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PostPosted: Nov 22, 2013 9:41 pm 
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The Nobel prize Carlo Rubbia gave a speech in the ThoriumEnergyConference 2013 at Geneva.
You can see all the presentations here : http://thoriumenergyconference.org/Program
Here the PDF presentation of Rubbia : http://thoriumenergyconference.org//sites/default/files/pdf/A%20Future%20for%20Thorium%20Power%20-%20Carlo%20Rubbia%20-%20IASS%20-%20ThEC13.pdf

He also intervenes in the speech of Hongjie Xu (at 34 minutes).

If I understood well I can summarize his main points of view :

Rubbia is not really attracted by Molten Salt Reactors because :

  • It is more difficult to insure the absolute stability of the multiplication factor k because the fuel doesn't have a determinate shape and you can have phenomena like oscillations, waves, etc.
  • It's more difficult to contain radioactivity in case of accidents because the fuel is mobile and always moving, you can have leaks.
  • Online reprocessing is complex, costly and risky.

Rubbia supports Thorium reactors but :
  • Thermal breeders require too much reprocessing so It's better to use fast or epithermal breeders.
  • Solid fuel reactors are simpler and more conservative.

Rubbia supports an accelerated driven lead cooled fast reactor (or molten salt cooled with LiF-BeF2), the Energy Amplifier. In order to keep this solution practical and cheap, the Energy Amplifier has the following specifications :

  • Long fuel cycle ( solid fuel rods stay in the core from 10 to 15 years )
  • Very long reactor lifetime ( > 200 years )
  • Very simple dry reprocessing of the fuel
  • Small cheap accelerator (first the core is supercritical, then we make it subcritical by using control bars to have k=0.997 and then the accelerator beam gives us enough neutrons to have a steady power)

I guess lot of people here will disagree with him. I was curious to know what do you think about his conclusions and his suggestions.


Last edited by fab on Nov 23, 2013 7:09 am, edited 1 time in total.

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PostPosted: Nov 22, 2013 10:07 pm 
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What I couldn't fathom, as I listened to his talk there in Geneva, was how on one hand he could reject the molten-salt reactor as being "too complicated", yet proceed to advocate for the use of each and every one of the molten-salt processing steps (fluorination, reductive extraction, etc.) for his solid-fueled reactor! And then, adding to the titanic complexity of his reactor his new-found desire for molten-salt cooling (of metal-clad solid fuel) and the ever-present, ever-unnecessary accelerator.

There was a lot of incredulity amongst the reactor people in the group about his talk.


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PostPosted: Nov 22, 2013 11:08 pm 
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Kirk Sorensen wrote:
What I couldn't fathom, as I listened to his talk there in Geneva, was how on one hand he could reject the molten-salt reactor as being "too complicated", yet proceed to advocate for the use of each and every one of the molten-salt processing steps (fluorination, reductive extraction, etc.) for his solid-fueled reactor! And then, adding to the titanic complexity of his reactor his new-found desire for molten-salt cooling (of metal-clad solid fuel) and the ever-present, ever-unnecessary accelerator.
He's obviously due for another Nobel Prize !


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PostPosted: Nov 23, 2013 1:13 am 
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Rejection of molten salt to carry fuel may be unjustified but its adoption as coolant in fast/high temperature reactors is not. Even in a sodium cooled reactor, it could be used with advantage as as the secondary coolant. An accelerator is, of course, an unnecessary complication.
Spent fuel may be a small part by volume of radioactive waste, but it must be recycled to control build up of radio-toxic wastes. Availability of fresh uranium may experience a fall due to increased resistance to mining in many parts of the world. The breeders or a reduction of net consumption of mined fissile are a must. There are large stocks of easily mined thorium and reprocessed and depleted uranium fertiles and they have to be used as nuclear fuel. PHWR and fast reactors are best ways to do it. Graphite moderator has low life and is therefore messy.
PHWR with Radkowski fuel system could be a breeder or near breeder. U-233 produced in thorium blanket is the best fissile available and could be used in any of the reactors. U-238 is the best fertile in a core due to fast fission bonus.


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PostPosted: Nov 23, 2013 8:28 am 
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Thanks all.

Quote:
yet proceed to advocate for the use of each and every one of the molten-salt processing steps (fluorination, reductive extraction, etc.) for his solid-fueled reactor!


Thanks Kirk, I guess Rubbia wanted to decrease the number of reprocessing facilities to diminish public concerns, diminish capital costs, and have economy of scale. Maybe he thought that using solid fuel will also be more accepted because it's more conservative and we already have a lot of experience with them.

Quote:
Rejection of molten salt to carry fuel may be unjustified but its adoption as coolant in fast/high temperature reactors is not


Yes, using Flibe instead of sodium sounds a great idea and will greatly diminish public concerns about solid fuel fast reactors. And they already have Hastelloy N to deal with the corosion of the salt contrary to the case of using lead . In fact LiF-BeF2 will softer the spectrum and it will maybe difficult for an U/Pu reactor to breakeven but it's still good for a Th/U breeder. For a U/Pu reactor maybe they can use clean chloride salts.


What seems really strange it's the fact that his core is supercritical, then he uses control bars to make it subcritical and then uses a small accelerator in order to have a steady power. Why not use only control bars ? He said that a small accelerator is as costly as a control bar and it's a lot easier to control the core with an accelerator than with a control bar. But in this case his core is near criticality (k=0.997).

I thought the fact to have a subcritical core in a fast reactor allows you to deal with great insertions of reactivity ( core compaction, reflector and moderator insertion, mishandling or withdrawing of control rods, ...) but you need great margins to criticality (for example k=0.97 see : http://citeseerx.ist.psu.edu/viewdoc/download?rep=rep1&type=pdf&doi=10.1.1.216.3106 ).

Then you don't use any control rods and you can really claim deterministic safety about criticality control. It's not the case with the Energy Amplifier, but I maybe miss something ?


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PostPosted: Nov 23, 2013 1:22 pm 
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It was disappointing to hear such a highly respected person say so many wrong ideas/opinions/facts. To mention a few:

- The Fukushima nuclear accidents proved the safety of current nuclear power, not the danger (i.e. 0 fatalities).

- He claimed that most of the world's uranium was in the ocean. In fact, as with thorium, most is in the rocks, but unlike thorium, additional U is in the seas. If we chose to exploit the ocean U, over a geological time scale, it would be replenished from the rocks by erosion etc.

- His understanding of thorium use in LWRs and HWRs was limited to the once-thru cycle using Radkowsky fuel design. In fact, it has been known for decades that both can be operated as break-even thorium cycle breeders when reprocessing is used; LWRs and HWRs on the thorium-reprocessing cycle need frequent fuel reprocessing to break-even, which hurts economics, but economics and refueling-interval improve greatly when they are used as near-breeders with Pu or HEU fuel top-up (but proliferation resistance degrades).

- He shoots down the MSR (the 1960s molten salt reactor concept) based on the undesirability of rapid reprocessing, but neglects to mention the 1980s DMSR, which would go 30 years between reprocessing, and uses an extremely proliferation-resistant fuel cycle.

- He takes comfort in the safety implications of fast electronic shutdown (using the accelerator, which as noted by Fab can be over-powered by the control rods!), but ignores the much more compelling safety argument for automatic passive reactivity control (e.g. thermal feedback in all reactors, moderator boiling in LWRs, fluid-fuel expansion in MSRs, fuel expansion/extrusion in pancake-core IFR).

We already know how to make inexhaustible energy from uranium (using the IFR fast reactor) or thorium (light water or heavy water breeders); we simply choose not to use these methods because they currently cost more than the uranium once-thru cycle in LWRs. It doesn't make any sense to recommend other reactor types that cost more than LWRs.

There is reason to believe that LFTR and DMSR could meet or beat the cost of LWRs, but this does not appear to be true of any fast reactor (due to the cost of the initial fissile load).

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PostPosted: Nov 23, 2013 9:00 pm 
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Nobel prize doesn't mean anything.

All a nobel prize means is that the Royal Swedish Academy of Sciences likes you.

LFTR will be a reality, if the west rejects reality, then the nuclear dragon china will make mobile LFTR and sell mobile LFTR to the west.


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PostPosted: Nov 23, 2013 9:18 pm 
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NicholasJanssen wrote:
Nobel prize doesn't mean anything.

All a nobel prize means is that the Royal Swedish Academy of Sciences likes you.


Or you found a new subatomic particle...

Seriously, though, ever since Geneva I have had a very simple question for Rubbia and the other ADS guys...if you plan to build a fast-spectrum reactor, like they propose, then why mess around with thorium?

The entire reason to consider thorium is for breeding in thermal-spectrum reactors, and to avoid the inventory, coolant, and controllability issues of fast-spectrum reactors. If you plan to bite off the challenge of fast spectrum anyway, then JUST USE URANIUM!

I really don't get why they want to use thorium in a fast-spectrum reactor. It isn't as if we lack for supplies of depleted uranium.


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PostPosted: Nov 23, 2013 9:24 pm 
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I think they want to have it both ways.

Thorium still manages to put several fissile or semi fissile isotopes between the feedstock and the truly nasty Americium and Curium isotopes.

Very little of the fuel will make it out of uranium in all likelyhood and thanks to 237Np almost none will make it to Plutonium.


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PostPosted: Nov 23, 2013 9:33 pm 
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The fuel cycle performance of a LFTR, ADS, LMFBR, IFR, LWR or any reactor is entirely dependent on some rather arcane details of the fuel processing system. We don't have nearly enough details on LFTR yet, but I present basically everything I know about LFTR processing at each conference I go to, including ThEC2013.

The ADS guys say NOTHING about processing, processing efficiency, actinide loss in fuel dissolution, actinide loss in fuel re-constitution, etc.

One can make NO claim about the performance of a "reactor system" if one omits the gory details about this all-important aspect of their performance. I'm embarrassed how little we know about this from a LFTR perspective, but compared to us, the ADS guys are light-years behind.


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PostPosted: Nov 23, 2013 9:45 pm 
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Quote:
then why mess around with thorium?


Like E Ireland, I think they want to diminish the inventory of minor actinides while conserving a fast spectrum.


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PostPosted: Nov 24, 2013 12:03 am 
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Kirk Sorensen wrote:
NicholasJanssen wrote:
Nobel prize doesn't mean anything.

All a nobel prize means is that the Royal Swedish Academy of Sciences likes you.

Or you found a new subatomic particle...
Seriously, though, ever since Geneva I have had a very simple question for Rubbia and the other ADS guys...if you plan to build a fast-spectrum reactor, like they propose, then why mess around with thorium?
The entire reason to consider thorium is for breeding in thermal-spectrum reactors, and to avoid the inventory, coolant, and controllability issues of fast-spectrum reactors. If you plan to bite off the challenge of fast spectrum anyway, then JUST USE URANIUM!
I really don't get why they want to use thorium in a fast-spectrum reactor. It isn't as if we lack for supplies of depleted uranium.

Thorium produces U-233, the superior fissile isotope. Irradiate thorium in the blanket and spice up the core after extracting the U-233. It will reduce the production of higher actinides but that is a minor detail, as they can be burnt in a fast reactor.
Benefits of the MSR and the fast reactors can be added together in a fast MSR.
P.S. If you are an Indian or not on good terms with the Nuclear Five, go for thorium breeders as early as possible.


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PostPosted: Nov 24, 2013 10:06 am 
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This presentation talks about advantages and disadvantages of using Thorium in a solid fuel, sodium cooled, fast reactor :

http://thoriumenergyconference.org/sites/default/files/pdf/Fast%20Reactor%20Physics%20-%20K%20Mikityuk%20-%20PSI%20-%20ThEC13.pdf


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PostPosted: Nov 24, 2013 10:35 am 
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fab wrote:
Quote:
then why mess around with thorium?


Like E Ireland, I think they want to diminish the inventory of minor actinides while conserving a fast spectrum.


From a long-term radiotoxicity perspective it doesn't make much difference if you eliminate the minor actinides while letting lots of uranium isotopes escape into your waste stream, as would happen if a solid-fueled thorium ADS reactor operated with the batch reprocessing approach that Rubbia favors.


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PostPosted: Nov 24, 2013 12:58 pm 
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I think Rubbia also prefers thorium to uranium, because right or wrong he believes it's much less prone to proliferation


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