[ RadSafe ] Spent reactor fuel

Mon Oct 8 11:54:59 CDT 2012

There certainly is energy in SNF that can be recovered; the question is
"can it be recovered economically?"  While the engineer in me wants the
answer to be "Yes!", I suspect it is not so, for several reasons.  NOTE:
these comments are aimed at the SNF from a BWR, but probably all apply
to PWR fuel, too.  I say nothing about other reactor schemes.

1.  Fuel assemblies are designed to be efficient at transferring heat to
water flowing past them.  This is almost certainly not the optimal shape
for using thermocouples to turn heat into electricity.  
2.  There are hundreds of fuel assemblies in a spent fuel pool, and in
every refueling cycle more are added, and those in the pool already may
get moved around.  This would be made much more difficult if each
assembly had wires leading from thermocouples to some panel.  Also,
while I don't know a lot about making electricity with thermocouples, I
suspect that under water isn't the best place to do it.
3.  Anything that complicates moving spent fuel into the pool will
lengthen the time it takes to refuel the reactor, decreasing revenue,
and increasing dose to workers.  It is unlikely the value of energy
recovered would exceed the increased costs.   

If I were working on a scheme to harvest waste heat from SNF, I would
focus on using the existing spent fuel pool cooling system to move
heated water to a heat exchanger, that then used any of several systems
to do something useful with it.  On the other hand, if I were working on
a scheme to improve the energy output of a nuclear power plant by
harvesting waste heat, I would look first at recovering energy from
coolant heading toward the cooling towers or other heat sink.  The most
efficient use would be to use the heat directly, such as in greenhouses
or heating or public and residential buildings, as is done in Siberia.
Next would be some cycle using some working fluid other than water.  And
fans of the Sterling Cycle usually chime in that this would be a good
place for their favorite system (and they are right).  

As much as I agree that we deal with SNF in a suboptimal way, I suspect
that with current technology harvesting more energy once it is out of
the reactors isn't the worst one.  

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of
JPreisig at aol.com
Sent: Sunday, October 07, 2012 12:36 PM
To: radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] Spent reactor fuel

Dear Franz,

     Well, I'm glad to hear that someone had this idea  many years ago.

Yes, shielding and handling
are clearly issues in doing what I have suggested.  Efficiency may be  a
concern.

     Technology innovations may allow today what could  not be done back
then.  A place like Argonne National Lab or INEL could do a small-scale
Spent Fuel/RTG experiment.  One could probably design some thermocouple
quick-connect mechanism using magnets of whatever to connect a
thermocouple to spent fuel and/or the fuel cladding.  Maybe a robot
could be designed to make such a connection also (No dose to the humans
involved in the experiment)????

    Thanks for your radsafe post, Franz.  Go have a  beer????

    Thanks to Sergio and Roy Herren for their recent radsafe  posts.
Gamma Knife technology is so very interesting.  Read about it on
Wikipedia or on the  internet.

    Regards,     Joe Preisig

In a message dated 10/7/2012 10:32:22 A.M. Eastern Daylight Time,
franz.schoenhofer at chello.at writes:

Joe,
As far as I rememer, this idea is not new - it was already  considerer
when I was a teenager (now I am 68). There must have  been  some
"problems" with shielding,  efficiency and handling - which are
interconnected...... 

You probably remembe the sad story, when  woodcutters discovered in
Siberia a Sr-90 generator and they sat on it,  because it was warm?

Proliferation would be a small  problem!

Best regards,

Franz

--- JPreisig at aol.com  schrieb:
> Dear Radsafe,
>  
>       Howdy all.  I don't know how viable the  following idea is.  It 
> certainly would make anti-proliferation people  nervous.
>  
>      Take some of our (USA or  World???) spent nuclear  fuel, attach 
> thermocouples to the spent  fuel
> and produce localized DC electricity sources (like  RTG's???).
Wonder 
what 
> the total USA energy/power
> generated this way would be???
>  
>     Put solar cells on the roof of such energy/power  sources and
produce 
> even more electricity???
>  
>     Regards,    Joe Preisig
>  
>  
>  _______________________________________________
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--
Franz Schoenhofer, PhD,  MinRat
Habicherg. 31/7
A-1160 Vienna
Austria
mobile: ++43 699 1706  1227

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