[ RadSafe ] Highly Enriched Fuel Reactors

[Jaro Franta]

The point about fission products is interesting.

Recently, someone mentioned that TWR venting of FPs into the sodium coolant
- and also into the "sodium bond" inside the reactor fuel pins - will result
in producing salt species such as sodium iodide (NaI) and Cesium iodide
(CsI): Over time, the TWR will partly turn into a molten salt reactor, even
though it wasn't intended to be one !

Presumably the same holds for the IFR, at least for the "sodium bond" inside
the fuel pins, even if this design doesn't vent FPs to the coolant.

No wonder TerraPower posted a recruitment add for a molten salt expert,
earlier this year....


 Jaro
^^^^^^^^^^^^^^^^^^^^^^^^^





-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of George Stanford
Sent: May-19-13 12:23 AM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] Highly Enriched Fuel Reactors

Guys:

      Regardless of reactor type, you get approximately 1 ton of fission
products for each GWe-yr of energy.  Most of the activity for the first
couple of centuries is due to Cs-137 & Sr-90.  If a 1-GWe TWR runs for 60
years, it will accumulate 60 tons of fission products, and only about half
of the created Cs & Sr will have decayed by then.

      As Jaro says, uranium with enrichment below 20% is considered LEU.

      The TWR publicity that I've seen says that the uranium utilization
will be between 40 and 50 times that of the LWR (which is considerably less
than 1%).  Thus the TWR (as currently planned) would use less than 50% of
the energy that was in the original ore.  Because of the length of time the
residual transuranics have been exposed to the neutron fluence, recycling
the used fuel after 60 years would be difficult because of built-up alpha
activity -- perhaps too difficult to be feasible.

       Consider a 1-GWe TWR.  After 60 years of operation it will have
produced 60 tons of fission products and will still contain more than 60
tons of unused uranium, along with probably a few tons of long-lived
transuranic actinides -- so its initial fuel loading had to contain more
than 120 tons of heavy metal.  It will not solve the waste problem, but it
will kick it 60 years down the road.

      In comparison, the same size IFR  with recycling has a core about
one-tenth the size, and after 60 years will also have produced
60 tons of fission products, disposed of at he rate of one ton per year.
And, with close to 100% utilization of the uranium, the waste will contain
little else.

      -- George

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

At 04:07 PM 5/18/2013, David Lee wrote:
>Joe,
>
>I think, I may be wrong, I was once ;-) It all depends on how deep you 
>burn the fuel.
>Deeper better, more energy output, less fragments to deal with.
>Some one, please, correct me if I am wrong.
>
>
>On Sat, May 18, 2013 at 1:58 PM, <JPreisig at aol.com> wrote:
>
> > Hey All,
> >
> >      So, with these TWR's and other highly enriched  fuel reactors, 
> > with significant use of the fuel, the Cs-137, Sr-90 (i.e. Fission  
> > Fragment) radiation will build up quite quickly.  This will be a 
> > challenge  for Health Physicists, Nuclear Engineers at such 
> > reactors.  Sounds like  fun.  Neutron production will increase 
> > considerably also.
> >
> >     Have a good week.
> >
> >     Joe Preisig
> >
> > PS  I wonder if the bug zapper could be tuned up for tse tse
flies......
> >
> >
> >
> > _______________________________________________
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