Most messages had to do with Pu and atom bombs, not with the NEW OPTION.
I am not surprised; it is rarely known, even among research physicists.
I do not know why. In any case let me summarize what I learned last year.
Imagine a subcritical reactor. This is a device in which a self-sustained
chain reaction is impossible unless an external source of neutrons is
introduced. The multiplication factor k may be 0.95 or so. No control rods
are necessary; remove extrnal neutrons and the chain reaction will be
"switched off" immediately. This is a big safety factor against the
so-called "criticality" accident!
How are external neutrons produced? There is a thick molten-Pb target in
the center of the reactor (a vessel of about 1 meter long and 0.2 m. wide).
Protons from a very powerful accelerator (e.g., 1000 MeV and at least 10 mA)
are absorbed in the target, producing a lot of neutrons. The technical name
for this system is "spallation neutron source". Each proton will produce,
on the average, about 25 neutrons. And each neutron will be multiplied
by a factor of 20 in the subcritical reactor (assuming k=0.95. The factor
is larger when k is closer to 1; for example 100 when k=0.99).
That is it. But there are many ways to implement the idea. The Los Alamos
proposed system has a reactor in which the fuel is dissolved in molten salt
circulating (driven by pumps) through graphite blocks. A chemical processing
plant, at the site, will be used to remove "poisons" as often as necessary
or to add more fuel. Another function of the molten salt is to transfer
energy to a heat exchanger. The concentration of heat-producing fission
products is always very low and this is a safeguard against melt-down. Thus
neither criticality nor meltdown accidents (as in Chernobyl and Three Island,
respectively) are possible.
The European design (Rubbia in CERN) uses fast neutrons and solid fuel
(traditional pellets). No on-line chemical processing is necessary but the
reactor must be stopped for refueling every four or five years. The fuel
assemblies are suspended in liquid lead whose function is to serve as a
spallation target and as a heat tranferring medium. No pumps are used;
heat transfer is passive; it is based on convection. Unlike pumps,
convection never fails and this is the safeguard against the meltdown.
In Japan both molten salt and solid fuel approaches are followed. My
prediction is that Japan will be the first to build the device because
their scientists have full support from government and industry. It is
hard to get financial support in the present "immediate benefits" attitude
in both U.S. and Europe. The processing of civilian reactor waste is
actually illegal in U.S. and the laws must be changed to open the path for
new technology. Will this happen? Or will we be importing "made in Japan"
hybrid systems 20 to 30 years from now? What else is new with good original
"made in USA" ideas? Presently functionning reactors are aging.
Nuclear electricity is desirable (as long as other alternatives, such as
solar, are not available) to stop sending CO2 into air. CO2 from fossil
fuels is contributing to the now-undeniable global warming trend.