RE: MOX Program

["Franta, Jaroslav" <frantaj@aecl.ca>]

Ron, Group,

Its not that simple, unfortunately.

While its true that "Pu-240 is not fissile," this only means it can not
support a thermal neutron chain reaction. But Pu-240 CAN support a FAST
neutron chain reaction (neutron energy ~ 0.5 to 4 MeV). This is quite unlike
U-238, which can't do either (but is called fissionable, because it can be
fissioned by VERY fast neutrons - like those from hydrogen fusion reactions,
i.e. energy > 4MeV). For that reason, a new term has been coined for
nuclides like Pu-240 (which also includes Pa-231, Am-241 and Np-237), dubbed
"fissible."

I think that Jacques Read said it best when he wrote that "It is
theoretically possible to drive any fissile material to super-criticality if
you use enough chemical high explosive to compress it, but the fission
density suffers and the resulting object doesn't give a big multiplier over
the same weight of TNT." ...its just that he was being a bit liberal with
his usage of the word "fissile" (am I right, Jacques ?).

Its very educational to view the differences in fission x-sections as a
function of neutron energy. You can do this by going to an interactive
nuclear x-sections database like the one at JAERI, and plotting out the
x-section curves for these nuclides.
The web site is at
http://wwwndc.tokai.jaeri.go.jp/Figs/endfplot.html

For your convenience, I have prepared one such graph, with the following URL
- which I'm hoping you can manage to stuff into your web browser address
line - let me know if it works... it worked when I clicked on the URL in
this message, but it will get chopped up in the Radsafe posting & will need
to be reassembled on your web browser address line; also, give it a couple
of seconds before the graph appears -- the first display is the input page,
which then automatically switches to the plot... in the worst case, I can
always just send you the picture to your personal address) :
http://wwwndc.tokai.jaeri.go.jp/cgi-bin/w3endf/?lab=Pu239%3BPu240%3BU238&mt=
Pu-239%3D18%2FPu-240%3D18%2FU-238%3D18&ax=log&e0=50000&e1=4000000&ay=log&y0=
0.0001&y1=10&sx=&sy=

PS. my offer of an AVI color animation illustrating the real problem in
making RGPu bombs, called "Mark's RGPu dud," still stands (it was initially
made in a Radsafe post of Wednesday August 16, 2000 2:43 PM), in case you
are interested.   BUT PLEASE DON'T reply on RADSAFE - contact me personally
at frantaj@aecl.ca 

Regards

Jaro 

-----Original Message-----
From: Ron L. Kathren [mailto:rkathren@tricity.wsu.edu]
Sent: Wednesday August 23, 2000 5:00 PM
To: Multiple recipients of list
Subject: Re: MOX Program


Pu-240 is not fissile; it cannot therefore support a chain reaction and
cannot be made into a nuclear explosive.  It is physically impossible to
make a bomb with Pu-240, unless there are some new laws of physics.

Ron Kathren


----- Original Message -----
From: William Prestwich <prestwic@mcmail.cis.McMaster.CA>
To: Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
Sent: Wednesday, August 23, 2000 6:50 AM
Subject: MOX Program


> The MOX program is being criticized as not fulfilling its purpose
> of rendering the fuel unusable for nuclear weapons. The Carson Mark report
> is quoted as stating that any mix of Pu isotopes may be used to make a
> weapon. I know there were excellent postings on this subject-I am sorry to
> say I haven't yet found out about going to the archives. But the above
> statement would imply in the extreme that a weapon could be made using
> pure 240Pu-is that really possible?
> If anyone has the time, could they please enlighten me directly,
> unless they feel their comments are beneficial to the community at large.
> Thanks,
> Bill Prestwich
> McMaster University,
> Hamilton, Ont.
> E-mail: prestwic@mcmaster.ca
>
> ************************************************************************
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information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html