Why is nuclear-powered the standard for submarines, when not for ferry, small ships and vessels ?
In: Engineering
Nuclear reactors allow submarines to stay submerged for longer periods of time, which is a great advantage for a submarine. They’re also expensive and require the submarine to have radioactive material on board, which makes the submarine much more expensive to make (you also need to have ways to shield the crew from radiation.)
It makes sense to build a reactor on a submarine, and it makes sense to build them on massive ships like aircraft carriers… but you wouldn’t go to the expense of putting in a reactor on a small boat.
They are not. Only 6 nations run nuclear submarines and they are almost only for large military submarines (which often carry nuclear weapons).
Diesel electric submarines are far more easier and cheaper to build. The big advantage of these nuclear powered submarines that they can submerge for very long times (basically as long as the crew has food) and therefore can stay hidden. That’s interesting for military applications.
For anything else Nuclear power is a highly expensive and restricted technology. Basically it’s not economical for most kind of vessels.
It’s more expensive.
For naval ships, nuclear power is interesting because it has major range advantages. One of the first things the US tried once it assembled a fleet of nuclear ships was a 65-day trip around the globe with no stops for refueling. That’s a big deal if you’re a ship that wants to patrol in hostile waters very far away from a friendly port. And for capital ships like aircraft carriers, the power needs are so great nuclear makes a lot more sense. It also helps that a military can keep highly trained staff employed to maintain reactors.
Most vessels don’t work like that. They go along well-planned trade routes and part of their business is making stops. It’s not a big deal to refuel and do minor maintenance while their cargo is being loaded and unloaded. You don’t need quite as specialized engineers to work on diesel engines. You don’t have to worry about pirates seizing small reactors and doing stupid things with them. The list goes on and on.
Nuclear power is prohibitively expensive. And complicated. Plus it would be dangerous to have Joe the ferry operator sailing around with radioactive material.
It gives subs the capability to stay underwater for much longer. Which is a major benefit. Most applications it’s not really worth it.
For most applications it’s better to just have normal engines that are easy for average workers to work on. You could basically get some basic maintenance done anywhere in the world.
Non nuclear subs need some sort of combustion engine. That needs oxygen to burn and some way to expell exaust gasses. So when when the engine is running they need a snorkle at the surface and when they dive they are on battery power.
Relevant post on r/submarines https://www.reddit.com/r/submarines/s/amMzTXhQ4c
Nuclear is absolutely not the standard for submarines and those that use it, only run on nuclear despite the massive costs and complexity, because it has very unique strategic advantages over traditional powering methods
Aircraft carriers also like nuclear because the nuclear reactor produces tons of steam. This steam is used for the catapult launch system.
Non-nuclear carriers either use the ski-jump ramps, severely restrict payloads, or both.
Nuclear power is also used on icebreakers.
[https://en.wikipedia.org/wiki/Nuclear-powered_icebreaker](https://en.wikipedia.org/wiki/Nuclear-powered_icebreaker)
For ships that need to go to ports in different countries, there is to much political hassle with nuclear propulsion and armed security that nuclear powered ships need.
well, for one your security concerns are helped by a nuclear sub being a military vessel and not some random ferry operator securing nuclear material
To add on to what others have said, the reactors in nuclear subs need to be fairly small to fit into the boat. That in turn means those reactors run on highly enriched uranium, which puts you very close to nuclear weapons. Depending on the political situation, that may be cause for serious concerns amongst other nations.
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