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PostPosted: May 30, 2015 12:31 pm 
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During the last couple of weeks I studied the effect of the new additive manufacturing methods on MSR reactors. I`m sure if these methods will become more advanced in the following years and decades they will make the manufaturing of an MSR easier and might become a game changer.

Additive methods as EBM have the advantage that no molds or tools only a 3D CAD file is required. No material is wasted. On the other hand these technologies have a low productivity and accuracy. Hence EBM/SLM is widely used in manufacturing prototypes. The production numbers of nuclear power plants are small. A successful manufacturer as ROSATOM sells in average 1 - 2 plants/yr. working on each of them 5 – 8 years. Even a strong renaissance of nuclear energy will most probably not increase the yearly new orders for big power reactors above 10/manufacturer/year. Mass manufacturing seems unrealistic. The numbers produced are similar to the prototype manufacturing of other businesses.

My study concentrated on molybdenum alloys as it is the preferred material for chloride salt reactors where I see the biggest opportunities. The late fluoride salt reactor designs as the French/European MSFR are designed for temperatures where the foreseen nickel alloys are at its limits and might be overchallenged in case of an accident with some temperature increase due to the decay heat. Hence it would be an asset to use molybdenum alloys at least for some critical components of a MSFR as hx as well.


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PostPosted: May 31, 2015 3:54 pm 
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Thanks Holger,

MSRs tend to be smaller and based on production line technology, rather than 1 offs.

So for a 500MWt heat exchanger, could EBM make 50 units per year. If say the current HX weighs 10 tons, the EBM one will be lighter.

The PHX is a major source of low level waste, so if this can be lightened that is a major positive.


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PostPosted: May 31, 2015 4:16 pm 
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Dear Alex,

a LWR needs to have at least 1000 MWe to become somehow competitive to a coal fired power plant. Acc. to NEI (2013) total operating cost nuclear 2.3c/kWh vs. coal 3.2c/kWh which means there is an advantge of max. 71 Mio. $/year to compensate the higher capital Investment.

The complexity of a MSR is due to the internal fuel treatment (it needs to have at least a degassing, separation of fp with low bp and a separation of noble metal fp) higher than that of a LWR. It uses super alloys instead of steel (LWR). The capital investment is higher. The fuel costs might give on the other side a cost advantage of 0.4c/kWh or 32 Mio. $ for a 1000MWe plant.

If you plan to stay somehow in reality it will require at least a block size of 2000 MWe for the MSR to become cost competitive vs. LWR and coal.


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PostPosted: May 31, 2015 5:09 pm 
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HolgerNarrog wrote:
If you plan to stay somehow in reality it will require at least a block size of 2000 MWe for the MSR to become cost competitive vs. LWR and coal.


What do you mean by "block size"? Can the economies of scale be achieved with multiple smaller (100 MW perhaps) reactor cores running in parallel? This way the cores could be made assembly line style and as a possible proof of viability of small modular reactors?

If someone plans to do a 3D print of a reactor then it would seem that making multiple smaller parts would be easier than one large part. The printer would not have to be as large. If there was a part that did not meet specification after production then it could be recycled to try again, it would be a loss but not near as much as a single 2GW core.

Forgive me if these are rather naive questions. While I am an engineer I don't deal with concrete and steel, only bits and bytes.

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PostPosted: May 31, 2015 6:07 pm 
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There is no reason you can't pump out a 2000MWe block on a production line.

They produced Liberty ships on what amounts to one.


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PostPosted: May 31, 2015 9:41 pm 
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Well, they tried to build LWR power barges/power blocks in Florida, but that didn't pan out due to economic factors. Only things left were the big drydock and port upgrades, as the big crane for doing superblock lifts got disassembled and sold to a chinese shipyard. Mass production really only kicks in at either large dimensional size or large quantities, which means you are looking at 100MWe class truck transportable blocks, or a power barge shipyard creating reactors greater than truck transportable in size.

The russians with their LWR power barge are a modern take, and considering the joint work Rosatom is doing with the chinese, it isn't a big jump of logic to see them doing something similar. Imagine chinese mass produced nuclear power barges, leased to african countries who are already receiving large port upgrades underwritten by chinese banks and chinese government economic development assistance. The kicker being the powerplants can be repossessed if their "preferred partner" client state gets out of line. Imagine an ACPR-1000 on a barge being "exported" folks.


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PostPosted: Jun 01, 2015 2:27 pm 
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Dear Kurt,

you can split the costs of a nuclear power plant in the categories

One Time Costs:

Basic design, design approval, molds and tools, certification of manufacturing companies

Costs that are independent from the size:

Site approval, infrastructure as roads parking.., instrumentation & controls, testing & documentation (a large joint of costs)

Costs that increase underproportional with the size

Mechanical construction, civil construction, turbines and generators, emergency diesels....as the volume grows in the 3rd dimension most manufacturing costs grow strongly underproportional. When I made some rough designs of MCFR it needs only a few cm more to increase the power by x%.

All in all the costs of power plants and as well nuclear power plants grow strong underproportional.

The size limits are set by the grid operators. Grid operators does not appreciate too big units because it can cause trouble in case of a break down or maintenance period. The today`s comfort zone for grid operators is limited at about 1200 - 1600 MW. It increases step by step with the expansion of the grids.


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PostPosted: Jun 01, 2015 5:44 pm 
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HolgerNarrog,
Excellent explanation of the costs in building a nuclear power plant but my original question remains, what is meant by "block size"? Does the "block" refer to the individual reactor core or the entire power plant which may have several reactors on site?

I hear a lot of talk about the advantages of small modular reactors and how MSRs are a good fit. If the one time costs of site approval, design, tooling, etc. can be done to make a 1200 - 1600 MW power plant made up of multiple cores, each with an output in the 100 - 300 MW range then would this not do a lot to reduce costs for the planned power plant and future power plants that follow?

What I mean is that if the one time costs can only be justified with a power plant of a size greater than 1000 MW then a forward looking engineering firm might use this as an opportunity to develop and prove small modular reactors so that a business case can be made for smaller, and more easily sold, power plants. Once a reactor core is approved by the powers that be I'd expect getting the same design approved for another site would be much less costly, as a lot of the work has already been done. A "big" plant (1500 MW class) design can be translated into a "small" plant (150 MW class) by going from ten cores to one.

As E Ireland points out the mass production of large structures has been done. As I recall the tools used to produce the Liberty ships still exist and are in use today. The need for these massive presses and dies is such that no one wants to build more or any bigger, and the function they perform is something so basic that new technology does not offer enough advantage to replace them with something new. Question then becomes, have we seen a new technology that can finally obsolete this century old tooling? Can additive manufacturing make large structures as easily as small ones? I've seen claims that people have figured out how to "print" houses. It looks like EBM and SLM technology cannot produce such large structures today but I see no reason that it can't be used to make something of any size. It doesn't have to be the size of a house but something like a 200 MW MSR reactor core could, if the claims of small modular reactor advocates are correct, make for a profitable business.

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PostPosted: Jun 01, 2015 8:38 pm 
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A licensing based cost problem is that currently multiple cores require multiple control rooms. If you had multiple install of 100MWe SMR's at equivalent net output to a large plant, you are looking at 8 or more cores at least. The ops cost for that many control rooms alone would be painful. If NRC or other licensing bodies would allow a unified control room for plants featuring multiple cores of the same or very similar type, then the cost calculus for introducing SMR's in large builds becomes reasonable, providing a backdoor to SMR development.


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PostPosted: Jun 03, 2015 12:05 pm 
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Dear Kurt,

the productivity of additive manufacturing is extremly low. If you can produce 1 - 2 mm/hour it might need 1000 h to make a m piece (A bigger machine with a larger work chamber and a larger eb System would be required). I would use these methods for pieces only that are difficult to make by established methods of manufacturing.

Example: The hx of a MSR should have very small channels to minimize the quantity of fuel out of the reactor and the dimensions of the hx itself. A potential manufacturing method with some limitations is diffusion bonding. For this purpose EBM is a great opportunity.

Example2: The reactor vessel is a huge piece of metal that can be manufactured by casting, sintering and welding pieces together. It is most probably more economic to stay with the these methods even in some decades for simple parts.

Example 3: A pump impeller can be milled from a material block or made by EBM. The cost Situation might change in favor of EBM sooner or later.


Last edited by HolgerNarrog on Jun 03, 2015 3:49 pm, edited 1 time in total.

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PostPosted: Jun 03, 2015 12:16 pm 
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Dear Kurt,

I can only guess about the cost comparison between 10 reactor modules of 400MWth and 1 x 4000 MWth. I assume strongly that it is significantly cheaper to have 1 big reactor.

Reasons in favor of a big reactor:

1. You only need the instrumentation, controls once in the other case 10 fold. Testing and documentation is done once in the other case 10-fold. I assume that there are a lot of components that you will need 10 fold at the same costs each.
2. The manufacturing of bigger parts does only needs a fraction of additional efforts. ex. milling a piece to 300mm instead of 200mm needs only under proportional more time (loading, adjustment & unloading)
3. Turbines, generators and other commercially available equipment does not grow proportional in costs.

Reasons against a big reactor:

1. Larger numbers of pieces are achieved
2. Mold&Tool costs are lower for smaller reactors, molds are more often used
3. Smaller components need smaller machines that are more available

It is less expensive to have 1 x 1000 hp Diesel than to have 10 x 100hp Diesel.

Example: A valve block costs 25000 CHF for fossile power plants, 60.000 CHF for a nuclear power plant over here in Switzerland. The difference is the certification, testing and documentation. The dimensions are not the cost driver. If you make 10 small ones it will cost about 6 times the costs of 1 big one.


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PostPosted: Jun 04, 2015 10:30 am 
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alexterrell wrote:
Thanks Holger,
...
The PHX is a major source of low level waste, so if this can be lightened that is a major positive.
Why don't we just recycle it. I'm pretty sure a bit of FPs mixed in with the alloy won't hurt too much. Surely they can be adjusted for.

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PostPosted: Jun 04, 2015 11:50 am 
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Dear Kiteman,

in the MCFR (my rough design) there are 5 hx of 25tons each. The costs of molybdenum material (oxide) is actually 18$/Kg. That means the base material cost of the 5 hx is about 2 Million $.

The target costs for new hx of the MCFR should not exceed 350 Mio. $. The raw material is <1% of the costs. The main costs are machining, testing, certification and documentation. By using a radioactive* base material manufacturing & testing would become more difficult and expensive. Plenty of potential manufacturer would not appreciate to work in a radioactive environment with all its headaches from protecting workers to waste management.
The molybdenum alloy TZC is difficult to manufacture and it requires a very high pureness to provide the required properties during manufacturing and during use as corrosion resistance vs. salt and as well LBE at > 800°C. I do not see any good reason to risk it.

I would suggest to put the used MCFR components pumps, hx, reactor vessels in an intermediate disposal for 100 years to reduce the radioactivity. Then you can melt it. You will gain precious non radioactive Ruthenium, rhodium and still radioactive palladium some silver and plenty of molybdenum...


Some Information:

In the MCFR 450 Kg of noble metal fp are created/yr. It should be necessary to get 95% out of the primary circuit to avoid an overheating and melting of the hx during downtimes. That means there are 675 Kg of noble metal fp in the Primary circuit. As the hx have the largest surface there are about 350 Kg of noble metal fp in the hx. The share in the hx is 0,3%.

*Mo is naturally a little bit radioactive 100Mo, 9,63 %, halftime 7,3 · 10e18 a


Last edited by HolgerNarrog on Jun 04, 2015 4:38 pm, edited 2 times in total.

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PostPosted: Jun 04, 2015 1:30 pm 
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HolgerNarrog wrote:
Reasons in favor of a big reactor:

1. You only need the instrumentation, controls once in the other case 10 fold. Testing and documentation is done once in the other case 10-fold. I assume that there are a lot of components that you will need 10 fold at the same costs each.

I was assuming that the regulations on this would be logical and allow for multiple reactor cores to be observed and controlled from a central station, something I've seen done in other power plants. I was unaware such a configuration was prohibited in a nuclear power plant. This is a regulatory limitation, not one prevented by technical limitations. We can change the laws.

HolgerNarrog wrote:
2. The manufacturing of bigger parts does only needs a fraction of additional efforts. ex. milling a piece to 300mm instead of 200mm needs only under proportional more time (loading, adjustment & unloading)

That is true but if one wanted a 1 meter machined piece it is quite possible that there are several places one might go to find the tools to do that. Suppose I wanted a reactor core that was ten times the size. For a piece that must be 3 meters (roughly cube or square root), or 10 meters (linear proportion) then the tool may simply not exist.

HolgerNarrog wrote:
3. Turbines, generators and other commercially available equipment does not grow proportional in costs.

I was assuming only the nuclear reactor would be mass produced as small modular reactors, the turbines and generators could be small in number and large in size if that made sense. I was thinking of a system like the CVN-65, eight nuclear boilers to drive four shafts, all interconnected so that the steam from all reactors are combined to drive all turbines. I envision a nuclear power plant much like that, eight or ten identical mass produced reactor cores used to drive one, two, or three, turbines.

HolgerNarrog wrote:
Reasons against a big reactor:

1. Larger numbers of pieces are achieved

Yes, economies of scale would apply.

HolgerNarrog wrote:
2. Mold&Tool costs are lower for smaller reactors, molds are more often used

As I recall one issue holding up the construction of new nuclear power plants is that there is only one or two places in the world capable of producing the core containment vessel. This means no competition on price, production rates limited by the rate of the few facilities that can produce such large items, the product must be shipped in one large piece from where it is made to the desired site, all of this increasing costs.

Small reactors that can be produced on commonly available tooling, located in various places around the world, would serve to reduce costs considerably. If these additive manufacturing machines can be moved to be on site for the production of these small modular reactors then that could prove to reduce costs more.

HolgerNarrog wrote:
3. Smaller components need smaller machines that are more available


HolgerNarrog wrote:
It is less expensive to have 1 x 1000 hp Diesel than to have 10 x 100hp Diesel.


That may be true but at some point the economies of scale fall apart. I remember seeing a large diesel engine that each cylinder was effectively a separate engine. Each cylinder had it's own fuel pump, turbocharger, and clutch. If a single cylinder was not functioning as it should it could be disengaged, shutdown, and repaired, while the rest of the engine ran. At that size a single engine block would be much too large to manufacture, so instead a block is machined for each cylinder and bolted to the others. A common drive shaft connects them all through a clutch on each cylinder. Starting an engine of such size is also an issue if all cylinders must be turned over at the same time, with the capability to disengage each cylinder separately a starter motor needs to turn only one cylinder and then each successive cylinder could be engaged using the power of the running cylinder to start.

Not knowing all the details of starting up a MSR I may be in error here but I imagine this same principle could be applied to a nuclear power plant. Imagine having to cold start a MSR. To get it to run one must take the "cold" (room temperature) salt from the storage tank, melt it, and then pump it into the core. Once there the plant would have to be run for some time to get everything warm before the plant can start to produce power. With a single 1000 MW core that would mean melting ten times as much salt than if the plant had ten 100 MW cores before any power could be produced.

Once a single core of ten is running the process of getting the rest of the cores started could be done a number of ways, depending on how it's designed. One of the few power plants I've visited had multiple boilers of differing sizes, and multiple turbines of differing sizes. I could imagine a power plant that had turbines rated at, for example, 500 MW, 200 MW, and a "baby" turbine of 50 MW that is mostly left idle. Also on site I'd imagine a set of diesel and natural gas generators for peak and backup power. Such a power plant that had to do a completely cold start would fire up a diesel generator just to get the lights on. Then the large natural gas turbines would get started to get the electric heaters going to melt the salt for the first MSR. Once the first MSR is hot enough the "baby" turbine is run. After that there is enough heat and power to fire up the other nine MSRs on site, one or two at a time.

What would it take to get a single large MSR running? How much longer would it take to get it to produce power? As it is now a single nuclear power plant often has two or three, perhaps even for or more, large reactors on site. This allows redundancy much like I described but it also requires large expensive, largely one off (not mass produced), reactor cores.

Getting back to how additive manufacturing can make this happen I've seen estimates that a 20 MW or so core would be about one meter on a side, roughly. Something like that might take one month to produce by additive manufacturing but that is now a highly detailed solid piece of metal that could not have been cast with existing tools. It would also be of a size that, I assume, could be easily tested in machines used to test things like aircraft parts. The entire "boiler" (for lack of bigger vocabulary) would be small enough to fit inside a standard ISO container for shipping to the power plant. Once on site it can be connected to the gigawatt scale turbine and generator, along with ten others just like it.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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PostPosted: Jun 05, 2015 11:11 am 
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One caveat re: additive manufacturing processes for metal is that often the material properties are different when compared to casting, forging, hot rolling, et cetera.


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