RE: Fast moves for nuclear development in Siberia

Sat, 04 Apr 2015 19:46:49 -0700 

 

 

From: [email protected] 
[mailto:[email protected]] On Behalf Of meekerdb
Sent: Saturday, April 04, 2015 6:58 PM
To: [email protected]
Subject: Re: Fast moves for nuclear development in Siberia

 

On 4/4/2015 5:58 PM, John Clark wrote:

On Sat, Apr 4, 2015  'Chris de Morsella' via Everything List 
<[email protected]> wrote:

 

> Has anybody been following this. Looks like the lead cooled fast  breeder 
> design is being carried ahead in Russia.

 

It doesn't need high pressure which is good and, if there is a leak the molten 
lead would soon solidly and self seal which is also good, but the Russians have 
used this sort of design before in their submarines and that's not exactly a 
sterling recommendation in my book. And it makes Plutonium from U238 and that's 
not my favorite element, call me old fashioned but I think the world already 
has more than enough Plutonium in it. I like the Thorium fuel cycle much more 
than the Uranium fuel cycle.


Also thorium is much more abundant.  And it has been demonstrated at Oak Ridge 
as part of the Air Force's program to build a nuclear powered bomber.  I don't 
think any new reactor technology is likely to get built unless some government 
gets involved to fund research and to tailor regulations to the new technology.

 

Also, and this is a major point in its favor LFTR reactor types would be walk 
away safe. Because the U233 fuel plus fertile thorium is solution in the 
fluoride salt coolant a simple and effective failure plug could be designed in 
at the low point of the inner core circulating design. If the reactor ever 
started overheating the plug would be made of a material with a substantially 
lower melting point than the vessel. In other words it would fail first; 
guaranteed.

In this manner the hot fuel/fertile/salt mix (plus various by products in the 
mix) would get channeled into a sub catchment chamber made of neutron absorbing 
materials and with a surface shape that would disperse the hot liquid core 
circulating fluid over a relatively wide flat area beneath the reactor, and 
without any intervention the reaction speed would very significantly slow down 
(free neutron starvation); the hot liquid (also radioactively very hot of 
course) fluid would cool down and solidify into what can be pictured as a kind 
of cupcake shaped containment.

It would still be a big cleanup, but it would be a manageable one that would in 
many senses have elf-contained itself.

Another advantage of the LFTR design is that they have a broader neutron 
bandwidth (being able to utilize both fast neutrons as well as slower 
neutrons). I guess one could say LFTR has a higher neutron efficiency; being 
able to use them across a broader spectrum of energies.

Whatever the breeder fuel cycle: LFTR or the (seems like the Russians are going 
in that direction) plutonium economy; inherent passive safety features are 
critical. If we learned anything from Fukushima, I would argue that one of the 
lessons must be that reactors need to be walk away safe, being designed with 
in-built passive safety designed failure modes. This also argues for smaller 
scale units than behemoths like the MarkII design. The very big units just 
generate too much heat all, in a remarkably small place… too much for passive 
safety to be practical. I think a better reactor scale would be around 200MW, 
big enough to matter, but small enough to be manageable in failure mode.

Chris

Brent

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