09V/09VI (095/096) Nuclear Submarine Thread

[Tam]

Forget RTG generation. It generates too little power for a submarine. Also, the heat generated is low grade heat so the conversion efficiency into motive power is really low (think Carnot cycle). Even if you use alternative methods to convert the heat into power, say thermoelectric generators, the conversion efficiency of the heat into electricity is like 15%. RTGs are mainly useful for things like sonar buoys in the middle of nowhere. Think of it like a long duration backup battery for some device you will not have easy access to. Also Strontium-90 is really problematic because it is a beta emitter and it is highly carcinogenic. There is a reason why people typically stick with the much milder alpha emitter isotopes.

I think the LWRs are still the best choice. It might be possible to use some other way to convert the heat into motive power. But other than that there are not a lot of choices with regards to reactor design given current technology. There are other reactor designs, for sure, but they have their own issues. The Soviets used lead-cooled fast reactors in the Alfa-class submarine for example. But it has a lot of issues, like, when you power it down the coolant solidifies and then you need to melt it down with heat before you start the reactor again. It is a real issue and made them go back to LWRs in later series. Sodium-cooled fast reactors are a no-no in a submarine. The sodium coolant burns in contact with water. Then there are things like pebble-bed and prismatic nuclear reactors. Of those I think the prismatic nuclear reactors make the most sense. But their main advantage is to have lower weight and be more compact. Which is not that big of a deal for something like a submarine. I think the advantage of sharing much of the technology with civilian nuclear reactors make LWRs the most practical choice.

Lead cooled can be safe. If it leaks, it does not evaporate into the atmosphere but pools into the floor and cools into a solid.

 

[Anlsvrthng]

Forget RTG generation. It generates too little power for a submarine. Also, the heat generated is low grade heat so the conversion efficiency into motive power is really low (think Carnot cycle). Even if you use alternative methods to convert the heat into power, say thermoelectric generators, the conversion efficiency of the heat into electricity is like 15%. RTGs are mainly useful for things like sonar buoys in the middle of nowhere. Think of it like a long duration backup battery for some device you will not have easy access to. Also Strontium-90 is really problematic because it is a beta emitter and it is highly carcinogenic. There is a reason why people typically stick with the much milder alpha emitter isotopes.

The radioisotopes has the same heat "quality" like the reactors.
The main reason why no one use them is the cost of manufacturing ,handling and the small available quantity .

That is the reason why the strontium 90 is the only candidate, the other available is the Cs137, and that is gamma emitter.
But even with Sr90 it is still only possible to make only (few) dozen of submarine, with cost higher than associated with reactors.

I think the LWRs are still the best choice. It might be possible to use some other way to convert the heat into motive power. But other than that there are not a lot of choices with regards to reactor design given current technology. There are other reactor designs, for sure, but they have their own issues. The Soviets used lead-cooled fast reactors in the Alfa-class submarine for example. But it has a lot of issues, like, when you power it down the coolant solidifies and then you need to melt it down with heat before you start the reactor again. It is a real issue and made them go back to LWRs in later series. Sodium-cooled fast reactors are a no-no in a submarine. The sodium coolant burns in contact with water. Then there are things like pebble-bed and prismatic nuclear reactors. Of those I think the prismatic nuclear reactors make the most sense. But their main advantage is to have lower weight and be more compact. Which is not that big of a deal for something like a submarine. I think the advantage of sharing much of the technology with civilian nuclear reactors make LWRs the most practical choice.

Every reactor design has its challenges during the prototypes / early uses. The US BWRs has the same teething issues like the CCCP liquid metal reactors.
Only difference was Russia didn't wanted to continue the development.

Every reactor is usable, if enough experience collected, but it is expensive. US spent only one reactor typed, and two for commercial.
CCCP/russia has two submarine (one matured) and four commercial ( two matured, one in final development phase) and one further (lead cooled scaled up Alpha reactor) under commercial development early phase.

China is in the early phases on the development, and the second reactor type (if you can trust the news) will be molten salt : )

That is the most compact, safest reactor design, very good for submarines.
However that will takes lot of time to master it.

 

[gelgoog]

There is a difference in heat quality yes. An RTG pile produces much lower temperatures. An RTG will not be able to boil water and hence you cannot use a steam turbine with one. Also given the Carnot efficiency of heat engines it will always be worse than a regular nuclear fission reactor because it is lower temperature. It has a much lower energy production per unit of mass compared to a LWR. Because of the low temperature you can only use thermocouples or Stirling engines with either the heat->electricity conversion is pretty awful.

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Look at the tables on bottom. Notice the Watts/Kg. Even the best RTG pile in those lists output less than 1 kW of electricity. A submarine reactor needs like tens or hundreds or megawatts to operate. That is like 10 000x more power. Then there is the matter of handling that fuel. No sane person would use Strontium 90 in large quantities for any kind of application. Not when there is the risk of getting into physical contact with it. In comparison you can handle brand new uranium or plutonium fuel rods with just a pair of rubber gloves.

Molten salt reactors also make zero sense for submarines or marine reactors, like I said before, sodium burns in contact with water. It is a catastrophe waiting to happen.

The lead cooled fast reactors have decent market prospects but mostly for land applications, not marine applications. No one wants to be marooned in a submarine which cannot start its engines because the coolant solidified. That is what made the Russians abandon the design.

 

[Anlsvrthng]

There is a difference in heat quality yes. An RTG pile produces much lower temperatures. An RTG will not be able to boil water and hence you cannot use a steam turbine with one. Also given the Carnot efficiency of heat engines it will always be worse than a regular nuclear fission reactor because it is lower temperature. It has a much lower energy production per unit of mass compared to a LWR. Because of the low temperature you can only use thermocouples or Stirling engines with either the heat->electricity conversion is pretty awful.

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Look at the tables on bottom. Notice the Watts/Kg. Even the best RTG pile in those lists output less than 1 kW of electricity. A submarine reactor needs like tens or hundreds or megawatts to operate. That is like 10 000x more power. Then there is the matter of handling that fuel. No sane person would use Strontium 90 in large quantities for any kind of application. Not when there is the risk of getting into physical contact with it. In comparison you can handle brand new uranium or plutonium fuel rods with just a pair of rubber gloves.

?
Decay heat from an isotope can reach any temperature, it depends only on the heat transfer efficiency.
What do you think, what melted the rector core in Fukushima and Chernobyl ?
The RTGs works with above 600 Celsius on the warm side usually.
RTG preferred technology because it doesn't take the risk of overheating of the isotope and example boil it out .
But there is no technological reason why not to use it instead of rectors, apart from economic factors, like :
1. single submarine require hundreds of GW range reactor years to make.
2. Require reprocessing/handling capacity bigger and more expensive than required for nuclear programs.

Molten salt reactors also make zero sense for submarines or marine reactors, like I said before, sodium burns in contact with water. It is a catastrophe waiting to happen.

Interesting, do you know the cooling material of a molten salt reactor?
Just to give a guess : it is not liquid metal sodium.
It is molten salt : D

The lead cooled fast reactors have decent market prospects but mostly for land applications, not marine applications. No one wants to be marooned in a submarine which cannot start its engines because the coolant solidified. That is what made the Russians abandon the design.

They abandoned it because they didn't made any new submarine, and for new ones they can not afford two competing technology.
The solidification was a solvable technological issue, on the new generation they could solved it, but there was no new submarines after the alphas .

 

[Tam]

The lead cooled fast reactors have decent market prospects but mostly for land applications, not marine applications. No one wants to be marooned in a submarine which cannot start its engines because the coolant solidified. That is what made the Russians abandon the design.

As already mentioned, that can be solved by technology or simply keep the reactors running, which is what the Russians did with the Alfas. Despite the notorious safety issues the Russians had with PWR nuclear submarines, one of which is made into a movie, the Alfas with their lead reactors had a relatively better safety record than the rest of the fleet. If you remember these are small subs that displace only as much as a Kilo but can go 41 knots underwater.

Should something happen, lead is not going to escape into the atmosphere. If the lead solidifies around the core, then you have in effect, a self sealing nuclear reactor. Lead also acts as a barrier against radiation. If a sub is marooned and on the surface, it will have to just call for help. But the main priority is that the crews are safe and the sub is not contaminating the environment.

The real problem is when the sub is decommissioned, and when you can't easily dismantle the reactor and reuse the fuel somewhere else. You will have to remelt the frozen core to extract the fuel.

 

[Tirdent]

Ok Deino, last one from me.

I don't see how suddenly changing to a new small class would be cheaper than a larger one that is already on production. You may end up making smaller but more expensive subs versus bigger but cheaper submarines because the later has been volume produced. With every new Yuan, the price for each unit goes down.

That's a misinterpretation of economy of scale. In this context it does not affect *recurring* production cost (material, labour etc.), that aspect is driven almost completely by sheer size of the boat and making it smaller will generate significant advantages. While *non-recurring* production cost (R&D, infrastructure etc.) for a 2000t sub will indeed not be greatly different to a 4000t design, much of it (processes, scalable systems, software etc.) is already paid for by the Yuan and S20 projects. A domestic AIP S20 WILL be cheaper than a Yuan by a healthy margin, count on it - and that's before you consider *operating* cost (crew, training, fuel, maintenance etc.).

Alternatively, if we agree that a large fleet of competitive Chinese SSNs is a good few years away still, it may boil down to a choice between a clean-sheet ~4000t or clean-sheet ~2000t SSK as an all-new successor to Yuan. That again favours the smaller design in terms of cost.

This is like the guy who ran the track and gets the record because he choose to make it public, even if others may have ran the track faster but kept it secret.

Well - maybe, maybe not. In any case, this provides no indication your assertion that in a littoral scenario with short transit a 4000t SSK still improves on the endurance of a 2000t boat by enough of a margin to make its increased cost worthwhile holds true.

China has 40GWe reactor capacity, so by reprocessing all waste from them it is possible to start maybe 7 submarine, with 1 MW thermal capacity each.
It is possible to increase the number maybe to 12 with Sr90+Cs137.

Thanks for that back-of-the-envelope calculation, does indeed not appear to make sense then.

Look at the tables on bottom. Notice the Watts/Kg. Even the best RTG pile in those lists output less than 1 kW of electricity. A submarine reactor needs like tens or hundreds or megawatts to operate. That is like 10 000x more power.

The idea is not to create an SSN but to drastically cut cost by sizing the nuclear plant as an AIP replacement for a SSK that delivers only enough power for slow patrol speeds. Going by established AIP systems that requires maybe 200 - 300kWe, i.e. no more than 1.5MWth (assuming a conservative estimate for the efficiency of a Stirling engine).

Read Anlsvrthng's posts again, his figures are realistic and show the idea falls down more on logistical considerations than anything else.

 

[Hendrik_2000]

Not sure about the credibility of this news Via JSch

From Sina Military weibo.

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来自

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【官方确认中国新一代核潜艇研制：荣获中国工业最高奖】12月9日，第5届中国工业大奖表彰大会在北京举行，被誉为中国工业“奥斯卡”的第5届中国工业大奖获奖名单也正式揭晓。中国船舶重工集团公司第七一九研究所的新一代核潜艇研制项目获得中国工业大奖。
Sina military
Today 12:40 from Weibo
[Official confirmation of China's new generation of nuclear submarines: won the highest award in China's industry]
On December 9, the 5th China Industrial Awards Commendation Conference was held in Beijing. The winners of the 5th China Industrial Awards, which is known as the "Oscar" of China's industry, were also officially announced.
The new generation nuclear submarine development project of the 719th Research Institute of China Shipbuilding Industry Corporation won the China Industrial Award.

 

[Hendrik_2000]

This design might not be type 95 thought It could be the much talk about of conventional submarine with piggy back small nuclear power plant to take care of the service duty like the one presented on Tsinghua student by the ex procurement chief of the navy
Maybe some one can posted the slide presentation I know it is somewhere in the submarine thread

 

[gelgoog]

Assuming that is the design it looks a lot more advanced than what they have now. It kinda looks like an HDW diesel-electric submarine though.

 

[SinoSoldier]

Not sure about the credibility of this news Via JSch

From Sina Military weibo.

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来自

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【官方确认中国新一代核潜艇研制：荣获中国工业最高奖】12月9日，第5届中国工业大奖表彰大会在北京举行，被誉为中国工业“奥斯卡”的第5届中国工业大奖获奖名单也正式揭晓。中国船舶重工集团公司第七一九研究所的新一代核潜艇研制项目获得中国工业大奖。
Sina military
Today 12:40 from Weibo
[Official confirmation of China's new generation of nuclear submarines: won the highest award in China's industry]
On December 9, the 5th China Industrial Awards Commendation Conference was held in Beijing. The winners of the 5th China Industrial Awards, which is known as the "Oscar" of China's industry, were also officially announced.
The new generation nuclear submarine development project of the 719th Research Institute of China Shipbuilding Industry Corporation won the China Industrial Award.

So, nothing that we didn't already know.

The CG is also from a few years ago and unofficial.