I wonder if it's possible and/or worthwhile to design CVNs for frequent refueling. Refueling every 18-24 months in and of itself isn't a big deal, modern reactors can do that in ~1 month's time and a ship probably spend at least that much time in port for refit every 2 years anyway. It's really the difficulty of refueling a CVN that's the problem. Can a CVN be designed to be refueled as easily as a civilian reactor? Would the tradeoffs be worth it?
00X/004 future nuclear CATOBAR carrier thread
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I wonder how tightly packed the TRISO fuel is. Its shell should be pretty hard, so if they're tightly packed and there isn't much movement of the pebbles then maybe it's possible?
You'll risk structural integrity; military ships are built for high survivability by adding huge access ports that cut through multiple decks is a bad idea for both structural and space efficiency since you'd have to shuffle stuff around. If they actually use 4 reactors, then you'd need 4 massive reactor sized holes all the way from the flight deck to the very bottom of the ship which I don't really have to say for people to know why this is a terrible idea.
Civilian ships don't really care about that because getting struck by missiles and bombs isn't really a part of their design considerations, plus no civilian ships use LEU reactors for propulsion(Russian nuclear ice breakers/cargo carriers use 20-90 percent enriched HEU for their reactor hence refuels once every 10 years or more for the ones that use higher enriched fuel). For floating power stations, it probably doesn't matter because they are designed to have their reactor highly accessible for fast refueling anyways.
Technically it isn't true, the Soviet KLT-40 family of reactors for use on merchant ships/ice breakers and floating powerplant has two variants with one capable of using both 30-40 percent enriched fuel and 90 percent enriched fuel and another one that could use <20 percent enriched fuel. Hence it is actually possible to modify a reactor design to accept higher/lower enriched fuel.
French naval submarine and carrier reactors supposedly use low enriched fuel.
"Paris has nuclear technology, which powers the Charles de Gaulle and all of its submarines, but France uses low-enriched uranium (LEU) at less than 20%, a level similar to that used in nuclear power plants for electricity generation. LEU uranium must be renewed every 10 years, a delicate and dangerous operation, but it cannot be diverted for military purposes.
American and British submarines use highly enriched uranium (HEU), which is more than 93%. Its lifespan is 30 years, but precisely because it is enriched, it can be used to make a bomb."
"Paris has nuclear technology, which powers the Charles de Gaulle and all of its submarines, but France uses low-enriched uranium (LEU) at less than 20%, a level similar to that used in nuclear power plants for electricity generation. LEU uranium must be renewed every 10 years, a delicate and dangerous operation, but it cannot be diverted for military purposes.
American and British submarines use highly enriched uranium (HEU), which is more than 93%. Its lifespan is 30 years, but precisely because it is enriched, it can be used to make a bomb."
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.
A HEU reactor still operates at the same temperature and pressure as a LEU reactor about 330 celsius or a little less.
It still produces the same horsepower per unit volume.
Perhaps the core as in the (fuel rods and control rods) are of a different design but.....wouldn't everything else like the:
reactor
pressurizer
heat exchanger
water pumps
still essentially be the same?
It seems HEU and LEU reactors have A Lot more in common than they are different.
BTW I'm not saying the Type 004's reactors are based off ACP100S.
That's Top Secret info. Who knows?
Yeah, they use 7% to 10% LEU for their reactors as part of the commitments for the NPT. As mentioned, the downside is more frequent refuelings compared to HEU reactors, though
Understood your your position on ACP100s.
What you are saying is an airplane is an airplane, they have common functional parts.
Different commercial reactor designs do not operate at the same power density. That's why some pressurized water reactors can operate 24-month cycles while others are stuck at 18-month. To some extent this is also a question of economics since longer cycle length will require more fresh fuel be loaded each time. Economic would not be a concern for subs. PWRs have higher power density to BWRs.
A naval reactor likely does not operate at same temperature as a commercial reactor. As far as I know, Rickover chose zirconium as the fuel cladding material. Unless it is very thick, it would not last 20 years at commercial reactor operating temperature. Bettis (US naval reactor design organization) have published papers on zirconium hydrogen pickup research, which would mean they are not using thick cladding.
Spent fuel is highly radioactive, also military naval reactors are designed to be as compact as possible for the same power output so there are some sacrifices like the entire core is designed as a single unit and must be replaced all at once. Also refueling isn't as easy especially for a naval vessel as you think, Russian icebreakers use a method like you described(At a expense of less power dense core) however it still took months to complete the cycle(Which is better than 2-3 years for CVN with an integrated core design) but considering they refuel once 7-10 years it still adds up over a 50 year lifespan. 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.
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).
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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