
material is particularly interesting, IMHO.
The interview with James R. Powell of Plus Ultra Technologies (PUT, at
http://www.newworlds.com/index.html ) starts about half-way down the page at
http://www.nuclearspace.com/A_HEADNA.HTM
<begin quote>
I started in Brookhaven National Laboratory (BNL) out of graduate
school in Nuclear engineering, I was MIT's (Massachusetts Institute of
Technology) first doctoral student in nuclear engineering under Manson
Benedict. I joined the Nuclear Engineering Department in Brookhaven in '56.
In those early days in Brookhaven, and a lot of national labs around the
country, you had a great deal of freedom in what you could work on.You don't
see that kind of freedom these days. People are very constrained. In order
to be funded you have to part of a work break down structure with an
infinite number of milestones that are micromanaged to death.
Our funding for the whole department was done by the chairman. In
April he would write a one page letter to the AEC saying how much money he
wanted next year. So, as a result you could do many different and
interesting things, a lot of which wasn't micromanaged.
One of the things I was working on was non-equilibrium plasma
conversion, MHD generators for reactors to make them more efficient. I also
was working on a space power system using a "Liquid Cesium" piston instead
of a mechanical turbine. I did a lot of work on Rayleigh Taylor
instabilities, built MHD generator models and tested them and so on. That
got me interested in space propulsion. I stopped working on space systems
after the NERVA program ended. Then, I did a lot of work on Fusion Reactors.
I then came back in the '80's to the question. How do you get a really small
high power density reactor ?
The answer, is you make the fuel elements out of packed beds of very
small HTGR (High Density) fuel particles so you get a large heat transfer
area per unit volume. We proposed this at the Air Force Rocket Lab and we
did some nice work there. SDI they started a major program on the PBR
nuclear rocket. The $200 million dollar program involved: Grumman, Babcock &
Wilcox, Sandia, Hercules, Garrett and a couple other companies. We made a
lot of progress during the five, six years on the program. We developed very
high temperature fuels and materials, built reactors and tested hardware. We
were on the path to ground test an engine that would have been much smaller
than NERVA. When the Cold War ended, however the program was shutdown.
So, there was a hiatus of several years. Toward the later part of
the '90's we then proposed the small MITEE reactor for robotic exploration
of space.
So NASA has come back to nuclear propulsion and it seems like
they're serious.
But as you say, will it follow through or will it be another on
again, off again program - I don't know.
<end quote>
Also note that PUT's MITEE (MInature ReacTor EnginE) rocket reactor concept
resembles a CANDU, in the sense that it involves the use of pressure
tubes... except theirs are beryllium, combining neutron moderation with
pressure boundary ("Each pressure tube contains an outer annular cylinder of
7LiH moderator, and an inner annular rod of perforated tungsten 235UO2 metal
matrix composite fuel sheets. Cold hydrogen propellant flows downwards at
~100 K along the outer surface of the 7LiH moderator, then radially inwards
through the moderator and the tungsten - UO2 fuel sheets. The hydrogen
propellant emerges from the final fuel sheet at 3000 K, and then flows
longitudinally down through a central hot gas channel to the exit nozzle at
the end of the pressure tube.").
Jaro
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