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PostPosted: Feb 09, 2015 7:24 pm 
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Energy demand is now so high that serial production benefits will be available even with 1-2GWe units.
Hundreds/thousands can still be built.


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PostPosted: Feb 09, 2015 9:57 pm 
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The key is not serial production, but assembly line production.
Suppose you built a car in Detroit. Then you pulled up stakes
and built a 2nd, car, exactly the same, in S Carolina,
then you pulled up stakes and built the same car in California, and so on.
The productivity would be orders of magnitude worse than on as assembly line.
And quality control would be far more difficult.

Unlike cars and airplanes, nucelar power plants are too big to be built
entirely on an assembly line. Shipyards have the same problem.
So they build 500 ton plus blocks in a near assembly line environment.
At the last step they assemble these block in a building dock.
As a result, they can build a very large complex ship:
piping, wiring, engine room, everything for about 10 man-hours
per lightweight ton.

This is the only possible route to productivity and quality control for NPP's.
But to make it work you need to produce very large blocks
in your controlled environment. The good ship yards expend
95% of their labor at the block and earlier stages, only 5%
in the actual erection. We must have similar numbers.

Technically, ThorCon is an SMR, but we do not buy
the small is beautiful argument. early on we accepted as a constraint
that the blocks cound be no more than 23 m wide. This gets
us well up most major rivers inthe world and thru the Welland canal
and into the Great Lakes. Working backwards with some margins,
and a 4 year graphite life we ended up with a 250 MWe module.
If we could figure out how to get more power out of this envelope
we would. And eventually we will. ThorCon aspires to be a Big Modular reactor.

With respect to graphite life, if we went for a longer life
not only would we be far more vulnerable to unpleasant surprises,
much less flexible in feeding improvements to the fleet,
but thanks to the block size constrant, we'd end up with
less power per module.


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PostPosted: Feb 09, 2015 11:20 pm 
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As I understand it the reference 1000MWe DMSR core (with 30 year graphite life) is only 10m in diameter (so I assume the 23m wide thing is a typo?).
You could reasonably easily ship the core as a cylindrical module if you put the Primary Heat Exchanger on the top of it.

10m wide could be delivered on a barge quite easily, could always put a PCHE on top of the core if necessary to keep the length down - but since I mostly consider coastal sites we can move truly enormous objects around with relative ease. You could build a thousand megawatt primary loop and move it around.


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PostPosted: Feb 10, 2015 2:45 am 
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There does seem to be an issue with local production for the EPR.

Each installation needfrances new contractors for most of the work, who may or may not have the relevant experience. I think knowledge transfer from Finland, France and China is a key element of Hinckley C, so they're hoping to get some beenfits of serial production.

But producing 100 250MWe reactors in a factory is always going to be more straightforward than building 25 1GWe reactors out in the field. But a big cost might be the harbour spcially needed to unload the modules and the cost of that will scale with the volume of what needs unloading.

It might also be easier to ship to river locations. Thorcon has a 7m diameter reactor vessel, but a 21m wide boat to ship it. That's optimum for sea crossing, but what's the widest ship that you can get into, for example, Lake Michigan?


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PostPosted: Feb 10, 2015 2:56 am 
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macpacheco wrote:
The facts are well known, but it was very ballsy to poke the US NRC right on the eye. It seems they know they are in the USA but they don't expect to build the first one in the USA anyhow.


Where will the first one be built?

I'm not sure how adaptable the regulators are, but politically, Canada and the UK might be good. (See post on UK's CfD scheme)

In terms of demand, the Baltic States and Poland would love this technology, but they don't have much of a regulatory regime. The electricity grid in these areas is largely coal fired, so there are big environmental benefits too.


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PostPosted: Feb 23, 2015 7:18 am 
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I've been reading through the documents and some points / questions arise (sorry if repeating):

1. In the Offgas system (Exec summary, page 49):
Quote:
Virtually all the 137Xe and 90Kr will have decayed to 137Cs and 90Sr before the offgas leaves the OGR. These two particularly troublesome fission products will not show up in the offgas stream. Rather they will oxidize to fluorides and dissolve into the fuelsalt.


Wouldn't it be better to get these fission products out of the reactor into separate storage? After all, the Offgas system is designed to remove some, but not all, troublesome fission products. Why not get the Cs and Sr out while you can.

2. I'm still concerned about the depth of the silos, given the coastal / riverside location for the plants. How about evaluating:
- A six metre high silo hall - high enough for forklift / small crane access to pumps etc, and high enough to allow the secondary and tertiary heat exchangers to be above each other.
- A silo roof build in 8 segments (for a 4 reactor hall) that can slide (similar to some stadium roofs) to expose a can to the crane; or 9m diameter plugs in the silo roof that can be lifted by the main crane prior to can removal.
- A basic 20m high industrial building to house the crane, prevent water ingress, and provide a first layer of (sacrificial) defence to external threats. The silo roof obviously has to withstand the collapse of this building onto it.

Otherwise, I think you'd still need an over building to the keep water out (rain and floodwater, but then cover it in solar panels for a green halio :) )

3. ThorCon appears too reliant on manufacturing too much itself. I know it says "everything can be manufactured on a shipyard-like assembly line. But what should be outsourced? ThorCon's strategic advantage is what's in the Silos.

The starter shows:
Quote:
Starter 10 GWe/y Yard block diagram, 200,000 tons steel per year

In reality, the first plant is going to be 250MWe - maybe 1GWe. You can't justify a 800mx290m plant for that. So the first couple of Wall/Roof block lines will be bespoke projects - built by a ship yard between two container ships.

4. At some point, Thorcon might need smaller, specialist barges. The Big Rhine spec barge http://en.wikipedia.org/wiki/Classifica ... _Waterways has a draft of 3.5m and an air draft of 8.8m, which might just about fit a can of 11.8m height.

5. The costs don't cover decommissioning. In theory this should be covered by Can recycling costs, but if the cans are not recycled (base case), then it needs to be stored somewhere for 2,000 years. In the UK, nuclear pays a levy to cover this cost (the fund is massively underfunded, but mainly due to weapons, 1950s research, and old reactor designs).

6. Slide 45 in the "bob_sales.pdf" says looking for nation with
• Industrial capability
• Skilled workforce
• Waterside sites
• Rational regulator

Where's that? UK, Canada, S.Korea, France amongst developed nations? Otherwise China, Turkey, Brazil, UAE (but less IP protection). As I mentioned earlier, the UK's CfD scheme might provide the financial incentive for an investor. There's no reason why "reactor 1" couldn't get a guaranteed £150/MWh for its electricity.

All regulators are fixed on PWR and solid fuel systems, so would need top level pushing to become "rational", which might not happen in some countries.


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PostPosted: Feb 23, 2015 2:47 pm 
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Posts: 219
Location: Newport Beach, CA
djw1 wrote:
The key is not serial production, but assembly line production.
Suppose you built a car in Detroit. Then you pulled up stakes
and built a 2nd, car, exactly the same, in S Carolina,
then you pulled up stakes and built the same car in California, and so on.
The productivity would be orders of magnitude worse than on as assembly line.
And quality control would be far more difficult.

Unlike cars and airplanes, nucelar power plants are too big to be built
entirely on an assembly line. Shipyards have the same problem.
So they build 500 ton plus blocks in a near assembly line environment.
At the last step they assemble these block in a building dock.
As a result, they can build a very large complex ship:
piping, wiring, engine room, everything for about 10 man-hours
per lightweight ton.

This is the only possible route to productivity and quality control for NPP's.
But to make it work you need to produce very large blocks
in your controlled environment. The good ship yards expend
95% of their labor at the block and earlier stages, only 5%
in the actual erection. We must have similar numbers.

Technically, ThorCon is an SMR, but we do not buy
the small is beautiful argument. early on we accepted as a constraint
that the blocks cound be no more than 23 m wide. This gets
us well up most major rivers inthe world and thru the Welland canal
and into the Great Lakes. Working backwards with some margins,
and a 4 year graphite life we ended up with a 250 MWe module.
If we could figure out how to get more power out of this envelope
we would. And eventually we will. ThorCon aspires to be a Big Modular reactor.

With respect to graphite life, if we went for a longer life
not only would we be far more vulnerable to unpleasant surprises,
much less flexible in feeding improvements to the fleet,
but thanks to the block size constrant, we'd end up with
less power per module.


Jack -

I'm not so sure this is right. Serial production can capture nearly all of the economies of scale provided that:
1) All components are standardized
2) On site fabrication/completion is minimized
3) Work force turnover is minimized

Manufacturing in a single facility or shipyard is a sensible way to do this; it can also apply to on-site assembly, especially if you send the same workforce to each site. There are trade-offs with either approach.

The ThorCon approach makes me nervous in terms of public acceptance. Right now we can't even get right-of-way permits to move SNF from decommissioned reactors to a privately owned interim storage facility in Utah. That plan involved using rail through very sparsely populated areas and moving fortified dry casks. ThorCon will have to do the same thing on a frequent basis, only on barges in very active waterways and often highly populated areas. Are these NIMBY concerns justified, or necessarily permanent? Of course not, but it's a near-term reality. You'd have an easier time just leaving units on site, de-fueled, for the life of the plant.


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PostPosted: Feb 23, 2015 7:30 pm 
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Location: Montreal
Cthorm wrote:
ThorCon will have to do the same thing on a frequent basis, only on barges in very active waterways and often highly populated areas. Are these NIMBY concerns justified, or necessarily permanent? Of course not, but it's a near-term reality. You'd have an easier time just leaving units on site, de-fueled, for the life of the plant.

Yes, that can be a big problem.
Even if the regulator accepts your shipping plan, contingencies, etc.
In Canada, Bruce Power - currently the largest nuclear utility in the world - wanted to ship several used steam generators to Studsvik (Sweden) for steel recycling.
Those SGs are lightly contaminated on the inside, but all openings were welded shut.
The CNSC accepted BP's plan, even commending them for efforts to practice recycling.
But there was so much opposition from antinukes and frightened communities along the way (The St. Lawrence waterway), that BP gave up on it for the time being.
Not sure if it will ever get done.
Shipping used reactor cores and spent fuel would likely be more contentious, although SNF has been shipped in Canada on several occasions before (There is opposition now to shipping much larger quantities to a proposed Deep Geological Repository or DGR, whose location hasn't even been established yet -- we're still in the site selection process....)


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PostPosted: Feb 24, 2015 2:48 am 
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I know plutonium isn't easy to come by, but can we make a thought experiment if ThorCon could be powered by Plutonium + Thorium only.
If that were possible, let's think for a second:
No U238. As far as Uranium go, only U233/234/232/235/236 present. U236 concentration very low. U234 concentration fairly low.
I'm assuming in such a scenario, recycling core materials means just removing fission products. All Uranium and Transuranics fully recycled.

Assuming typical reactor grade plutonium, what would be the Pu to Th ratio ? How about weapons grade Pu ?
How much make up plutonium would be needed yearly per ton of Thorium ?

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PostPosted: Feb 24, 2015 3:36 am 
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Slide 29 shows fuel options:

http://prntscr.com/695ikw

It seems they need 5% fissile U-235.

Doesn't give % Pu. How does weapons grade Pu compare to U235 as a fissile material.


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PostPosted: Feb 24, 2015 4:07 am 
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alexterrell wrote:
Slide 29 shows fuel options:
http://prntscr.com/695ikw

That doesn't work for me. Error 522 - Connection timed out error from cloudfare
Quote:
It seems they need 5% fissile U-235.

Doesn't give % Pu. How does weapons grade Pu compare to U235 as a fissile material.


weapons grade Pu is worse than U235 as a fissile. Pu-239 makes 1.9 neutrons per thermal fission (67% fission probability), while U235 makes 2.2 neutrons per thermal fission (85% fission probability).

Let's assume they could use 5% Pu + 95% Th, instead of 5% U-235, 15% U-238, 80% Th-232.

With Pu+Th every fertile hit is making U233/232/234 (vast majority U233) which is a much better fertile even than U235 or Pu239. At startup there are no fission products, so very little neutron poisons. Then U233 concentration is increasing, while Pu concentration is dropping, while fission products are accumulating and competing for neutrons. So the more fission products are competing for neutrons, the more U233 fission we have (90% probability, 2.4 neutrons per fission). Breeding Pu from U238 takes more neutrons than produced by its fission, while breeding U233 from Th232 makes more neutrons than consumed (actually makes a net less than 2 accounting for neutron losses, but U238+Pu is even worse, if a net more than 2 neutrons were made, ThorCon would be a breeder, which seems impossible for a DMSR).

Weapons grade Pu means 95% or higher Pu239 concentration. Reactor grade Pu usually means fissile Pu239+Pu241 around 2/3.

Furthermore, the more U233 is made, the less make up Pu would be needed after reactor startup, specially with reprocessing.

This might allow ThorCon to compete for Plutonium disposition strategy pursued by the UK, while producing electricity much cheaper than S-PRISM, EPR or CANDU6.
A feature would be slow consumption of Plutonium, potentially enabling more DMSRs to be started with the same volume of Pu.

But my real point is Pu+Th fuel = no enrichment needed, Uranium is recycled back into the reactor. And pyro reprocessing is sufficient for reprocessing (remove only fission products). Since they are putting Thorium on the fuel, we might as well get some advantage from that.

The less Pu needed, makes reprocessing existing LEU SNF to obtain Pu more advantageous. I fully expect Pu+Th fuel to be more expensive than 5% U235, 15% U238, 80% Th.

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PostPosted: Feb 24, 2015 8:01 am 
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The lightshot link works for me, but otherwise slide 29 of this gives the proposed fuel mixes:

http://thorconpower.com/slides/bob_sales.pdf

The UK seems a good place to go. If they even consider a Sodium cooled reactor to dispose of Plutonium .....


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PostPosted: Feb 25, 2015 1:25 am 
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I found an article by Rod Adams in his atomicinsights.com blog that states Plutonium and U-235 have the same effect on a thermal reactor, same concentrations.
I'm going to assume he's simplifying it, meaning U-235 vs equal amounts of Pu-239+Pu-241 work the same.

So instead of 80% Th232 + 5% U235 + 15% U238, instead it could be:
93% Th232 + 7% weapons grade Pu (assuming this equals 5% Pu239+Pu241). If reactor grade Pu is used, it's likely it would be more like 90% Th + 10% weapons grade Pu.
But since Th232 is a better fertile than U238, in the long run this would improve conversion ratios, eliminate the need for re enrichment of Uranium in spent fuel, and reduce make up fuel needed periodically.

But those are the questions that only the actual nuclear engineers that understand how to simulate the ThorCon reactor could do, which is to tell us how much less Pu they would need, and confirm there are no downsides to this alternative.

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PostPosted: Feb 26, 2015 3:04 pm 
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Running Pu+Th is only for startup conditions. The thorium will become U-233 and with no U-238 in the mix you have an HEU core. We aren't volunteering to go fight the proliferation battle over this for commercial power plants. So, although it could be done there is no interest in engaging the political battles to make it happen.

As has been noted a plutonium fueled thermal machine will be a burner simply by the neutronics of plutonium even before you start getting realistic about reactor sizes, absorption by the salt, etc.


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PostPosted: Feb 26, 2015 3:34 pm 
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Lars wrote:
Running Pu+Th is only for startup conditions. The thorium will become U-233 and with no U-238 in the mix you have an HEU core. We aren't volunteering to go fight the proliferation battle over this for commercial power plants. So, although it could be done there is no interest in engaging the political battles to make it happen.

As has been noted a plutonium fueled thermal machine will be a burner simply by the neutronics of plutonium even before you start getting realistic about reactor sizes, absorption by the salt, etc.

Yep you're right, that's called removing the D from DMSR. Dummy me.
Proliferation can't be prayed away. But a country that has the Plutonium (even reactor grade) separated to begin with is unlikely to be interested in U233 for bombs.
Also it's a weird mix of U233/U234/U235/U236/U232 that isn't exactly weapons grade Uranium.
I wonder how LFTR will ever be possible then.
I have no expectation that Plutonium will make ThorCon into a breeder. DMSRs can't be breeders.
It was a though experiment. Obtaining Plutonium in industrial scale is a limited opportunity on a few countries that are serious about reprocessing.
Good luck and godspeed !

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