Why is nuclear-powered the standard for submarines, when not for ferry, small ships and vessels ?
In: Engineering
There have actually been four different commercial nuclear powered ships. And a fifth is under construction. But these were all considered research vessels on the feasibility. They all had issues getting permissions to visit harbors and are even not allowed through the Suez canal. In addition you need a lot more time to design the ship as there are a lot more design reviews and certifications. There are also lots of additional safety systems needed including more personnel to manage the reactor and machinery spaces.
The most successful nuclear ships for commercial shipping have been Soviet built ice breakers. These operate in areas with limited refueling capability and require a lot more power then normal ships. In emergencies they might not get refueled at all for months. So even though they are more expensive to operate then a diesel vessels this expense are justified. Even after the fall of the Soviet Union we have continued building these ships. One is about to launch later this year while another two have started construction.
China have announced the construction of a nuclear powered large container ship. If they are successful in proving the concept with new technology and new views on nuclear safety then this might start a change in commercial shipping today away from diesel and over to nuclear power.
The US created a nuclear-powered merchant vessel called the NS Savannah in the 1950s. You can read about its career and why it never took off
Nuclear is a giant pain in the arse. It is expensive, it has proliferation implications, you need very specialised crew, and if you crash you have a nuclear disaster on your hands.
It has only one advantage: it eliminates the need to refuel.
Why does this matter for submarines but not surface ships? You can get a diesel ship with ranges of thousands of miles.
Well to burn 1kg of diesel, you need about 2kg of oxygen. Which needs cryogenic storage, and loves to explode…
If you want to burn diesel long term, you need to access the atmosphere. Which means you stop being a submarine, which means people can find you, which means you die (or the entire point of hiding with nuclear missiles is pointless).
For short range subs however, a mix of batteries and stored oxygen is enough, so European defensive navies love these type of subs.
>why is nuclear power the standard for submarines
It’s not. The top 10 largest sub fleets consist of 354 subs total. Of the 354 120 are nuclear powered. So only about 1/3 of subs are nuclear powered.
Very few ships are nuclear powered for a number of reasons
1. Cost going from conventional to nuclear power will add 1-2 billion USD to the cost of the ship. If were talking about a 10 million USD ferry adding a billion to the price tag is kind of a lot. This doesn’t even count the fact that that ferries maintenance department will now have a pay roll of like 5 million a year. It turns out nuclear technicians and operations officers and safety officers are all kind of expensive. Even the most junior technicians are going to be making six figures.
TL;DR it might be cheaper to run a ferry that literary burned US currency for fuel.
2. Your government will not let you because they don’t want you having nuclear weapons. Unlike a land based reactor it’s almost impossible to refuel a ships nuclear reactor. To do so they have to dry dock the ship and literally cut it in half to access the reactor this takes years and costs hundreds of millions. Therefor they want to minimize how often you do this. As a result the fuel used in a naval reactor is often enriched to 80-90%. This is weapons grade enrichment. A high school physics student together with a shop teacher could make a Hiroshima type bomb with a US navy sub reactors fuel. As you might imagine most governments have issues with normal people having nuclear bombs.
3. You don’t have the tech and the government is never going to give it to you. The rector tech on a US sub is the single most classified technology the US has. In comparison the composition of and how to make the F35’s stealth tech is basically public knowledge. If you want to even see, let alone know how to operate, a naval reactor you need Top Secret / Sensitive Compartmented Information clearance. We share nuclear tech with the UK and Australia. We share sheath tech with 18 countries. You are not going to get the government to sign off on your ferry crew all having higher security clearance than F-22 pilots.
Nuclear is only really the standard for ballistic missile submarines. Their mission is deterrence, they want to cruise around an empty patch of ocean as long as possible without seeing or being seen by anyone or anything, always ready to launch some missiles. Being able to stay deep underwater continuously for months is great for them.
If you’re an attack submarine, it’s not nearly as much of an advantage. Diesel-electric is much cheaper and can be quieter. It may be nice sometimes, so you might build some if you already have nuclear missile subs.
For most other things, it’s way too much of a headache and not really worth the bother.
Being able to stay underwater indefinately is the defining feature. And the military having the expertise to run a nuclear reactor.
Combustion engines can’t operate when submerged. Subs have batteries for when they are submerged, but periodically the sub would need to surface to run the engines to recharge the batteries. A nuclear sub can stay submerged until they run out of stored food.
Ferries and small ships dock every day so they can easily refuel. Nuclear submarines, carriers, battleships, and the like are designed for voyages that last months without returning to port.
Why would you spend 1000x more to implement a design element that aenables ships to remain at sea for months when the ship is going to be docked daily?
India is only the sixth country to develop a nuclear-powered submarine after the United States, Russia, France, the United Kingdom, and China.
So basically 6 countries have it.
Why do ships and ferries not use it? Because it is dangerous and obtaining insurance is impossible
US and Russia tried nuclear powered large ships like a cargo ship.
The ships worked fine, but they realized an issue early on that would make them not possible.
No country wanted a nuclear powered ship in their ports or off their coast.
The military gets away with it because “fuck you”, but merchant shipping doesn’t due to fear of nuclear accidents.
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