[AR] Re: HEU salts in water was methane to methanol
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 2 Jun 2017 18:16:56 -0400 (EDT)
On Fri, 2 Jun 2017, Keith Henson wrote:
...There is no question that the fuel is very expensive
Right, even with centrifuges, the 235 to 238 mass difference make it
hard to sort out. There might be a alternative, a cheap way to make
plutonium 239 that is virtually free of Pu 240 and higher. The idea is
to sort out the Pu before it has a chance to pick up another neutron.
NSWR is a continuous moderated slow-neutron system -- the water provides
the moderation -- and so it actually doesn't care about the presence of
higher isotopes. (Precisely-timed fast-neutron chain reactions do,
because they can't tolerate much stray-neutron background, and Pu-240 in
particular has a very high spontaneous-fission rate.)
Alas, "cheap" is relative here. :-) Plutonium made by this route, or any
other, is likely to be more expensive, not less, than enriched uranium (if
we quietly disregard the capital costs of building the enrichment plant,
which is probably more expensive than a reactor). Anything made by
neutron transmutation is inherently hideously costly, because there are a
lot of neutron losses, and you must fission multiple kilograms of U-235 to
get enough neutrons to transmute a kilogram of uranium into plutonium.
And the U-235 usually must be supplied in at-least-slightly-enriched
uranium, too.
and the exhaust would be very radioactive. There are potentially serious
design difficulties, notably preheating of the fuel in the plumbing en
route to the chamber.
I have never looked into this kind of rocket. Why does the fuel need
preheating?
It doesn't need it or want it, but will get it regardless. The neutron
and gamma fluxes coming out of the chamber will be very high indeed.
Henry
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