OT Nuclear U-Boats; how do they condense the steam?

gareth evans · 2021-09-16T13:49:28+00:00

After following the Vigil TV series (with all itsreported errors) and also the prog on HMS Trenchard,when a Brit U-boat is powered by nuclear fuels, howdo they condense the steam?With sea water? If so, there must be difficultiesin sealing the intakes and outfalls from deep seapressures.Perhaps the steam is heated to 200C and only cools to100C through the turbines before recirculatingso no condensing isrequired. This, of course, will be wastefulof some thermodynamic energy, but there's so muchin reserve in the nuclear fual that perhaps it does notmatter.

Sep 16, 2021 Last reply: 5 years ago 64 Replies

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The Natural Philosopher 5 years ago

If it were that easy we wouldnyt bother with subs at all.

Its been done. In fact I worked on it back in the 1970s. rubber coated hulls, very slow propellors, down deep. Totally undetectable.

Same goes for thermal signature. You cant 'see' it through a lot of layers of water . And teh sub can run on batteries even if its a nuke,

I can assure you, they do, but I can also assure you, that a sub sitting at depth with engines off is almost impossible to detect. And there are limits to how much of the sea you can litter with sonobuoys.

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Dimitris Tzortzakakis 5 years ago

???? 16/9/2021 4:49 ?.?., ?/? gareth evans ??????:

well, the expected answer is with sea water, the same "coolant" that convential ships use. I read once a german article about the sinking of the US submarine "Thresher", that was designed to go deeper thna usual, and that was not combined with welding of its pipes, instead of soldering, to withstand the higher pressures involved, also they needed a "clean room" to work, so it's possible that a speck of dust sank the

300 m submarine! Also that it needed a more powerful air compression system, so it could "blow" its ballast tanks in distress, especially following a reactor SCRAM.

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newshound 5 years ago

Two theories, one official and one unofficial, are very well described here.

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It is true that the Thresher had brazed heat exchangers, which showed faults in subsequent boats. I don't see any justification for the "speck of dust" claim and I don't think the Thresher was particularly designed for deeper diving, although this aspect of performance is normally classified. It has been surmised that they were unable to "blow" the tanks because of ice crystals blocking the lines.

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Tim Streater 5 years ago

I thought the sequence was:

1) Brazed joint fails allowing ingress of sea-water while they were at test depth.

2) Sea water shorts some circuits leading to reactor scram

3) Attempts to blow tanks fail because expanding air cools so much that moisture within it freezes and jams the valves, preventing blowing of tanks

4) Lack of reactor power prevents boat being driven towards surface using engines, boat sinks instead

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newshound 5 years ago

Yes, that was the official theory. I believe another error was that there were still debris strainers in the air lines that should have been removed after commissioning, and that these contributed to the blockage by ice crystals. I think it is more likely to have been pipe blockage than valve jamming, you would only get crystals once the valves were open and the air was flowing.

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