Energy From Thorium Discussion Forum

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PostPosted: Jan 04, 2014 6:29 pm 
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Three loops - wow! Do they all have to be molten salt? I can understand the concern about this stuff "rocking up." It would take a lot of heat to melt it. Ordinary heat or steam tracing wouldn't do. Any problem found with any of the loops would probably mean immediate shutdown and draining of the FliBe. It could be a real hassle to refill the steam generator so that it is solid (no air).

Would all three loops have to have separate cooling pumps? I would think that would be necessary. All of the FliBe loops would probably have to be constructed of exotic high temperature metal. The pumps would have to move that stuff pretty fast to cool the reactor and transfer the heat.

Well I guess the good thing is that with the cheapness of Thorium, some extra losses in the steam generator wouldn't matter too much. Coal plants have coal yards and ash handling facilities that take up quite a lot of room. I would guess the reactor could be constructed there in a separate building. This would allow for the higher level of security and containment of contaminating materials. Only insulated steam piping need exit.

How would the three loops be constructed physically? Would they be shell and tube heat exchangers looped together like chains or would the geometry be something where the heat is at the center and radiates outward to the various loops?

Three loops does sound like you would need the "economy of scale" to pay back the enormous capital cost. It might only work for the largest coal plants. They will be the last to be shut down.


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PostPosted: Jan 04, 2014 7:00 pm 
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I'm not optimistic about reuse of the steam generator. Even beyond there to the turbines and generators I suspect that once we have invested enough for a new nuclear plant and new steam generators we would pay the capital price to put in new generators as well if only to be comfortable that we won't get excess down time. Reusing things generally also means a custom design - something we definitely don't want.

The three loops would likely be molten salt but not all FLiBe. You might be able to reduce it to two loops but I'm thinking it is still new machinery. Certainly, one should look at reusing the site though. There is a fair portion of the costs involved with the transmission yard & lines, roads, railway lines, etc that one could benefit from.


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PostPosted: Jan 04, 2014 7:45 pm 
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I'm not suggesting to re-use the boiler tubes. I guess that would be the steam generator that you refer to.

Since there are no standard sizes any of these reactors is custom. Maybe 20 years down the road there will be standard sizes, but I see a long path before that happens.

I suppose it wouldn't help much if the reactor was a molten salt cooled Thorium pebble bed reactor. I'd guess that 3 loops would still be needed.

I suppose you are right about the retrofit. Sometimes recycling doesn't make sense. The idea of retrofitting the coal plant might be making a silk purse from a sow's ear.

It would be a way for the industry to develop. A lot of custom products will be needed for molten salt. Something needs to kickstart it.


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PostPosted: Jan 05, 2014 10:50 am 
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I did a little reading. It looks like water would be a better shield for tritium than more dense materials. This is counter intuitive. Will the molten salt reactor produce more Tritium than a light water PWR? Steam generators are what killed San Onofre. They are expensive to construct. They leak. Three loops would be much more expensive. The primary pressure would be lower but the fluid has to move fast and this will bring your pressure back up.

Maybe even the NRC would be reasonable and just allow continual sampling of the secondary loop. The water will be continually diluting the tritium. This dilution will bring the level to a little above background which should be an acceptable risk. This may allow two loops which is the existing technology.

Radon is little risk if you have a good ventilation system. Will a good ventilation system dilute tritium? The stuffs pretty light. Can it be vented out? Will the cooling water become more and more contaminated as the tritium displaces some of the hydrogen to form super heavy water? How much risk would we really be posing to the public? How would this compare to the heavy metals from the flyash of the coal plant or stack emissions? Which poses more risk to the public?


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PostPosted: Jan 05, 2014 10:58 am 
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Tritium becomes part of the water and makes the water "radioactive waste" that has ll sorts or handling requirements and limitations. You can't just dump it. The problem that TEPCO has with all those tanks of water is that even after they remove ALL the other isotopes, they are still stuck with tritiated water which they can't dump.

My suggestion is to take it to a stable glacier somewhere and freeze it into the glacier. There it can stay locked away from the biosphere for 120+ years till it decays away.

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PostPosted: Jan 05, 2014 6:43 pm 
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I guess you are right. The following link says it is more of a legal problem than a health problem. This link discusses PWRs and does touch on BWRs.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CE0QFjAD&url=http%3A%2F%2Fhps.ne.uiuc.edu%2Frets-remp%2FPastWorkshops%2F2008%2FSession%25203%2520-%2520Greg%2520Jones%2520-%2520Presentation.ppt&ei=i-fJUr5pxPjJAcvQgNAL&usg=AFQjCNFNVXkET8m1yJE67Mahd0mqkF7E8g&sig2=3WrjVnmHFZWeeZJH65Q79g&bvm=bv.58187178,d.aWc

This is a slideshow and may need special software to be viewed. It has a ppt extension. The postulated dose for contaminated groundwater found near nuke plants would give you .3 millirem a year if that was all you drank. This is .1% of the background radiation.

The given solutions are increased blowdowns in the steam generators and good ventilation. This is essentially dilution.

Does it have to be 120 years? 60 years gets rid of 97% of the stuff.

Maybe it is a good idea to put in an extra loop. If there are lots of reactors, there will be lots more tritium and lots more chance of it being ingested. Even then I wonder about the actual harm to the health and safety of the public.

How would the relative risk of this stuff compare to smoking or the use of bright colored Mexican pottery? I know. It's the law. It's for my own good ,....right?


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PostPosted: Jan 05, 2014 6:46 pm 
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I just thought of something in regards to KitemanSA's post. There may not be any stable glaciers good for 120 years. As ole Bobby Dylan (Robert Zimmerman), the times a they are a changin'.


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PostPosted: Jan 06, 2014 6:23 pm 
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Eino wrote:
I just thought of something in regards to KitemanSA's post. There may not be any stable glaciers good for 120 years. As ole Bobby Dylan (Robert Zimmerman), the times a they are a changin'.
Seems the Antarctic is growing which may not technically be "stable, but its good enough. And I suspect that glaciers on the north side of various arctic islands are also stable enough.

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PostPosted: Jan 06, 2014 7:04 pm 
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It would be a tough sell to "turn the pristine Antartica into a radioactive dump". That is a PR battle I would not want to attempt. Frankly, the best place for the treated Fukushima water is the ocean. But presuming that is not feasible one might make a large lake out of it. I hear there is some land available near Fukushima that likely doesn't have another use for quite a while. And yes this is all a legal and PR battle that has nothing whatsoever to do with health or wise expenditure of money for Japan when they need to be rebuild much of their country.


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PostPosted: Jan 07, 2014 5:50 am 
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Lars wrote:
It would be a tough sell to "turn the pristine Antartica into a radioactive dump". That is a PR battle I would not want to attempt. Frankly, the best place for the treated Fukushima water is the ocean. But presuming that is not feasible one might make a large lake out of it. I hear there is some land available near Fukushima that likely doesn't have another use for quite a while. And yes this is all a legal and PR battle that has nothing whatsoever to do with health or wise expenditure of money for Japan when they need to be rebuild much of their country.
A lake will evaporate into the biosphere quite quickly.

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PostPosted: Jan 07, 2014 12:57 pm 
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Properly we should calculate the rate at which tritium is released into the biosphere to see whether this is a concern in the first place - my bet is that it has no impact on public health.

But you are probably right that PR wise one must prevent this for three decades or more. So perhaps a cover over the lake or a surface chemical that substantially reduces evaporation?


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PostPosted: Jan 07, 2014 1:33 pm 
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You could also pump the water in a deep saline aquifer. They're quite ubiquitous, holding millions years old dense (not rising up) salt water. The cost would be limited to the cost of drilling down a deep well.


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PostPosted: Jan 07, 2014 2:00 pm 
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You could just store it in giant plastic tanks for 120 years.

Probably cheaper than all of the above.


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PostPosted: Jan 08, 2014 2:56 am 
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Freeze it into a glacier.

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PostPosted: Jan 09, 2014 7:42 pm 
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"Freeze it into a glacier."

Glaciers are not static. Glaciers are rivers of ice. How far will this glacier move in 60 years? Based on previous government action at Yucca Mountain, I don't think this would be easily permitted.

So - Three loops keeps the tritium out of the water for the most part. I take it that the second loop will be somewhat cooler than the first loop since the heat is to be transferred to it. The water in the third loop will be cooler yet, but still plenty hot enough to make the superheated steam for old Mr. turbine.

How big would the reactor be for old Mr. turbine? From Wikepedia:

The BTU is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in BTU required to generate 1 kW·h of electrical energy. A typical coal-fired power plant works at 10,500 BTU/kW·h, an efficiency of 32–33%.

So if it was 40 MW, would we need a reactor putting out 120 MW of heat? In terms of efficiency over the original boiler, have we gained anything? We will have three large sets of pumps to push fluid through our steam generator. We will not have Forced Draft fans, mills, ID fans, conveyors and much of the equipment it took to run our old coal plant. What would be needed for water chemistry and FliBe chemistry? Will the electrical needs of the Molten Salt Reactor be much less than that of the boiler which it is replacing?


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