[ RadSafe ] What is a Travelling Wave Reactor?

[Brennan, Mike (DOH)]

Hi, Dan.  

I have no firsthand knowledge of the process, but have done some reading
and thinking about it.  

First, consider the "conventional" breeder reactor.  Start with a
nuclear reactor (liquid metal fast reactors are best), and surround it
with a "blanket" of rods with U238.  The core is designed and run in a
way to produce lots of neutrons and leak them out of the core, into the
blanket, where they are absorbed, converting U238 into some flavor of
plutonium, after a couple of decays.  At some point the blanket rods are
pulled, processed to remove the Pu, which is then used to make more fuel
that can be used in the breeder or some other reactor.  So, fission
takes place throughout the core, breeding takes place throughout the
blanket.

In a TWR, the fuel is designed so that fission takes place at a critical
level at one "end" (the geometry is likely more complex, but it can be
visualize that way).  Some of the neutrons leaking out of the volume of
fuel where the fission is taking place hit U238 atoms in the volume of
fuel next to it (where there are not enough fissile atoms to support
criticality).  Over time the fissile atoms in the volume of criticality
burn up, until criticality can no longer be maintained.  At the same
time, more and more fissile atoms are being created in the volume next
to the criticality.  If the system is designed correctly, at about the
same time as a given volume at one end of region of fission has run out
of fissile material and cannot remain critical, a volume at the other
end will have bred enough fissile atoms so it can start sustaining
criticality.  Fission and breeding both take place in a limited portion
of the system, and that place moves over time.

To use a combustion analogy, a TWR is like a fuse; you provide enough
energy to get the reaction started in one place, then the energy from
that reaction starts the reaction in the part of the fuse next to it.  A
TWR is a nuclear fuse, designed to burn for 100 years.  

I can see a couple of non-trivial technical issues, but conceptually it
is fairly straight forward.  If Terapower has convinced Bill Gates and
his advisors that they can overcome the technical issues, I don't think
I would bet against them.  


-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Dan W McCarn
Sent: Thursday, March 25, 2010 11:11 PM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] What is a Tavelling Wave Reactor?

Dear Group:

 

Bill Gates is going nuclear.  What is a Travelling Wave Reactor (TWR)?

 

http://tinyurl.com/TWR-BG

 

I've read the Wiki article but am still in the dark about how this
reactor
operates.

 

http://en.wikipedia.org/wiki/Traveling_wave_reactor

 

Dan ii

 

--
Dan W McCarn, Geologist
2867 A Fuego Sagrado
Santa Fe, NM 87505
+1-505-310-3922 (Mobile - New Mexico)
 <mailto:HotGreenChile at gmail.com>  <mailto:HotGreenChile at gmail.com>
HotGreenChile at gmail.com (Private email)

 

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