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PostPosted: Sep 16, 2016 11:53 pm 
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jaro wrote:
The problem with the "tube-in-tube" idea was a very high aspect ratio -- about 8 : 1 as I recall -- which is fine in elementary point reactor theory, but says nothing about the real world. In the real world, that thing would oscillate like crazy, causing vibrations that would shred it to pieces in a day or two.
I want to know more about this oscillation problem. Where should I look?


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PostPosted: Sep 17, 2016 12:12 am 
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What I'm saying is that I strongly suspect an LEU-fueled MSR can't outperform a CANDU, or maybe even an LWR.


If that is true then it suggests Terrestrial Energy have seriously miscalculated. They claim it will use 1/6 the fuel of a LWR.

But even if they used the same amount of fuel as a LWR they would still likely be a worthy improvement. On paper at least the IMSR looks much cheaper to build and safer to operate compared to a LWR like the AP1000. And fuel recycling for an MSR should be simpler.


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PostPosted: Sep 17, 2016 8:00 am 
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BSFusion wrote:
I want to know more about this oscillation problem. Where should I look?

The problem arises even with large, ordinary reactors, where the total amount of "lattice units" (fuel + moderator) is many times the minimum for criticality.
But it is much less severe and readily managed, because the solid fuel is segregated from the moderator, which tends to dampen combined flux-thermohydraulic effects -- in contrast to MSRs, where things may be more intimately mixed (especially types without graphite or other solid moderator, or external moderation only).
Also, the risk is magnified with extreme aspect ratio -- both because the total amount of fuel salt is well above minimum for criticality (as compared to low aspect ratio cylinder or sphere), and because such configurations provide a nice resonance chamber for oscillation (think of an organ pipe and acoustic oscillations).
Another way to magnify the risk is by increasing compressibility of the fluid, for example with the presence of bubbles of fission product gases and vapors like Krypton, Xenon and Tritium, as well as Helium introduced on purpose to scavenge the FP gases.
The most extreme case would of course be a gaseous or vapor core reactor with extreme aspect ratio: In the 1950's there was in fact a concept for a strongly oscillating reactor that would extract electric energy by magneto-hydrodynamic means, as a shockwave passed several times per second from one end to the other, while interacting with coils wrapped around the cylinder.
The oscillation was of course driven by compression and fission power bursts at each end of the long cylinder, as the shockwave hit the end wall.

In commercial nuclear power, issues like neutron flux oscillations are generally handled by teams of reactor physics analysts working for the Company that designs and builds the plants.
So most of it is proprietary IP.
Not sure if you could find any textbooks or graduate-level courses that deal with the matter.

On a simpler level, there is much publicly available material on the subject of power-driven acoustic oscillation in fossil fuel burning furnaces, and also in rocket engines (rocket engines designed without careful attention to acoustic oscillation will explode within seconds of ignition...).


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PostPosted: Sep 17, 2016 1:04 pm 
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Im tempted to determine if a SEU fueled load under power reactor cooled with boiling light water and moderated with heavy water would achieve decent economics. Load under power is much more developd than it was when they attempted Gentilly 1 thanks to endless Magnox/ AGR and CANDU experience.


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PostPosted: Sep 18, 2016 7:35 pm 
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Kirk Sorensen wrote:
The reason all these companies don't "get together" is because they all see the go-forward strategy differently. That's ok. But that's why they don't "join forces" and that's why there are so many disparate concepts.


I would not want all these companies to join forces either. LFTR, IMSR, and WAMSR all solve different problems. Or, perhaps, they all solve the same problem of energy production but with different compromises. I can see a future where all of these technologies, and more, coexist because different parts of the world have different compromises to make.

I like Dr. LeBlanc's IMSR as it solves a problem of providing energy to remote locations in a way that has low risk of weapon proliferation and environmental impact. In this case a loss of performance over more complex LWRs may be acceptable. Even if used in a large power plant closer to "civilization" this may be acceptable because of the inherent safety of the design. I believe I understand Mr. Sorensen's concerns of enriching the fuel and only have it diluted again when used to "top off" an IMSR. The waste produced may be a problem but, again, this may be acceptable because of other concerns. IMSR and LFTR do have an overlapping market but the market is not completely coincident.

Some concern was mentioned on the absence of Dr. LeBlanc and Dr. Dewan from this forum and I have my own theory. The IMSR is primarily a uranium burner, while thorium has been mentioned as a potential fuel I get the feeling from recent interviews with Dr. LeBlanc that this is not a primary selling point for the design. While I miss reading Dr. LeBlanc's posts here I cannot blame him for not coming here more often. This site is dedicated to thorium as fuel but Dr. LeBlanc wants to sell uranium burners, he may simply feel this site is a poor fit to discuss his designs. It's also quite possible he's just busy.

I also believe much of the same applies to Dr. Dewan. She's likely quite busy. The WAMSR does not use thorium as its primary fuel. I do believe she would be welcome here but this is a site dedicated to discussing energy from thorium, while WAMSR is dedicated to deriving energy from nuclear waste. She may have a lot to discuss on this forum but it may not be a good fit for her time and effort.

I've seen pictures of Mr. Sorensen, Dr. LeBlanc, and Dr. Dewan all together and not biting at each other and gouging out eyeballs so it seems they can get along just fine, at least when the cameras are around. There's room to collaborate and it seems that to some extent that they do by appearing at the same conferences and I'm sure more. In another way they do compete and I prefer it that way, may the best design win. Assuming there is a way to "win" in this competition.

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PostPosted: Sep 19, 2016 9:57 pm 
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The following document from 1980 has some interesting information on the DMSR design and make up fuel. In particular table 17 on page 31. It shows that the fuel is originally LEU at 20% U235. In years 1, 2 and 3 all that is added is U238 to ensure that the fuel mix does not become too fissile (ie denaturing). It's not until year 4 that they add more fissile. The figures on page 30 are also worth looking at as they show that the power output of the DMSR would vary over the life of the plant based on the changing fuel mix.

http://moltensalt.org/references/static ... M-7207.pdf

It's worth stating that the DMSR and the IMSR are not the same beast. The DMSR described in this document has a 30 year life whilst the IMSR has a 7 year life.

The paper does also somewhat confirm one suspicion that I had. Which is that both the IMSR and the DMSR can probably operate beyond their nominal life if operated at lower average power levels. This could be useful if you buy and IMSR600 but only ever need 400MWth.


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PostPosted: Nov 25, 2016 5:18 pm 
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macpacheco wrote:
Kirk Sorensen wrote:
I don't think the IMSR can outperform a CANDU in terms of energy extracted from a unit of natural uranium. Refueling of the IMSR will inevitably lead to a large loss of separative work, and extraction of equilibrium fuel will also result in a loss of separative work.

Solid fueled reactors can remove uranium fuel at enrichments below the average enrichment level of the core. Molten salt reactors, at least those with a single fluid, do not appear to be able to do this. Thus a lot of uranium will be wasted in an IMSR.

Molten-salt reactors offer much more potential when the fissile and fertile materials are chemically distinct. When they are the same (such as in the LEU case) they appear to run into real problems with their fuel cycle.


1 - The most critical aspect with new nuclear is cost / MWe until the revenue starts coming and and time until the revenue starts coming in. If IMSR costs 1/2 of an LWR and 1/3 of a CANDU, most of your arguments are quite mute from a real world business perspective, and we all know, fuel costs are tiny compared to initial investment.
2 - How much make up fuel will be added / year vs startup fuel ? Depending on how much / how little, that loss of separative work could be quite acceptable
3 - How about all of those neutron efficiency gains with having far less neutron poisons in the reactor core, the advantage of having a fairly homogeneous fissile to fertile ratio throughout the operational life of the reactor ? Those advantages help all MSRs. Why wouldn't those advantages offset the disadvantages you claim would be show stoppers ?

PS: I'm not claiming an IMSR will actually cost 1/3 of a CANDU and/or 1/2 of an LWR, but since you took the job to attacking Terrestrial by questioning the data they can't publish since they feel its valuable, I think somebody should suggest some data point at some more optimistic to balance the argument.


My understanding is that fuel makes up a relatively small amount of even operational costs, nevermind the cost of initial investment ( and insurance based on long build times ).

From what I've heard and read about IMSR it should have a fairly easy time getting less cost per MWe in generation, especially if we're limiting scope to Western designs. It would actually be interesting to know just how much money would have to be spent on fuel and waste management to neutralize the advantage of halving the capital costs and workforce ( simpler passive safety suggests that staff on site should go down as well after all).

Edit:

Just to quantify this a bit more the AP-1000s in the US seem to be coming in at around 7 billion each. You'd need the largest IMSR to come in at less then 1.75 billion to beat capital costs at which point it starts to become economically attractive. How realisitc or not is that?


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PostPosted: Nov 27, 2016 12:13 am 
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The Canadians wisely went ahead for hundreds of pressure tubes when there was a problem of heavy engineering for reactor vessels. Now that they have more uranium than they can sell, it is quite logical to go for lower capital cost reactors. They may not be interested in breeders.
IMSR may be a good choice for them.


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PostPosted: Nov 27, 2016 12:55 am 
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It appears that new build CANDUs may be back on the agenda - Ontario Hydro has recently increased its estimate of its required quantity of reactor grade heavy water to allow for two new units, and with all but two of its reactors operating it appears the nuclear output drought is over. [The two that are still shut down are Pickering A units that were written off before the other units were overhauled and returned to service]


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PostPosted: Nov 27, 2016 6:30 am 
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Amur_Tiger wrote:
My understanding is that fuel makes up a relatively small amount of even operational costs, nevermind the cost of initial investment ( and insurance based on long build times ).

From what I've heard and read about IMSR it should have a fairly easy time getting less cost per MWe in generation, especially if we're limiting scope to Western designs. It would actually be interesting to know just how much money would have to be spent on fuel and waste management to neutralize the advantage of halving the capital costs and workforce ( simpler passive safety suggests that staff on site should go down as well after all).

Edit:

Just to quantify this a bit more the AP-1000s in the US seem to be coming in at around 7 billion each. You'd need the largest IMSR to come in at less then 1.75 billion to beat capital costs at which point it starts to become economically attractive. How realisitc or not is that?


Conceptually if the core is 100% factory built and shipped in a single module and is substantially simpler than water cooled reactors, combined with thermodynamic efficiency around 50% (less thermal power produces same electricity), the concept does have a lot of potential.
The basic advantages of an MSR, combined with Dr LeBlanc extreme KISS design approach should succeed.
Unfortunately Terrestrial has been quite silent about the details for a design that could be submitted to the CNSC for approval in a year or two. They have little to gain by divulging their latest design choices and a lot to loose as competitors pick apart their design, trying to find problems everywhere (real or not).

I can only hope that CNSC actually makes their life substantially easier than NRC certification. Its one thing to offer an easier certification path, but until a vendor actually gets final approval, we can only hope that path will actually be substantially easier. They can always invent pot holes along the way, like the NRC does all the time.

I suggest studying on public general MSR advantages. Those substantiate a lot of reasons why Terrestrial should succeed. Fingers crossed.

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PostPosted: Nov 27, 2016 9:20 am 
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E Ireland wrote:
It appears that new build CANDUs may be back on the agenda - Ontario Hydro has recently increased its estimate of its required quantity of reactor grade heavy water to allow for two new units, and with all but two of its reactors operating it appears the nuclear output drought is over. [The two that are still shut down are Pickering A units that were written off before the other units were overhauled and returned to service]

If the new CANDU's use Thorium-LEU fuel as in the study for Indian ahwr-leu, it could
1. Produce more power per tube
2. Have longer fuel life.
https://drive.google.com/file/d/0B6OcA2 ... wYzlk/view
Vertical tubes are not necessary.


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PostPosted: Nov 28, 2016 10:20 am 
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E Ireland wrote:
It appears that new build CANDUs may be back on the agenda - Ontario Hydro has recently increased its estimate of its required quantity of reactor grade heavy water to allow for two new units, and with all but two of its reactors operating it appears the nuclear output drought is over. [The two that are still shut down are Pickering A units that were written off before the other units were overhauled and returned to service]


I wonder how much of that has to do with a desire to keep a lot of nuclear power on the grid when they're doing their overhauls.


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PostPosted: Jan 25, 2017 3:00 am 
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Quote:
TERRESTRIAL ENERGY PUTS NRC ON NOTICE: 2019 ADVANCED LICENSE SUBMITTAL COMING

IMSR seems to be proceeding well. It will not be a breeder but it could be the first commercial MSR.
Addition of a metallic thorium blanket in later versions could provide the necessary additional fissile in form of superior fissile U-233.


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PostPosted: Jan 25, 2017 5:34 am 
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Not a breeder but 4x the burnup of PWR/LWR with lower enrichment levels plus 50% turbine efficiency.
Enough to replace every coal/gas/oil/old nuclear plant with IMSR and keep the same uranium mining and enrichment facilities.
I think they deserve far more love.
The real bottleneck is getting the first MSRs to market and make water cooled reactors 100% obsolete.
Once GE/Westinghouse/Areva/... gives up on doing water cooled reactors and start looking for MSR as the future, everybody that's doing MSR design today will have a job and great funding (if they want to submit to big corporations).
If Terrestrial fails, likely all MSRs fail, cause they're the only effort that is truly KISS based no ideology, just pragmatism.
Less dreaming more results, please !

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PostPosted: Jan 27, 2017 3:57 am 
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http://www.world-nuclear-news.org/NN-Te ... 11701.html

Quote:
Terrestrial said it intends to start "pre-application interactions" with the regulator this year and to make its licensing application in late 2019


How long will US regulatory approval take?
We could perhaps see this approved in 2024, and operating in 2027?

Terrestrial might have to choose where they focus, with efforts in Canada, USA, and the UK.


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