On Fri, 24 Feb 2012 18:11:39 -0600, Richard wrote:

On 2/24/2012 6:04 PM, Jon Elson wrote:
Ed Huntress wrote:



Well, that *is* really a problem. All of the plutonium in the world
won't get them a bomb, but the gun trigger for Little Man could
probably have been made in a good basement shop. That's why it's a lot
scarier for them to have enriched uranium than plutonium. Any goof can
make a gun-trigger uranium bomb, if they have a plan that gives them
useable dimensions.
Anybody that has more than a gram of 239 Pu ALREADY has enriched
uranium. You need "weapons grade" enrichment, meaning about 90% 235U)
to build a breeder reactor to make 239 Pu. It has to be a fast neutron
reactor to transmute the 238 U at the edge of the core to 239 Pu, and
that requires a high proportion of 235 U for the chain reaction to
continue. (I'm not a reactor physicist, but that's my understanding.)
So, if they have kilograms of 239 Pu, they MUST have tons of pretty
pure 235 U.

Jon


I wonder where they got the 235U?

Any peaceable nuclear reactor needs U-235 to fire the reaction -- it's
just that the common type (non-breeder) doesn't need much.

I'm not so sure about the absolutely needing a breeder reactor -- AFAIK,
you get Pu from ordinary reactors, just in small quantities. In fact,
(again, AFAIK), part of the reprocessing of nuclear fuel is getting the
Pu out.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com