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Re: a nuclear topic

On Sun, 28 Dec 1997 15:32:16 JACK L. URETSKY (C) /1996; HEP DIV., ARGONNE
NATIONAL LAB, ARGONNE,IL 60439" <JLU@HEP.ANL.GOV>/ wrote:

According to the Los Alamos guy who spoke at Argonne ... the "accelerator"
idea for converting nuclear waste is essentially an IFR under a politically
correct name. ...

I would disagree with this guy. The IFR (Integral Fast Reactor) and ADTT
(Accelerator Driven Transmutation Technology) are functionally similar but
these are very different animals. Both address the nonprolifiration issue
and both are designed to "burn" actinides and transmute fission products.
Turning long-term radioactive products into stable, or rapidly decaying,
nuclei is the common characteristic of these two machines. It offers an
alternative to geological repositories, such as Yucca Mountain (see Physics
Today, June, 1997). But the ways of doing this are quit different.

To learn about IFR see Progress in Nuclear Energy, vol 31 # 1/2, 1997. To
learn about ADTT see the unpublished article on my web page (html://www.
csam.montclair.edu/~kowalski) and its refernces. There are several talks
on "Nuclear Energy Today and Tomorrow", at the AAPT meeting in New Orleans
next week, including my own. Come to the session FC, on January 7, if you
are interested.
Ludwik Kowalski
P.S.
IFR is a reactor concept developed (many components were actually tested) by
more than 100 nuclear experts between 1984 and 1994. Then "Congress acceded
to Administration wishes and ordered that develompent ... be terminated". It
was an advanced fast neutron breeder cooled by liquid sodium and powered by
metallic fuels (not by common oxide fuel). The waste was to be handled
internally using new "pyroprocessing technology". Actinides: Np, Pu, Am,
Cm, etc. would never be separated from each other. (A mixture would be not
suitable for diversion but would burn as an energy producing fuel.)

As I read about the ADTT, with which I am more familiar, I do see that many
concepts are borrowed from IFR (or vice versa?). But ADTT is VERY different
in many ways. Most importantly, IFR is a critical reactor while the fuel
blanket of the ADTT is subcritical. Furthermore, the ADTT devices proposed
by LANL operate on thermal (moderated) neutrons while IFR has no moderator.
IFR uses solid fuel while ADTT uses the fuel disolved in the liquid salt
which circulates through the high flux area. The salt is processed on-line
to optimize the performance. The "neutron economy" of ADTT is fantastic;
the chain reaction would be possible with that machine, in principle, even
if no neutrons were emitted in the fission process itself!

The blanket of the thermal ADTT has only about 100 kg of fuel while the core
of a fast breeder has about 10,000 kg of it (because thermal neutron cross
sections are much larger than cross sections for fast neutrons). In my
opinion the ADTT approaches are better than IFR. But I am not a nuclear
engineer.