[AR] Manhattan Project (was Re: Skylon and related...)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 14 Feb 2018 19:34:07 -0500 (EST)
On Wed, 14 Feb 2018, John Dom wrote:
...Mass-spectrometer enrichment looked much more simple and certain...
it produced the first uranium bomb cores. And in fact most of the
early bomb cores came from water-cooled graphite reactors producing
plutonium...
Oak Ridge works.
And Hanford works, for plutonium. Originally the plan was to put
everything at Oak Ridge, but Groves eventually decided that large nuclear
reactors should be located in an area of lower population density, in case
something went badly wrong.
Odd the first fission bomb (Alamogordo desert) was a "tricky" cast
plutonium implosion device. Not the simple uranium gun option: that was
unleashed above Hiroshima.
The uranium gun wasn't felt to need a full-scale test. Its (relatively
poor) performance could be predicted fairly well from experiments like
dropping a U-235 slug through a U-235 ring repeatedly, and watching the
neutron pulse get bigger as more U-235 was added to the ring.
Whereas subscale implosion tests were so difficult, and the results were
so hard to interpret, and implosion development had been so rushed, that
sacrificing the first plutonium core in a test was considered necessary to
qualify the design for combat use. There was real uncertainty about
whether it would actually work.
I have references of several of nuke test lists but does anyone have a
test-named list detailing uranium or plutonium was used?
I believe this isn't openly known for most of them. (There was also
substantial use of "composite cores" containing both U-235 and plutonium.)
Browsing I further read to my surprise uranium can be cast just like
plutonium into a sperical geometry for implosion devices.
Yes, there's no problem with that. It turned out to be impractical to
build a plutonium gun bomb -- hence the last-minute scramble to produce a
workable implosion design -- but implosion works with either fuel, or
combinations. The biggest fission bomb ever exploded (about half a
megaton) was a uranium implosion design.
Gun bombs are so inefficient, and thus need such dangerously large amounts
of fission fuel, that once implosion was a proven technology, gun bombs
were abandoned except for a few specialized uses where implosion was
impractical for one reason or another. (The uranium needed to make one
gun bomb could make several implosion bombs with the same yield.)
Henry
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