00X/004 future nuclear CATOBAR carrier thread

[hkky]

Yes, I know all that. The question is can this problem be overcome? Can you refuel with small access ports that won't compromise structural integrity? Fuel rods and control rods themselves are tiny, the coolant is just water. Civilian reactors don't need to worry about keeping the access ports small, but since warships do, can modern technology allow the design of smaller access ports?

Looking at this video, I don't see why the access port can't be made to be as small as basically just a little larger than a fuel rod and it seems like much of the process can be automated. If this can be done, there's also no reason why it wouldn't be used on ships that use HEU either. It would obviate the need to cut large holes in the hull or deck for refueling, even if it's not a big issue as it's only needed to be done once.

During refueling you have to worry about the radiation. If I place a single freshly irradiated fuel rod on the highway and you drive over it at 65 mph, you'd die from the radiation accumulation. So, it is not about physically fitting the fuel through, but also shielding requirements. In commercial reactor refueling, they flood the core and refueling cavity and the fuel always stays >~10 ft below water surface. You can probably get away with 5 ft of water without getting too much dose.

Control rods typically are attached to the core internals (they are not normally replaced and do not come out) but can be inside the fuel if they need be replaced.

 

[Tomboy]

Partially cross-posted from the Chinese marine propulsion thread.

Another one of the two news on nuclear marine propulsion from SOYO on Weibo.

The 004 CVN's reactor housing is likely to be box-shaped, similar to those on the Nimitz and Ford CVNs (probably not exactly news, per se).

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ACP100S in floating nuclear powerplant? Or the rumored nuclear icebreaker or maybe even that 24000 TEU thorium powered container ship. Not a bad development, JN gaining the ability to construct nuclear ships means there's a high chance of dual carrier construction at both JN and DL.

 

[sunnymaxi]

ACP100S in floating nuclear powerplant? Or the rumored nuclear icebreaker or maybe even that 24000 TEU thorium powered container ship. Not a bad development, JN gaining the ability to construct nuclear ships means there's a high chance of dual carrier construction at both JN and DL.

ACP100S is not necessary for floating nuclear powerplant. this reactor is designed by CNNC.

this floating nuclear powerplant project led by CGN(China's biggest domestic nuclear power operator), they have many smaller nuclear reactors, like ACPR50S a 50-megawatt

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(SMR) designed for offshore applications.

Nuclear icebreaker is also a long pending project, China exploring this idea for a long time. now SMR is available so they can start construction. China have big ambitions in Arctic.

if this Jiangnan shipyard nuclear ship news is true, it means China Nuclear shipping era has started.

 

[tphuang]

Larger reactors are cheaper per unit of power generated. The only reason carriers typically have two reactors instead of one is for redundancy.

If they are commercially building a lot of ACP100S (there is also a land ACP100), then they could build a naval variant with supply chain which would lower its cost.

There are not building any SMR that has 250MW

 

[charles18]

Modern reactors like the one on the Ford/Virigina/Columbia are designed to never be refueled in their lifetime hence increasing availability, this is IMO the best way to go for PLAN as well. Next gen nuclear vessels like 095/096(Possibly 093B as well) and Type 004 should all have HEU fueled reactors that never needs to refuel, it increases availability and also decreases lifetime costs as it could cost billions alone to replace the reactor with the associated cost of cutting open the ship etc.

I'm not an engineer but I'm leaning towards the same idea too......HEU. I am assuming HEU uranium does Not chemically or structurally degrade a reactor at a faster rate than LEU uranium.
But....The amount of energy it takes to enrich uranium does Not increase linearly with the enrichment level. It becomes increasingly more difficult, perhaps even exponentially so. Therefore enriching uranium to 90% aka (weapons grade) is very energy intensive and thus an expensive task.
However China has lots of cheap electricity so I'm sure they can make it work. Also the idea of not having to refuel a nuclear reactor seems amazing.

Also another idea is to convert Thorium-232 into Uranium-233 and then put that into PWR reactors at 90% weapons grade. That would give China practically "unlimited" energy.

 

[qwerty3173]

As a nuclear layman, can someone please kindly explain to me why pressurized water reactors are always the choice for ship-born energy? I've heard that other coolants often have better power densities such as molten salts and sodium-potassium melts. Wouldn't a more compact reactor that can work at higher temperatures be better on ships?

 

[ACuriousPLAFan]

As a nuclear layman, can someone please kindly explain to me why pressurized water reactors are always the choice for ship-born energy? I've heard that other coolants often have better power densities such as molten salts and sodium-potassium melts. Wouldn't a more compact reactor that can work at higher temperatures be better on ships?

Pressurized water reactors (PWR) is the most widely used reactor type in the world today.

And for warships usage, typically navies seek technologies that are rather mature and proven (at least, for the PLAN), especially something as crucial as shipboard powerplants (i.e. heart of the ship). Hence, PWR is always the preferred choice compared to molten salt reactors and other types of reactors available today, given that the latter ones are still rather experimental in nature.

 

[gelgoog]

As a nuclear layman, can someone please kindly explain to me why pressurized water reactors are always the choice for ship-born energy? I've heard that other coolants often have better power densities such as molten salts and sodium-potassium melts. Wouldn't a more compact reactor that can work at higher temperatures be better on ships?

Sodium metal burns in contact with water. It is just a dumb thing to put on a ship. There are lead metal reactors as well but historically those have also had issues like with making reliable pumps to pump liquid metal. You also have the issue with liquid metal reactors that if you shut down the reactor, the metal solidifies, and then it is a pain to melt it down again to restart the reactor.

The Soviet Alfa subs used lead-bismuth reactors. That kind of reactor isn't used anymore for those reasons.

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The idea sodium reactors would be a novel thing for naval purposes is also dead wrong. It was tried and decided to be too dangerous.

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[hkky]

As a nuclear layman, can someone please kindly explain to me why pressurized water reactors are always the choice for ship-born energy? I've heard that other coolants often have better power densities such as molten salts and sodium-potassium melts. Wouldn't a more compact reactor that can work at higher temperatures be better on ships?

Size is not a problem even for water cooled reactor in subs. A Russian guy that worked on naval reactors in Russia indicated the reactor itself can fit comfortable in an office sized room.

Using water as a moderator was a choice made Adm. Rickover in the US sub program. Could be multiple reasons, some of which may be,

(1) Sodium as a coolant was evaluated, but in confined space leaks could be a problem since sodium can react with oxygen and water. In the end the metal coolant must dump the heat to generate steam and failure in the heat exchanger would be a problem. Leakage between the primary loop and secondary loop occurs all the time in water cooled reactor without problem. Many of the tubes in steam generators of PWRs are plugged at outage to reduce leakage. Since metal coolant does not need be pressurized, it may be of a lesser problem. Metal coolant may solidify on powering down and may present design challenges. There could also be metal coolant and reactor material compatibility issues.

(2) Water moderated reactor is easier to control and lots of experience

(3) Metal cooled reactor works in high energy neutrons spectrum and can cause much more damage to structural materials than water cooled reactor. Even today, they are having problem finding the right materials. An advantage of fast reactor is its ability to bread new fuel and thus operate to very high burnup, but that would lead to more material damage from fast neutrons.

(4) Naval reactors don't care as much about efficiency as commercial reactors.

 

[Xiongmao]

Talking about safety of nuclear reactors I have a personal story, I once worked with an older colleague who used to be a nuclear engineer from Eastern Europe. He told me that he regularly knew of cases of limb amputations and people being cut in half due to micro-cracks in high pressure water pipes in nuclear plants. The pressure would force water molecules out from these microscopic cracks at incredible speed making an invisible blade as sharp as anything you could imagine. He said there was a certain sound that if you heard while on your rounds, you would stop instantly and not move. These accidents were never made public. The pressure in naval reactors is higher. Although I am sure the materials have improved.