Small Modular Naval Reactors

[Vanadium 50]

Will SMR's (Small Modular Reactors) allow for nuclear powered surface combatants to make a comeback?

The US Navy used to operate a fleet of nuclear powered cruisers in addition to aircraft carriers and submarines. Most were based on the General Electric D2G reactor, which is around 30x30x40 (height) feet in size and delivered 50 MW or so.

These were all decommissioned in the 90's for a number of reasons:

1. Refueling was length and expensive - the reactors were so large you needed to cut a big hole in the ship to get where you needed to go.
2. The crew that operated these reactors needed to be highly trained. Costs are comparable to training a pilot. You also needed trained crew to handle activities that were important but not directly part of running the reactor, like reactor chemistry.
3. The power quantization is coarse - if you need 1.1 reactors, you need to have 2. That makes them expensive.
4. Gas turbine technology replaced steam; this takes fewer people to operate, in no small part because if something breaks, you can't easily fix it - so reliability must go up.

SMRs address at least three of these.

1. They are smaller and easier to replace
2. They require very little in the way of operators - in many ways they are more like a battery than a reactor.
3. Granularity is finer, although the eVinci's 5 MW probably takes it too far.

I'm surprised the US Navy isn't salivating over this. Granted, neither Westinghouse nor NuScale amkes exactly what is needed, but both come close.

Reactor + fuel cost is comparable to conventional fuel cost, per year of operations. But, you don;t have to worry about supply lines to get your fuel to your ship. Every few years you refuel -- at home.

Is there some reason they haven't jumped on this?

 

[hutchphd]

What enrichment level is required for the fuel?

 

[Vanadium 50]

I don't know, but given that the first eVinci is being exported, it can't be too dangerous with respect to proliferation - I presume this is your concern. Personally, having it guarded by large men with very large guns seems like a good idea.

 

[nsaspook]

I installed non-tactical computer systems on most of the old nuclear powered surface combatants in the 80's during their yard periods so I've seen how expensive repairs on that class can be. They were Cold War era weapons that had tactical nukes for Soviet naval targets when you expected to have most friendly ports also nuked by the Soviets so they needed the reactors for the WW3 death run.

Nuclear-powered guided-missile cruisers USS California, USS South Carolina, USS Virginia, USS Texas, USS Mississippi, and USS Arkansas in February 1981

The practical, at sea duration for the ship is fairly short due to limited storage for food and supplies unless you have a a string of supply ships that will have fuel for the non-nuclear fleet or access to a local port that will also have fuel.

The basic reason they haven't jumped on this is it gives a capability that's not really needed in today's expected combat action types.

 

[Vanadium 50]

The basic reason they haven't jumped on this is it gives a capability that's not really needed in today's expected combat action types.

That may be their thinking, but I am not sure it is correct.

At $75-80 per barrel, operating costs may not be competitive. At $150-160 you better believe nuclear is a better option.

The US has replaced 13 Ticos, 31 Spruances, 10 DDGs of various classes, 9 cruisers and 51 Perrys with 71 Burkes. If you have 30% fewer ships, you need them to spend 30% more time at sea or you lose capability.

You could also being back smaller combatants. The LCS fiasco ("Daddy, are the LCSs the worst designed ships in the world?" "Well, son, there was the Vasa, but yes..yes they are." ) did leave a bad taste in everybody's mouth, that doesn't mean the concept is wrong. Lots of nations have corvettes.

 

[nsaspook]

That may be their thinking, but I am not sure it is correct.

At $75-80 per barrel, operating costs may not be competitive. At $150-160 you better believe nuclear is a better option.

The US has replaced 13 Ticos, 31 Spruances, 10 DDGs of various classes, 9 cruisers and 51 Perrys with 71 Burkes. If you have 30% fewer ships, you need them to spend 30% more time at sea or you lose capability.

You could also being back smaller combatants. The LCS fiasco ("Daddy, are the LCSs the worst designed ships in the world?" "Well, son, there was the Vasa, buty yes..yes they are." ) did leave a bad taste in everybody's mouth, that doesn't mean the concept is wrong. Lots of nations have corvettes.

Those missiles we are using to kill drones cost ~million each using the cheap ones.

https://responsiblestatecraft.org/operation-prosperity-guardian/

According to experts, the US Carney and US Mason destroyers (also joined by U.K. warships in some cases) could be using a mix of RIM66 SM-2 and RIM66 SM-6 interceptors as well as ESSM Sea Sparrows to take down the drones. The Carney is outfitted with SM-3s as well, but it is not clear that they are being used. This is all part of a “layered defense” that deploys different interceptors depending on the threat. The missiles mentioned so far in numerous interception reports have been the SM-2 and the Sparrows.

According to the Missile Defense Advocacy Alliance (as of 2022), the SM-2 costs $2.1 million per unit; the SM-6 costs $4.3 million; and the ESSM Sea Sparrows costs $1.7 million. The destroyers are also fitted with the Rolling Airframe missile, which cost $905,000 in 2022. One source suggested, however, not to assume the high end of the cost, adding that the U.S. Navy was likely cleaning out their old stocks and not using the latest versions of these interceptors.

You can buy a lot of DFM with that.

The Ticos and Spruances (I installed ADP systems on them too) were good ships (big ships, with big crews) but they were designed to fight a war, that thank goodness, never happened. With the right mix of capabilities, the absolute number of ships is less important than the ability to get the job done efficiently with the fewest people.

I've hired several former Navy nuclear ET guys. They've got one job on the ship, at the reactor and they know how to keep it running when the chips are down.

Your typical snipe on an oil burner/GE turbine can handle several other duties.

The Navy is short of people, not ships.

 

[Vanadium 50]

First drones are an issue. So were torpedoes a century ago. Weapons will continue to evolve. But ships will still need propulsion.

If the LCS fiasco told us anything (and arguably it didn't) it's that you cannot substitute speed for hulls. The idea was while you couldn't be in two places at once, with a fast enough ship, you could almost be in two places at once. The designers lost sight of the fact that a warship stuck in port because of engineering casualties or inordinate time swapping "mission modules" it is essentially a very expensive building, nothing more. The designers felt speed is everything and at the end of the day, that's all they had.

The advantage of gas turbines is, as you allude to, the fact that they need fewer crew members to operate. Heck, a 747 has four of them and it needs only a pilot and co-pilor, both of whom have other duties, like making sure the pointy end of the plane is in the right direction and the bottom of the plane doesn't scrape the ground. But this is only the start - since there is so little that can be repaired in place, you don't need a repair team. And that means you don't need as many cooks. And so on and so on. SMRs have the potential to continue this trend: the concept is that they are more like a battery than a steam plant.

I would also argue there is no substitute for hulls. An important capability that is being lost is the role of Protection Of Shipping. We saw it with Somali pirates and we see it with Houthi insurgents - you can't be everywhere at once, and you don't need a ship that can take on the Sovi...er...Russ....er....Major Adversarial Powers. But you do want one at sea, and you do want one that can stay at sea without worrying about running out of gas.

 

[Astronuc]

Will SMR's (Small Modular Reactors) allow for nuclear powered surface combatants to make a comeback?

Perhaps refer to marine reactors. Russia has nuclear powered ice-breakers.

Certainly, the right-sized nuclear plant is feasible. However, what technology - LWR, MSR, SFR, PbBi-FR?

China has announced plans for a nuclear powered container ship.
https://www.msn.com/en-us/news/worl...nese-innovation-or-global-concern/ar-AA1mf9gt

https://en.wikipedia.org/wiki/Nuclear_marine_propulsion

 

[nsaspook]

First drones are an issue. So were torpedoes a century ago. Weapons will continue to evolve. But ships will still need propulsion.

If the LCS fiasco told us anything (and arguably it didn't) it's that you cannot substitute speed for hulls. The idea was while you couldn't be in two places at once, with a fast enough ship, you could almost be in two places at once. The designers lost sight of the fact that a warship stuck in port because of engineering casualties or inordinate time swapping "mission modules" it is essentially a very expensive building, nothing more. The designers felt speed is everything and at the end of the day, that's all they had.

The advantage of gas turbines is, as you allude to, the fact that they need fewer crew members to operate. Heck, a 747 has four of them and it needs only a pilot and co-pilor, both of whom have other duties, like making sure the pointy end of the plane is in the right direction and the bottom of the plane doesn't scrape the ground. But this is only the start - since there is so little that can be repaired in place, you don't need a repair team. And that means you don't need as many cooks. And so on and so on. SMRs have the potential to continue this trend: the concept is that they are more like a battery than a steam plant.

I would also argue there is no substitute for hulls. An important capability that is being lost is the role of Protection Of Shipping. We saw it with Somali pirates and we see it with Houthi insurgents - you can't be everywhere at once, and you don't need a ship that can take on the Sovi...er...Russ....er....Major Adversarial Powers. But you do want one at sea, and you do want one that can stay at sea without worrying about running out of gas.

I agree but running out of gas is the least of their worries in that part of the world. That region is a gas can for shipping fuel.

There is a long tradition of knowing your engine down to the last bolt in the Navy.


The SMR might be 'better' but there's a lot of infrastructure for DFM, for a swatch of ship types, with contracts (money) for fueling around the world that gives an incentive for port access in places that don't really like the USA but are glad to take our money.

 

[Vanadium 50]

that gives an incentive for port access in places that don't really like the USA but are glad to take our money.

Fat Leonard, anyone?

The problem I have with this argument is that it also can be applied to aircraft carriers. If you think destroyers use a lot of fuel, take a look at the JFK. That ship (alone, not the embarked air wing) ~12x the power of a Burke. (There is a famous picture of the Kennedy leading a fleet of ships - and on closer inspection, the ships are all oilers)

Perhaps refer to marine reactors. Russia has nuclear powered ice-breakers.

Yes they do. They need them. There have also been a handful of merchant ships, like the Savannah and the Otto Hahn. The problem is that most civilian ships simply don't need that much power. If a ship isn't fast enough, send it by air.

Also, if a container ship is in port, it's loading and unloading freight - i.e. still doing its job. If a warship is in port, that's a different story. There is significant incentive to keep them on the high seas. (Ballistic missile submarines are limited by crew endurance - so they have two sets of crews)

However, what technology - LWR, MSR, SFR, PbBi-FR?

What do you think?

 

[Rive]

Perhaps refer to marine reactors. Russia has nuclear powered ice-breakers.

BTW, is it something new to re-brand these marine reactors as small-modular?
Just run across this trend some weeks ago: or, at least I can't recall KLT40S mentioned as SMR until recently.

 

[gleem]

What enrichment level is required for the fuel?

19.75% TRi-structural ISOtropic pelletized fuel (TRISO)

Each TRISO particle is made up of a uranium, carbon and oxygen fuel kernel. The kernel is encapsulated by three layers of carbon- and ceramic-based materials that prevent the release of radioactive fission products.

see https://www.usnc.com/triso/ for more details

 

[Astronuc]

BTW, is it something new to re-brand these marine reactors as small-modular?
Just run across this trend some weeks ago: or, at least I can't recall KLT40S mentioned as SMR until recently.

Yes, it is a recent trend to emphasize small reactors are modular, but it does indicate a difference in which the small reactor is contained in a smaller pressure vessel, ostensibly more portable, than prior small reactors in which the reactor (pressure) vessel was integrated into the primary cooling system. Saxton (PWR) and Big Rock Point (BWR) were small reactors.

The US military has tried small ('portable') reactors in the past, e.g., PM-2A.

The PM-2A nuclear reactor at Camp Century, Greenland, was a temporary facility. After three years the Army shut it down, dismantled it, and removed it from the station.

https://www.atlasobscura.com/articles/camp-century-portable-nuclear-reactor
Original article - https://theconversation.com/the-us-...te-bases-60-years-ago-it-didnt-go-well-164138

The Army called the reactor portable, even at 330 tons, because it was built from pieces that each fit in a C-130 cargo plane. It was powering Camp Century, one of the military’s most unusual bases.

Camp Century was a series of tunnels built into the Greenland ice sheet and used for both military research and scientific projects. The military boasted that the nuclear reactor there, known as the PM-2A, needed just 44 pounds of uranium to replace a million or more gallons of diesel fuel. Heat from the reactor ran lights and equipment and allowed the 200 or so men at the camp as many hot showers as they wanted in that brutally cold environment.

The PM-2A was the third child in a family of eight Army reactors, several of them experiments in portable nuclear power.

A few were misfits. PM-3A, nicknamed Nukey Poo, was installed at the Navy base at Antarctica’s McMurdo Sound. It made a nuclear mess in the Antarctic, with 438 malfunctions in 10 years including a cracked and leaking containment vessel. SL-1, a stationary low-power nuclear reactor in Idaho, blew up during refueling, killing three men. SM-1 still sits 12 miles from the White House at Fort Belvoir, Virginia. It cost US$2 million to build and is expected to cost $68 million to clean up. The only truly mobile reactor, the ML-1, never really worked.

SL-1 was like Chernobyl. Someone (who manually removed a control rod from the core) took the reactor outside its design envelope and initiated a reactivity insertion accident (RIA). RIA is where positive reactivity is inserted into a core, which then causes a surge in neutrons/fission. If the power denisty is too high, i.e., the fuel temperature exceeds a predetermined threshold, then fission gases (Xe, Kr) and volatiles fission products (e.g., Te, I, Cs, Br, Sr) may cause the fuel to expand and rupture, or in extreme cases, explode.

In May 2021, the Pentagon requested $60 million for Project Pele. Its goal: Design and build, within five years, a small, truck-mounted portable nuclear reactor that could be flown to remote locations and war zones. It would be able to be powered up and down for transport within a few days.

The Conversation article mentions the success of the Navy program, and also refers to the loss of the and Thresher (Apr 1963) and Scorpion (May 1968) nuclear powered submarines.

 

[Vanadium 50]

BTW, is it something new to re-brand these marine reactors as small-modular?

I think there is an undercurrent of simpler operation, not just small size. eVinci markets itself as a "nuclear battery" implying it does not need a team of experts to operate it. Obviously this is on a continuum.

 

[Rive]

I think there is an undercurrent

I found this sudden re-branding (of existing naval reactors) almost exclusively related as a proof of Russia being the world leader in SMR technology.
I could not help to suspect a very different type of undercurrent there...

 

[Vanadium 50]

I would say existing naval reactors are small, but not so modular. The A2W might be "modular" in that the ship driven by them carried 8.

 

[Astronuc]

KLT40S

No, it is a more traditional PWR.
https://aris.iaea.org/PDF/KLT-40S.pdf

Portable reactors have to be 'compact' as compared to other larger reactors. The core has to be a certain size in the form of a right circular cylinder to accommodate heat removal as well as minimizing neutron leakage. The control elements are usually on top of the core so they can drop under gravity in a matter of seconds (usually less than 2 s), otherwise (as in the case of BWRs), they are inserted hydraulically from below. Some reactor designs may have control drums on the side of the core, which control the reflected neutrons, but there are usually shutdown control rods inserted from either end (or top or bottom).

Compact designs put the primary heat exchanger(s) as close to the core as possible, subject to limits on the neutron flux (to minimize activation). The primary heat exchangers produce steam in a separate coolant circuit.

To minimize neutron leakage from the core, the core may be surrounded by a 'blanket' of lower enriched fuel, or something inert like Fe or C, in some form. In addition, the fuel elements are design with blankets (lower enrichment, or natural U based fuel, or perhaps even a metal carbide), at each end (or top and bottom) of the fuel stack.

 

[Astronuc]

I think there is an undercurrent of simpler operation, not just small size. eVinci markets itself as a "nuclear battery" implying it does not need a team of experts to operate it. Obviously this is on a continuum.

Yes, the smaller reactor is perhaps more self-regulating. eVinci is quite different from older more conventional designs, and it is considered a microreactor.

https://www.westinghousenuclear.com/energy-systems/evinci-microreactor

 

[Astronuc]

19.75% TRi-structural ISOtropic pelletized fuel (TRISO)see https://www.usnc.com/triso/ for more details

Probably something like HALEU. Enrichment depends on power density, cycle length or core life time, and how frequently one would plan to refuel. Enrichment is as low as reasonable achievable subject to design requirements and engineering constraints.

As V50 indicated, refueling can be a challenge, depending on how the hull and structure are designed and fabricated. Ideally, the ship is watertight in the most adverse conditions.

 

[nsaspook]

Related story.
https://gcaptain.com/uss-carney-returns-to-persian-gulf-with-combat-honors/

USS Carney Returns To Persian Gulf With Combat Honors​

The Navy has not stated if the USS Carney will return to the Red Sea. It will likely take some time for the ship to replenish stores and reload VLS anti-air missiles expended in combat.

IMO engines are not the limiting factor for on station time for these types of ships. People and weapons are.

Fat Leonard, anyone?

The problem I have with this argument is that it also can be applied to aircraft carriers. If you think destroyers use a lot of fuel, take a look at the JFK. That ship (alone, not the embarked air wing) ~12x the power of a Burke. (There is a famous picture of the Kennedy leading a fleet of ships - and on closer inspection, the ships are all oilers)

Fat Leonard was one of many. The current facilitator is a little more careful with the types of parties and gifts they give.

Going nuclear (that are refueled only a few times in a carrier lifetime) on a carrier was an easy choice because of very limited port call and servicing availability while deployed.

I've got old (bad) pictures of us landing a CH-53 on the USS Nimitz (nuke) in 1980 while on route to the USS Coral Sea (oil) to repair some electronics equipment. We all did ~100 continuous days at sea at GONZO station.

She's scheduled for deactivation in 2027 per the latest news.

 

[Vanadium 50]

The argument about manpower and munitions is essentially "we have bigger fish to fry". That may well be true, but the Navy still needs to move their ships. This seems like a better way to do it - possibly with lower manpower needs. (Although GTs are pretty low, precisely because you can't easily fix anything at sea)

As far as "buying oil makes our friends happy" as national policy, such a policy has risks. The recent attacks on the Carey were supported by an oil-exporting state. You don't want to depend on such a a resource.

Just to set the scale. I believe there are 12 aircraft carriers, 2 battlecruisers and 4 icebreakers in service, operated by 3 of the world's navies.

 

[Vanadium 50]

One thing I don't understand, and maybe this impacts the question I asked @Astronuc has to do with xenon. If I shut off a reactor, say overnight, and try and turn it on with the same settings, it won't go - the xenon produced in the fission daughters decays eats neutrons. I either have to wait a few days for it to decay, or adjust the settings to compensate. I am not sure what a "push-button" reactor does to solve this.

 

[nsaspook]

(Although GTs are pretty low, precisely because you can't easily fix anything at sea)

You can fix a lot on a GT at sea.

As far as "buying oil makes our friends happy" as national policy, such a policy has risks. The recent attacks on the Carey were supported by an oil-exporting state. You don't want to depend on such a a resource.

True that, that's why a facilitator like Fat Leonard is always going to be needed. All they care about is the money.

We were in bed with this crook because he was more dependable than our own suppliers and private defense contractors when we needed supplies to keep the fleet on station in some far flung part of the world.

Realistically, I just don't see much momentum around the SMR concept from the former Navy reactor engineers and techs at work, none of guys I know want to be a 'Copper Top' battery watcher.

 

[Vanadium 50]

I just don't see much momentum around the SMR concep

Sure, but there's never enthusiasm when the alternative is "we've always done it this way".

Steam turbines.
Gas turbines.
Retirement of battleships.
Retirement of cruisers. (The last true cruiser was laid down 65 years ago!)
Combination of fighter and attack aircraft
Replacement of guns with missiles
And, of course, Nuclear propulsion to begin with.

I think a strong case can be made for surface combatants, but there is also a case to be made for LHA/LHD's. A Wasp weighs the same as the Charles deGaulle, which is nuclear powered. The US Navy doesn't call them aircraft carriers. Just ships that carry aircraft.

 

[gmax137]

One thing I don't understand, and maybe this impacts the question I asked @Astronuc has to do with xenon. If I shut off a reactor, say overnight, and try and turn it on with the same settings, it won't go - the xenon produced in the fission daughters decays eats neutrons. I either have to wait a few days for it to decay, or adjust the settings to compensate. I am not sure what a "push-button" reactor does to solve this.

Naval reactors can't be allowed to let the xenon win. They are designed with a lot more excess reactivity than power reactors.

 

[gmax137]

I found this, which might be of interest.

https://www.jstor.org/stable/resrep14271.9

... These differences between naval reactors and civilian power reactors are often not understood even by nuclear engineers who have not been exposed to naval propulsion reactors. For example, all reactors produce xenon isotopes in normal operation. Once a reactor is shut down either intentionally or via an unintentional SCRAM (emergency shutdown), a radioactive xenon poison builds up, which can prevent civilian power and research reactors from going critical until the poison (which is itself radioactive) has decayed away. Naval reactors can never be put in the position of being unable to override xenon build up, a fact that requires naval reactor cores (whether they use LEU or HEU) to contain more excess reactivity than other types of reactors and therefore they require refueling earlier in their lifecycle then would be done if their cores were operated in a civilian power production mode and could be allowed to burn longer...

 

[Vanadium 50]

One of the nice things about GT's is that you push a button and they are ready to go. Steam takes a day or two to go from cold iron to full power. (Possibly longer for the JFK or an Iowa battleship) That comparable to xenon lifetime.

This is, however, where modularity is a bonus. If you have one reactor, it absolutely has to work all the time. Otherwise you're sunk. No pun intended. Mostly. If you have four, and three are operating, and the fourth comes on the day after tomorrow, it is perhaps less of a crisis.

 

[nsaspook]

Sure, but there's never enthusiasm when the alternative is .

Steam turbines.
Gas turbines.
Retirement of battleships.
Retirement of cruisers. (The last true cruiser was laid down 65 years ago!)
Combination of fighter and attack aircraft
Replacement of guns with missiles
And, of course, Nuclear propulsion to begin with.

I think a strong case can be made for surface combatants, but there is also a case to be made for LHA/LHD's. A Wasp weighs the same as the Charles deGaulle, which is nuclear powered. The US Navy doesn't call them aircraft carriers. Just ships that carry aircraft.

Most of the time that "we've always done it this way" tradition makes you really prove something is better aka your reference to the LCS fiasco.



I was on a old LPH class ship for 2+ years with a crew of 600 sailors and 2000 marines. The LHA/LHD/LPH carry aircraft but their mission is distant from what a typical aircraft carrier would be. Close in ground support of infantry was their job on my old ship and I'm pretty sure not much has changed.

This is us in 1980 at port in Singapore months before the Iran mission in the gulf.

We had old school oil fired steam engines.

Maybe an SMR is a good idea for this class of ship.

 

[Vanadium 50]

I won't be hating on the LCS. Other people do it better. I think, however, one of the many lessons we learned is that speed does not compensate for hulls. The idea was that a 45 knot vessel was as good as 1.5 30 knot vessels. That sounded fishy from the get-go. And it was.

Unlike the LCS, there is a clear rationale for nuclear power: reduce reliance on petroleum deliveries in the theater of operations. Depending on reactor design, it might take fewer people to operate, and it might be slightly cheaper, but I wouldn't count on this. After the Pentagon gets through with it, it may well cost more.

I'm also not advocating a reactor on every rowboat. More or less in order:

1. Submarines (already done)
2. Aircraft carriers (already done)
3. Destroyer/cruiser-type vessels to screen carriers (started and then reversed)
4. LHA/LHD type amphibious ships (essentially, smaller carriers)
5. Destroyer/cruiser-type vessels to screen LHAs
6. AOE-type supply ships - wouldn't you want to be able to traverse an ocean twice as fast?
7. Destroyer/cruiser-type vessels to screen AOE's.

There seems to be a common theme, and it seems reasonably well-matched to what SMRs can do.

 

[Astronuc]

Unlike the LCS, there is a clear rationale for nuclear power: reduce reliance on petroleum deliveries in the theater of operations.

That is the thinking behind portable reactors - perhaps portable microreactors. The question then is how portable, e.g., is eVinci sufficiently portable - over rough terrain?

Marine SMRs may be more practical/realistic - but what would that look like? What kind of power plant?

Looking at the Arleigh Burke class propulsion plant -

Propulsion

4 × General Electric LM2500 gas turbines each generating 26,250 bhp (19,570 kW);[6] coupled to two shafts, each driving a five-bladed reversible controllable-pitch propeller; Total output: 105,000 bhp (78,000 kW

https://en.wikipedia.org/wiki/Arleigh_Burke-class_destroyer

Plus another system for house power - ~10 MW?

 

[Flyboy]

Even on the civilian front, the reactor does make a lot of sense, at least for the big container freighters. They burn a lot of fuel oil per trip, and the cost of that over time is only going to go up. If you switch to nuclear, yeah, it's higher upfront costs, and refueling is expensive when it does happen, but you don't have to buy fuel for every leg of your journey, detours around geopolitical hotspots doesn't cost anything more than the lost time, you significantly reduce your emissions footprint, and if deployed properly and safely, it's a huge proof of the fact that modern nuclear power is indeed safe for widescale use and decarbonization of major emitters like the shipping industry. It'd be less about the speed, although you probably could go faster than a maritime diesel powered ship could, but I think that as the cost of fuel oil goes up, it'll become more economical to switch to nuclear. Might as well jump into at least development now so it's proven and mature by the time it's needed en masse.

As for the LCS... that's a whole 'nother can of worms. Concept is sound, execution is severely lacking.

 

[Vanadium 50]

I am not sure I would want my nuclear freighters flying under just any flag. Moldova? I'm not sure that shipowners want to fly under the US flag either, with the fees and regulations. So this would have to be a lot better, not just a little better.

 

[Vanadium 50]

Marine SMRs may be more practical/realistic - but what would that look like? What kind of power plant?

It's not clear to me how eVinci tuens heat into power to begin with. For various reasons, you probably want to go electric as soon as you can, and drive the screws with electricity, provided you can.

The power per unit volume of the eVinci is an order of magnitude higher than the D2G. So there is space. You want about 100 MW of power. You could do this with 20 eVincis. However, I doubt that is the right approach. I think you want a design like that, scaled up so you need perhaps 4. You want them small enough to get them in and out of the hull with minimum disruption, but you don't want the complexity of having to operate dozens per ship.

It seems to me that it is also not 100% crazy to consider this direction. A submarine gets out of trouble by driving its way out. Typically, it will have one reactor (with a handful of exceptions). The combination means that a reactor problem is a Very Very Bad Thing. Multiple, smaller reactors mitigates this risk.

 

[Astronuc]

It's not clear to me how eVinci tuens heat into power to begin with. For various reasons, you probably want to go electric as soon as you can, and drive the screws with electricity, provided you can.

https://www.westinghousenuclear.com/energy-systems/evinci-microreactor

eVinci is a microreactor, i.e., it is a small reactor 13 MWth converted to 5 MWe (implying 38.4% efficiency). Heat pipes move heat from the core to a heat exchanger, and the heat flows into a working fluid in a Rankine steam cycle, for example.

In the following, the presentation indicates an open air Brayton cycle (34% efficiency)
https://www.engineering.pitt.edu/co...fb89d9fa0ab9e3899/day1-pm3_thomas_tweedle.pdf

The reactor can provide process heat or district heating in remote areas. They do indicate possible use a mining locations, which might be remote from power lines, and an open air Brayton cycle might be practical in dry areas, or areas with restricted or nil water access.

Probably more details here (I haven't reviewed the files).
https://www.nrc.gov/reactors/new-re...vities/pre-application-activities/evinci.html

As gmax137 indicated, submarine reactors have excess reactivity to override Xe following shutdown.

 

[Astronuc]

I am not sure I would want my nuclear freighters flying under just any flag. Moldova?

UK? Austrlalia? I think we're mates.