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

[Tam]

My understanding from reading books is that quite large % of noise comes from pumps needed for reactors and one of the biggest advances on newer boats are those passive cooled reactors what dont need any pumps for water circulation.

You always need to have water pumps as a backup in case of emergency or if the natural circulation for some reason isn't working well, even with these natural circulation reactors. But at least when running primarily, you can use natural circulation. Likewise, nuclear reactors that have an active coolant system, are supposed or at least mandated by regulation to have a passive natural circulation backup in case active coolant pumps fail. So natural circulation is a common tech already used in nuclear power plants around the world, even in China.

 

[taxiya]

Just to add, "Natural ciculation" reactors are not designed to run pump-free for the whole power output range. They need pumps when running close to their max output, say the top speed. So the pumps are part of their designed normal operation, not just a fail-safe backup.

 

[taxiya]

2. Some years ago there were articles explicitly mentioning natural circulation used in new sub, which at the time people concluded it was 093.

There was a research paper "Study on Control and Optimization for Natural Circulation Transition Process of Integrated Marine Reactor" from "Naval University of Engineering" 2015.

 

[Tam]

Just to add, "Natural ciculation" reactors are not designed to run pump-free for the whole power output range. They need pumps when running close to their max output, say the top speed. So the pumps are part of their designed normal operation, not just a fail-safe backup.

This too.

Do note that subs have a "tactical" speed around 5 to 10 knots when they are at their quietest.

 

[Tam]

This nuclear reactor has passive circulation features but for a civilian one, the passive or natural circulation is required essential if not by regulation in case if active cooling systems fail. I might speculate that the nuclear reactor for the 095 and 096, as well as future Chinese CV-N maybe based on this reactor. They plan to use it for floating or ship type nuclear power plants.

 

[taxiya]

This too.

Do note that subs have a "tactical" speed around 5 to 10 knots when they are at their quietest.

that is what I called the pump-free operation.

 

[Xizor]

My understanding from reading books is that quite large % of noise comes from pumps needed for reactors and one of the biggest advances on newer boats are those passive cooled reactors what dont need any pumps for water circulation.

You are right. Cooling pumps as well as sump pumps makes a lot of noise. Those who may have aquariums with oxygen pump/ debris cleaners will know that a lot of noise is generated by these systems. You'll realize it once it's midnight when the ambient noise in your room is very low.

Submarines are very noisy (even without the propellers cavitation noise) due to sump pumps, turbine assembly and coolant systems.

Even Diesel electrics can be noisy (even without turbines or nuclear coolant systems).

But Submarines, as most of us know, doesn't need to be 0 decibel silent (it's impossible to achieve). What it aims to is to make as much sound as the ambient noise levels and no more. I read that 70 decibels was the ocean ambient.

Another thing is the dive depth of the submarine. Russian Submarines have enjoyed deeper dive depths than American counterparts. They've also seeked to be redundant in systems (unfortunately this has degraded the noise levels versus the American subs).

 

[Anlsvrthng]

You are right. Cooling pumps as well as sump pumps makes a lot of noise. Those who may have aquariums with oxygen pump/ debris cleaners will know that a lot of noise is generated by these systems. You'll realize it once it's midnight when the ambient noise in your room is very low.

Submarines are very noisy (even without the propellers cavitation noise) due to sump pumps, turbine assembly and coolant systems.

Even Diesel electrics can be noisy (even without turbines or nuclear coolant systems).

But Submarines, as most of us know, doesn't need to be 0 decibel silent (it's impossible to achieve). What it aims to is to make as much sound as the ambient noise levels and no more. I read that 70 decibels was the ocean ambient.

Another thing is the dive depth of the submarine. Russian Submarines have enjoyed deeper dive depths than American counterparts. They've also seeked to be redundant in systems (unfortunately this has degraded the noise levels versus the American subs).

Deeper dive means the cavitation noise will be smaller around the propeller, so the same design can go faster.

Means deeper diving submarine has less noise.

The most loud noise source should be the evaporator , fast moving steam and water in the pipework, rotating turbine, lubricant oil pumps and so on. Condense water pump doesn't need to be noisy ,at least not more than the steam tubine.

 

[Xizor]

Unsurprisingly, Metallurgy again dictates Hull strength and therefore Max dive depth of the Submarines.

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Japan, Germany and US continue to remain at the forefront of this (obviously). Russia sidestepped (kind of) by application of its vaunted Titanium reserves.

But is Mariana trench the limit for deep diving?
Other than the Hull strength (dictated by metallurgical progress), there is another factor that might (? When factoring in the costs sunk on the Metallurgy and manufacture of a submarine) prevent nations from demanding that Submarines dive deeper. The SOFAR channel.

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The SOFAR channel is a particular depth at which sound is able to propagate at great lengths (because of the conflux of certain factors like pressure, temperature and salinity which in turn affects sound wave propagation). Usually it's about 600 to 1000 m depths.

 

[Tirdent]

Not all of those alloys have ever been used at large scale though - by this I mean large in hull numbers (at least for the country concerned) and also hull size. Building one or two 8m³ bathyscaphe pressure vessels is a very different ball game than a dozen 7000m³ SS(B)N pressure hulls (that Chinese titanium alloy is a case in point). By this standard France and Russia are in the lead, having used HY130-equivalent steels in significant quantities of frontline nuclear submarines.