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PostPosted: Mar 02, 2013 12:22 am 
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So, basically this is a Na IFR, but much bigger because they load all the fuel in at beginning of life (and pay for it then, i.e. one of the problems with current PWRs is initial cost). This is especially costly for a fast reactor.

This would seem to require a massive Na inventory as well. Coolant is flammable and reacts with water.

Many coolant flow paths are a nightmare and require extra pumping power.

They have refueling shutdowns just like PWR's or normal IFR's, they just don't open the Reactor.

They have massive burnup and neutron fluence problems to overcome, with several work arounds like metalic fuel, sodium filled cladding, vented fuel (not too happy about that one). This is the reason I prefer LFTR's, even higher burnup, but no fuel damage concerns.

They keep the spent fuel inventory around the core and keep it activated, so any accident scenario would include it.

The design is still going through significant changes from candle TWR, to pebble in a pond TWR, to standing wave by shuffling fuel. Technically, CANDU is a standing wave reactor with water instead of sodium.


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PostPosted: Mar 02, 2013 12:48 am 
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Cyril R wrote:
Tin and lead fluorides are very corrosive. In fact you'd be better of with pure lead coolant than lead fluoride.

Lead is a pretty good coolant for a fast reactor. Lead is corrosive to nickel alloys but not to zirconium, niobium, molybdenum with proper oxygen control. Would be nice for a CANDU as well, especially if using radiogenic lead, from thorium deposits, when thorium decays it eventually becomes Pb-208, the best lead isotope for reactor coolant. Lead doesn't moderate, so in a lead cooled heavy water moderated CANDU it means you have a bimodal spectrum and can breed much better with both U-Pu and Th-U. Lead is compatible with the zirconium alloys used in CANDUs so you can just make the entire primary loop out of that, and maybe a TZM steam generator tubing.


Some of the Russian nuclear submarines used Pb as a coolant.


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PostPosted: Mar 02, 2013 1:07 am 
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And where are those reactors now............................?

Defunct? Most Decommissioned in 1990. According to wikipedia they were expected to have a short life, probably due to PbBi corrosion of the vessel.

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


Last edited by Ed P on Mar 02, 2013 2:20 am, edited 1 time in total.

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PostPosted: Mar 02, 2013 2:06 am 
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Ed P wrote:
And where are those reactors now............................?

Defunct?


At least one sunk with its submarine. I think that the others are defunct.

I got the information from the book Plentiful Energy by Till & Chang. They strongly support the IFR and strongly defend the Na cooling. However, the reprocessing of the fuel to me seems somewhat awkward. They have to chop up the fuel rods, including the stainless steel cladding, before using what amounts to a modified electroplating process. Making the fuel rods includes a casting process. And, unlike the LFTR, it has to be shut down for refueling. The IFR may well be practical, but the LFTR approach seems much simpler to me. However, I think that it would be a mistake to rule out the IFR approach completely until it can be established that the LFTR can be scaled up and have a long trouble-free life; it could have serious problems which are not yet apparent. I seem to recall something about putting all of one's eggs into one basket. We've already made that mistake with the PWR.

Actually, I don't have the right degree to understand this sort of thing so probably I'm not qualified to have an opinion.


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PostPosted: Mar 02, 2013 4:49 am 
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I am sure an enamel to protect a reactor material from any coolant can be found. It could be silica or pyrolytic carbon or SiC. Fire prone sodium needs replacement as heat transport agent.


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PostPosted: Mar 02, 2013 8:35 am 
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jagdish wrote:
I am sure an enamel to protect a reactor material from any coolant can be found. It could be silica or pyrolytic carbon or SiC. Fire prone sodium needs replacement as heat transport agent.


@jjagdish, Everything is relevant. Would you rather have a coolant that burns (Na) on contact with air or one that vaporizes on contact with air, causing immediate loss of cooling, producing hydrogen gas, that explodes.............................. :lol:


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PostPosted: Mar 02, 2013 3:50 pm 
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jagdish wrote:
I am sure an enamel to protect a reactor material from any coolant can be found. It could be silica or pyrolytic carbon or SiC. Fire prone sodium needs replacement as heat transport agent.


Depending on a coating that could be breached is also risky. Even a scratch that would enable the coolant to contact the base metal could create serious problems. In earlier times, cars had chrome trim, which was actually plated steel. Bumpers (fenders in British English) were chrome. In areas where salt was used for melting ice, even the slightest scratch to chrome plated parts resulted in rust.

Na for cooling does have it's problems, but the authors of Plentiful Energy, i.e., Till & Chang, believe that dealing with the reactivity of Na is a problem that can easily be dealt with. They provide examples. Even so, I'd think that it would be inconvenient. Surely it would complicate refueling since the entire operation would have to be done within an Ar blanket. If too much Ar escaped, there would be a risk of suffocation.


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PostPosted: Mar 02, 2013 6:44 pm 
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FRE wrote:

Na for cooling does have it's problems, but the authors of Plentiful Energy, i.e., Till & Chang, believe that dealing with the reactivity of Na is a problem that can easily be dealt with. They provide examples. Even so, I'd think that it would be inconvenient. Surely it would complicate refueling since the entire operation would have to be done within an Ar blanket. If too much Ar escaped, there would be a risk of suffocation.


This is one of the advantages of the TWR vs SFR's, TWR pre-loads 40 years of fuel and shuffles it robotically without ever opening the vessel for 40 years.


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PostPosted: Mar 02, 2013 10:45 pm 
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Ed P wrote:
FRE wrote:

Na for cooling does have it's problems, but the authors of Plentiful Energy, i.e., Till & Chang, believe that dealing with the reactivity of Na is a problem that can easily be dealt with. They provide examples. Even so, I'd think that it would be inconvenient. Surely it would complicate refueling since the entire operation would have to be done within an Ar blanket. If too much Ar escaped, there would be a risk of suffocation.


This is one of the advantages of the TWR vs SFR's, TWR pre-loads 40 years of fuel and shuffles it robotically without ever opening the vessel for 40 years.


It remains to be seen whether the TWR will ever be practical. However, it is probably a good idea to continue work on any nuclear technology that seems promising. Work on the LFTR and IFR was prematurely halted and either would probably be better than our PWRs. It may be that TWRs will have a place.


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PostPosted: Mar 03, 2013 12:45 am 
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Ed P wrote:
So, basically this is a Na IFR, but much bigger because they load all the fuel in at beginning of life (and pay for it then, i.e. one of the problems with current PWRs is initial cost). This is especially costly for a fast reactor.

This would seem to require a massive Na inventory as well. Coolant is flammable and reacts with water.

Many coolant flow paths are a nightmare and require extra pumping power.

They have refueling shutdowns just like PWR's or normal IFR's, they just don't open the Reactor.

They have massive burnup and neutron fluence problems to overcome, with several work arounds like metalic fuel, sodium filled cladding, vented fuel (not too happy about that one). This is the reason I prefer LFTR's, even higher burnup, but no fuel damage concerns.

They keep the spent fuel inventory around the core and keep it activated, so any accident scenario would include it.

The design is still going through significant changes from candle TWR, to pebble in a pond TWR, to standing wave by shuffling fuel. Technically, CANDU is a standing wave reactor with water instead of sodium.

We have been working with fires for millenia but they also need fuel and ashes adjustment in case of solid fuel frequently. We know less about fast reactors.
Maybe if you have good reflectors on five sides and fertile uranium or thorium on sixth, it may work. You also have to constantly extract the heat and maintain the configuration for entire working life of the reactor.
It might be simpler with better control to have a molten salt core which can be easily reprocessed and metallic thorium as blanket, which can be reprocessed by electrolysis. The recovered U-233 can be just added to the liquid fuel periodically till it needs to be reprocessed in one or more decades.


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PostPosted: Mar 03, 2013 2:17 am 
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I have a different viewpoint toward the Traveling Wave Reactor. Bill Gate is pushing the Traveling Wave Reactor probably not because of its merit, but of the patents of the work from TerraPower that he can own. He is pushing it simply because of the newness of its ideas. The constant shifting of ideas will just mean more patents for him!

Whereas the MSR being an old idea he can hardly patent anything worth his time. Steve Jobs has rightly criticized Bill Gates' work as having no beauty. Bill Gates is tenacious but his products are pedestrian.

T. Wang


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PostPosted: Mar 03, 2013 3:01 am 
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EnergyUser wrote:
I have a different viewpoint toward the Traveling Wave Reactor. Bill Gate is pushing the Traveling Wave Reactor probably not because of its merit, but of the patents of the work from TerraPower that he can own. He is pushing it simply because of the newness of its ideas. The constant shifting of ideas will just mean more patents for him!

Whereas the MSR being an old idea he can hardly patent anything worth his time. Steve Jobs has rightly criticized Bill Gates' work as having no beauty. Bill Gates is tenacious but his products are pedestrian.

T. Wang


And his operating system is troublesome, unstable, crashes often, and is subject to hacking. That's why I have an I-Mac.

Years ago, I actually lost a job because the company for which I was working lost a huge amount of money because of problems with the Microsoft software; Microsoft showed no interest in fixing the problems. Not that I can blame William Gates personally.


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PostPosted: May 19, 2013 12:57 pm 
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TWR to use vented fuel..... (can molten salt fuel be far behind ? ....prefertably DFR, with lead cooling ?)

“TP-1 uses proven technologies for most of the plant with a few notable exceptions. The fuel pins are designed to vent fission product gases to the primary sodium coolant in a controlled manner. Venting the fuel pins enables deep burnups required to sustain the core for over 40 years and greatly reduces the probability of cladding failures.”

“One difference from previous fast reactor operation is the venting of fission gases from individual fuel pins described in the Design Description section. The primary consequences of venting have been identified as a small amount of 137Cs and 134Cs in the primary sodium coolant and 85mKr in the argon blanket gas. The cesium isotopes are continuously removed from the sodium with reticulated vitreous carbon traps and stabilized when the traps become saturated. The krypton gas is initially collected on cryogenic carbon beds and pumped to high-pressure storage vessels. These storage systems become distributed radioactive source terms in the reactor safety analyses. No significant engineering problems have been identified for fuel venting or the systems required to maintain the primary coolant and blanket gas at levels similar to unvented fuel conditions.”

http://terrapower.com/uploads/docs/ICAPP_2011_Paper_11199.pdf

Conceptual Design of a 500 MWe Traveling Wave Demonstration Reactor Plant
Proceedings of ICAPP 2011
Nice, France, May 2-5, 2011


Table 1 Key General Requirements

General Requirement
Parameter
Plant Design Life 40 years
Core Life (eff. full power years) 40 years
Core Thermal Power 1200 MW
Plant Availability (avg. over 5 yr) 90%
Site Seismicity (IAEA SL-2) 0.15g
General Safety (IAEA Document) NS-R-1
Safety Analysis (IAEA Document) NS-G-2.1
Construction Time 48 months


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PostPosted: May 19, 2013 4:00 pm 
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Apparently the TWR requires pumps and other components to operate reliably, without fail, and without maintenance, for 40 years. That seems to be expecting a bit too much.


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PostPosted: May 19, 2013 5:48 pm 
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FRE wrote:
Apparently the TWR requires pumps and other components to operate reliably, without fail, and without maintenance, for 40 years. That seems to be expecting a bit too much.

Quote:
The RVACS has sufficient capacity to remove the peak decay heat requirement that occurs about 24 hours after shutdown. RVACS has no moving parts and requires no operator actions.


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