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PostPosted: Feb 20, 2011 7:09 am 
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I wonder how much faster nuclear ships would go, optimally. Twice as fast means 8 times the reactor capacity which sucks. I guess this depends on the non-fuel cost percentage of a ship. If the non-fuel costs are big, it makes sense to go faster as these non-fuel costs, such as ship capital and crew, will be lower per nautical mile.

I think nuclear ships will have more space for cargo with no bunker fuel. And don't have to worry about being able to refuel in every harbor. These are nice advantages too.


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PostPosted: Feb 20, 2011 7:57 pm 
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I tried looking up some details for the Emma Maersk (Largest operating cargo ship) to get some feel for this.

Theoretical hull speed is ~50 kt (=81 km/h)
Actual top speed at full power (80Mw) = 31 kt (51 km/h), 63% of hull speed
Design cruising speed = 25 kt (=41 km/h), 50% of hull speed. I haven't found the power requirement for this speed, but assuming cubic scaling it is 42 Mw.
With high fuel prices and lower demand for shipping, running at 21 kt (25 Mw if cubic) has become common.

A similar ship with 100 Mw nuclear propulsion, run at full power, would travel at 33 kt, only marginally faster than Emma Maersk can, but ~50% faster than it does, on expensive oil.


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PostPosted: Feb 21, 2011 5:02 am 
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Here are some more rough numbers form those links the price of Emma Maersk was about USD145M

If you had a 100 MW nuclear propulsion system costing USD3,000/kW that would be USD 300M.

So how does that compare to the potential cost savings on fuel, ignoring the benefits of carrying more cargo each year?

IF380 fuel oil at ~ USD600/tonne, 0.26lb/BHPh, 70 MW, at sea 80% of the time. Annual Fuel bill = USD 47M

If the nuclear plant costs say $7/MWh to run for fuel, fuel processing and disposal, that's about $3.4M/year. Potential fuel savings of 43.5M/y, the present value of those fuel savings over 30 years = $411M i.e. 111M better off than burning HFO after paying for the higher initial capital cost.

So it look s economic, but to really be worth while the capital cost of the nuclear propulsion system would have to be quite a bit less than $3,000/kW installed. The upside for the ship owner would come when the price of HFO goes to $1200/t


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PostPosted: Feb 21, 2011 7:59 am 
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According to Wikipedia, here are some figures on the NS Savannah, the first nuclear powered freight ship:

Quote:
NS Savannah, named for SS Savannah, was the first nuclear-powered cargo-passenger ship, built in the late 1950s at a cost of $46.9 million, including a $28.3 million nuclear reactor and fuel core, funded by United States government agencies as a demonstration project for the potential usage of nuclear energy.[3] Launched on 21 July 1959, she was in service between 1962–1972.[2] NS Savannah is one of only four nuclear-powered cargo ships ever built, while Soviet ice-breaker Lenin launched on 5 December 1957, was the first nuclear-powered civil ship.


http://en.wikipedia.org/wiki/NS_Savannah

Tripling these costs to take into account inflation, makes 141 million for the ship of which 85 million for the reactor. Though it would appear the ship was too small in freight capacity. It would have to be over 6 times bigger in net freight tonnage to match the Emma Maersk. The article mentioned that the smaller size was deliberate as it is a demonstration project. I wonder if a large scale model could be built for under half a billion like Lindsay says. It seems tough especially with today's absurd bureaucracies on nuclear power plants. Though the small modular reactors like NuScale suggest the cost per kWe is not bigger than large reactors.


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PostPosted: Feb 21, 2011 11:53 am 
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China and South Korea are the biggest shipbuilders and upcoming nuclear builders. They also have lowest nuclear building costs. Once they decide to build smaller reactors, the ships could be economically provided with nuclear power.


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PostPosted: Feb 21, 2011 2:11 pm 
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Lindsay wrote:
Here are some more rough numbers form those links the price of Emma Maersk was about USD145M

If you had a 100 MW nuclear propulsion system costing USD3,000/kW that would be USD 300M.

So how does that compare to the potential cost savings on fuel, ignoring the benefits of carrying more cargo each year?

IF380 fuel oil at ~ USD600/tonne, 0.26lb/BHPh, 70 MW, at sea 80% of the time. Annual Fuel bill = USD 47M

If the nuclear plant costs say $7/MWh to run for fuel, fuel processing and disposal, that's about $3.4M/year. Potential fuel savings of 43.5M/y, the present value of those fuel savings over 30 years = $411M i.e. 111M better off than burning HFO after paying for the higher initial capital cost.

So it look s economic, but to really be worth while the capital cost of the nuclear propulsion system would have to be quite a bit less than $3,000/kW installed. The upside for the ship owner would come when the price of HFO goes to $1200/t


Assuming that the diesel engine costs $50,000,000 that means that it is a $250,000,000 increase in base capital cost to build the nuclear ship vs. the diesel.

Using your assumed $43,500,000 variable cost savings per year we get the following out to 30 years if we assume a reasonable 9% cost of capital and 36% tax rate:

IRR = 13.5% (currently no where near what my business demands for investment, which is typically > 40% and often closer to 100%)
NPV = $96,100,000

The project is not cash flow positive until year 9, which is way beyond a more typical 3-5 I see for investment (granted most of what I see is more in the $50k-2M sized projects).

Bottom line is that the payback with the above assumptions is only marginal.


However, if the cost of the reactor drops in half (mass production) and the cost of oil doubles, then the results shift to the following:

IRR = 61%
NPV = $621,000,000

The project is now cash flow positive in year 2.

In this case, it would be insane to use diesel.


These simple analysis do not cover the increased revenue/profit from running faster and thus moving more cargo. I would expect that these would be significant contributors to the project valuation; however, I do not know if the sensitivity would make the first case attractive enough or not.


Last edited by cld12pk2go on Feb 21, 2011 3:41 pm, edited 3 times in total.

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PostPosted: Feb 21, 2011 2:51 pm 
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Interesting. Today's small modular reactors in development are expecting cost targets of 4000 USD/kWe (NuScale) to 5000 USD/kWe (mPower). Too high. Look to Asian countries to take up leadership on cheaper small modular reactors where the US has, again, dug its own grave.

Now a more reasonable hope than the US taking leadership in nuclear power technology is for 200 dollar a barrel oil to happen and stay there...


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PostPosted: Apr 07, 2011 1:30 am 
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To offer some comment from the other side of this field (Naval Architecture, ie ship design), 100MW is in general too big for the vast majority of shipping needs. Even the very largest of ships will struggle to make efficient use of that amount of power.

Realistically, what would be ideal for the larger sizes of vessel is a 25MW modular unit. At that scale, you would have interest from large cargo vessels, high speed transport vessels, military craft and possibly cruise ships.

Smaller than that, a 4-6MW unit would be superb. I could see uses down to 150kW or so for fishing vessels, if it can be done in a reasonable size and weight.

I can't make comment on how practical or impractical that is from the nuclear design side, but if you are asking what I would want as a Naval Architect who has an interest in being able to fit a modular reactor to a vessel, those would be my target sizes.

Priorities other than that are weight and volume. This is not a civil engineering task piece. Weight and volume are critical to their being a real justification for using these. Fuel cost is there, but not nearly as critical for many applications as one might think. Otherwise you would never see a gas turbine on board a ship.

100MW I would have no interest in whatsoever.

If you have specific questions regarding boats, feel free to ask.


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PostPosted: Apr 07, 2011 6:59 am 
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Forge wrote:
To offer some comment from the other side of this field (Naval Architecture, ie ship design), 100MW is in general too big for the vast majority of shipping needs. Even the very largest of ships will struggle to make efficient use of that amount of power.

Realistically, what would be ideal for the larger sizes of vessel is a 25MW modular unit. At that scale, you would have interest from large cargo vessels, high speed transport vessels, military craft and possibly cruise ships.


I'm not sure I believe you:

http://en.wikipedia.org/wiki/A4W_reactor

The Nimitz super carriers have two of these, producing some 200MW.

http://en.wikipedia.org/wiki/D2G_reactor

"Rated for a maximum thermal output of 150 megawatts" and two of them are used on cruisers. Granted that's thermal output so electric or shaft horsepower would only translate to maybe 50MW. A total power output of 100MW for a cruiser that uses two of them.

I doubt you can go much lower than 50MWe efficiently. I'm not sure you can even go that low on fuel enriched to 20% or less. The smaller you go the higher the enrichment you're going to require as far as I know, and your cost savings of reducing reactor output are in the realm of diminishing returns while your political obstacles of using highly enriched fuel go up. I'm guessing 100MWe output is close to the ideal size, and if that extra 75MW power is dumped into raising the ship speed by 10% compared to saving 5% making the reactor only 25MW thats nearly the same size and same cost...

Its all too soon to tell now. The question might be more along the lines of if its cheaper than a fossil fuel cycle over its lifetime, and you have a smallest size of 100MW, how would you use it? Because you might not get anything smaller than that.


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PostPosted: Apr 07, 2011 7:42 am 
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You can believe what you like. The market at 100MW is there, but limited to naval craft and the very largest of containerships. Do realize that the carrier you mentioned is nearly 400m long and goes at 45knots - there really is nothing else of that scale and speed made.

The largest diesels are only just clear of 100MW.

If you want to provide a significant number of installations, you've got to look smaller. It's easy enough to install 4 x 25MW to get 100 if it's needed. You can't divvy up a big one for a smaller installation. I'm not certain of the numbers, but it wouldn't surprise me at all if you could find 100 ships at 25MW+ for every 1 at 100MW+.


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PostPosted: Apr 07, 2011 9:27 am 
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With diminishing returns from higher power, it may be time for fresh thinking. The ships can be designed as convertible to hovercraft in open sea and good weather. In such favorable conditions, they could run faster with reduced water resistance. Slower speeds and better control is required in and near ports and in bad weather.
The second possibility is nuclear tugs. In addition to port duties, they could be used as locomotives cum power units for sea going rafts. Spare units can be sent if and when required. The rafts could be designed as hydroplanes for reduced drag at high speeds.
Nuclear power must be used as part of overall engineering. After all, it started as prime mover for submarines.


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PostPosted: Apr 07, 2011 9:30 am 
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Forge wrote:
You can believe what you like. The market at 100MW is there, but limited to naval craft and the very largest of containerships. Do realize that the carrier you mentioned is nearly 400m long and goes at 45knots - there really is nothing else of that scale and speed made.

The largest diesels are only just clear of 100MW.


Sure. I don't suspect that nuclear powered shipping will be desirable for anything smaller. The only ships that it makes sense for now are the largest ships in the fleet. I read your initial comments as there were no markets for large power plants in shipping, rather than a very small market.

Quote:
If you want to provide a significant number of installations, you've got to look smaller. It's easy enough to install 4 x 25MW to get 100 if it's needed. You can't divvy up a big one for a smaller installation. I'm not certain of the numbers, but it wouldn't surprise me at all if you could find 100 ships at 25MW+ for every 1 at 100MW+.

What I'm saying is 100MW might be the smallest reactor you can get for a civilian design that is cost effective... maybe 50MW. If we move towards nuclear powered shipping we'll likely just see a trend towards larger ships to manage the overhead of a nuclear power plant.

http://www.world-nuclear.org/info/inf33.html

There are some power reactors that produce under 50MW, so this could change, but I'm suspicious of the economics of the capital and operations costs of power plants smaller than 50MW, which is why I'd be more interested in the largest ship operations. I'm under the impression that nuclear powered shipping would make the most sense in large ships before attempting to negotiate the capital and operations cost of replacing the power plants of ships under 50MW.


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PostPosted: Apr 07, 2011 9:53 am 
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I picked Maersk class as the comparison because they are so big (and the information is available). If nuclear isn't competitive at that scale, it's not going to work at all, but there are very few such ships. The Koreans are thinking of building something a bit bigger still, but slower and less powerful. Small reactors are possible - at the scale Forge is talking about, the obvious choice is Hyperion, at 25Mw/module The Russians have used related reactors for icebreakers and subs, so it is technically possible. Economically - maybe wait for $200 oil, and Chinese reactor construction costs.

A salt-cooled design might work. Per's AHTR is focussed on capital cost reduction, not fancy reprocessing systems for minimum waste and resource consumption, and TRISO fuel is almost disposal-ready as-is. You have to assume a reactor is going to sink at some point, so not leaking anything nasty, even if you don't find it for years, is important. Anyone know if an AHTR-type reactor could be made over-moderated, so seawater ingress doesn't increase reactivity?


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PostPosted: Apr 07, 2011 11:10 am 
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Salt water is a neutron poison isn't it? Pure light water captures 9 times as many neutrons per unit volume as FLiBe and over 70 times as much as graphite. That's without all that chlorine, sodium, potassium, sulphur, magnesium, dirt etc. in seawater.


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PostPosted: Apr 07, 2011 5:09 pm 
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Just to clarify, I'm talking about 25MWe, not 25MWt.

And you may well be right that the initial economies work out better for larger vessels. I've never been entirely sure if nuclear worked out the size it did because of purpose (I.e base load power) or whether it was that way because it only worked well at that scale.

I'll just reiterate that the priorities for a marine plant are different. Efficiency is nice, but the efficiency of the boat as a whole is where it is measured. Every bit of weight means the boat requires more power to operate, every bit of space means less volume available for cargo.


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