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PostPosted: Jan 25, 2014 1:49 pm 
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There was the ~820MWe CANDU 9 design as welll.

You could even embrace that idea that is often floated for supercritical CANDU to insulate the inside of the pressure tube and dispose of the seperate Calandria tube entirely.
The increased strength (from the reduced temperature of the tube wall and from the fact that the calandria and pressure tube metal is now all available to the latter) would permit significant upsizing.

Additionally I am not convinced that a fluid fuel reactor in a CANDU design is really practical as there are no high uranium content liquids available that are molten under reasonable conditions.


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PostPosted: Jan 26, 2014 4:02 am 
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Sagging of tubes could possibly be handled by spacer-supporter frames.
Candu-6 and Indian 700MW PHWR are possibly the optimum design of multi-tube reactor. Bigger designs have not been economical.
Heavy PWR vessels are a specialized design and only a few places are there to build them. The submarine reactor will be too small for economical power production. 500MW-1GW is the optimum range of power plants with existing technologies. Heavier plants have been costlier. I think India will only erect heavier reactors if they can be imported.
It is time to develop new fuels and coolants for PHWR.
Partial use of thorium may be a good idea as per an Indian study. There are some Lightbridge studies too. Use of a thorium blanket as in Shippingport design could improve conversion ratios. It could possibly lead to a breeder or at least generate U-233 fissile for AHWR type thorium fuel.
Far from limitations, even the medium size PHWR could be a possible thorium breeder or near breeder.
I wonder if FNaBe coolant could work and what would be the preferable tube size for it?


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PostPosted: Jan 26, 2014 12:41 pm 
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Sagging of tubes is an almost trivial problem that is easily solved by standard industrial practise.

Jaro's response assures my argument that there are no technical grounds for the lack of large PTRs, only political and business ones.

Having a double CANDU 6 in one containment seems like a pretty good way around the problems, though.

I'm also with E. Ireland in the internal insulated fuel channel concept. I'm a big fan of internal insulation. It is widely used by the fossil fuel industry to insulate hot ducting and such. Such simple innovations are widely used in the fossil fuel industry, but take 50 years or more to be adopted in the ultra conservative nuclear industry that has (sadly) been bullied into such ultra conservatism. Some plants are actually in trouble because of this - here in the Netherlands, our only nuclear powerplant has had issues with old fashioned circuitry which were unvailable on the market. Its like having MS-DOS as your controlling software and having to buy floppy discs. Suppliers would simply laugh at you or give you a blank.


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PostPosted: Jan 26, 2014 3:53 pm 
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jagdish wrote:
Candu-6 and Indian 700MW PHWR are possibly the optimum design of multi-tube reactor. Bigger designs have not been economical.
In Ontario there are currently 10 larger Candu reactors in operation: four 870MWe units at Darlington, and eight 750/830 MWe units at Bruce A/B.
These supply most of the ~60% of electricity in the Province, that is derived from nuclear (the smaller Bruce A units could also supply >800MWe, but were originally equipped with smaller turbines, because some of the steam was used for the Bruce Heavy Water plant, which has long since been decommissioned...)
Except for hydro (3.5¢/kWh) nuclear is also the cheapest (5.6¢/kWh).

http://media.cns-snc.ca/ontarioelectric ... icity.html


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PostPosted: Jan 28, 2014 1:34 am 
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I stand corrected.


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PostPosted: Jan 31, 2014 7:48 pm 
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Bear in mind though that Ontario's Bruce and Darlington units are going in for refurbishment which has turned into a nightmare with staggering cost inflation.

These CANDUs have cost Ontario a mint and the refurbishments are going to be a real nightmare.


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PostPosted: Feb 01, 2014 11:42 am 
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rban wrote:
Bear in mind though that Ontario's Bruce and Darlington units are going in for refurbishment which has turned into a nightmare with staggering cost inflation.

These CANDUs have cost Ontario a mint and the refurbishments are going to be a real nightmare.


It isn't the fault of CANDU though. In a fossil fired plant, retubing a boiler costs under 0.1 billion. Retubing anything in a nuclear plant quickly ends up in the billions. Its one of the biggest mysteries in the economics of nuclear power for me. Crazy levels of bureaucracy and quality control are certainly a factor, but even then its crazy. Try spending several billion dollars. Its hard even if your goal is to spend as much as you can. Hire expensive $500/hour people, well it takes two MILLION hours of such fancy labor to get a billion dollars.

Where's the money sink? Who is getting richer than God? We discussed this extensively on previous occasions here and in other forums/blogs. Still no clear answer.


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PostPosted: Feb 01, 2014 12:53 pm 
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The cost inflation for the Darlington units was so enormous that it would almost be cheaper to build new CANDUs and transfer the heavy water.
It really was absurd.


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PostPosted: Feb 01, 2014 1:04 pm 
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E Ireland wrote:
The cost inflation for the Darlington units was so enormous that it would almost be cheaper to build new CANDUs and transfer the heavy water.
It really was absurd.
I presume you mean Pickering or Bruce, because Darlington hasn't been refurbed yet.
As for Bruce, that refurb was done by a private company - based on an agreement with the Province for a 7.5 cents/kWh guaranteed electricity price.


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PostPosted: Feb 06, 2014 11:45 am 
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jaro wrote:
E Ireland wrote:
The cost inflation for the Darlington units was so enormous that it would almost be cheaper to build new CANDUs and transfer the heavy water.
It really was absurd.
I presume you mean Pickering or Bruce, because Darlington hasn't been refurbed yet.
As for Bruce, that refurb was done by a private company - based on an agreement with the Province for a 7.5 cents/kWh guaranteed electricity price.


Pickering reactors (six left) are to be shut down by 2020. Bruce has eight reactors, 4 of which are to be shut down by 2018 and the other four have been refurbed (at enormous cost inflation).

The debate in Ontario right now is what should be done at Darlington. There are four reactors there. Build new reactors? Refurb the four that are there?

On top of that the one remaining CANDU in Canada at Pt Lepreau had huge cost inflation in its refurb as well.

Not a pretty picture at all.


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