The US uses nuclear power aircraft carriers. Is this efficient? What are the drawbacks? Could the same systems theoretically be used in cars?
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The benefits of nuclear power on a large naval vessel are numerous, both in terms of how much energy can be generated and the removal of a refueling requirement. Well technically it needs to be refueled every 25 years, but that beats the need for diesel tenders or nearby ports. It’s also not very polluting, which is a nice side-benefit, but not the primary military focus. For an aircraft carrier the ability to be free from fuel requirements means that shore leave and food stores are the limiting factor on a deployment, and the latter can be served by mid-mission supplies by helicopter or a specialized rope system between two boats. For a submarine nuclear power means that they can stay submerged for as long as food and crew morale holds out.
The downsides are the cost, the technical complexity and the need for highly trained staff to maintain the onboard plant. For a sub the downside is also that some noise can’t be entirely eliminated; you can shut down a diesel plant, but you can’t shut down the cooling pumps to a nuclear pile.
As for cars yes it can THEORETICALLY be used and there was an attempt a long time ago, but it’s a bad idea and was scrapped. The weight of a properly shielded reactor is not trivial, accidents happen and that would add cost and complexity to the cleanup, and it would be a terrible proliferation risk. It’s also inefficient to have millions of small reactors rather than large power plants which can energize a grid and charge battery-powered EV’s.
There are approximately 6 million automobile accidents per year in the United States alone. That’s an awful lot of potential nuclear accidents. That reason alone is why a nuclear powered car is a very bad idea.
Another reason is that nuclear reactors are essentially big steam engines. Put enough radioactive material close to each other and things get hot. Put them under a boiler and you produce steam, which turns whatever you need it to turn to generate electricity, spin the impellers, turn the screws, etc. Automobiles have had steam engines before, and they didn’t work out too well.
Nuclear reactors do not require frequent refueling like combustion engines. You typically refuel them during refits, about once a decade, rather then constantly. That means that the aircraft carriers can operate for weeks without any supply ships or even years if they get supplied with food and ammunition from cargo aircraft. The nuclear reactors are however large, expensive and complex systems. So they require a lot of buoyancy and crew. Even the smallest and lightest nuclear reactors we have could not even fit on a locomotive, although there are efforts of making them smaller. There is also a lot of radioactive material in the nuclear reactors so that you need to take care when decommissioning the ship so as to prevent radioactive contamination of the environment. This is especially challenging if the vessel gets sunk either on accident or on purpose. So far there are several nuclear powered vessels which have been sunk and fortunately we have not had any significant environmental impact from them but we might end up contaminating some area of the ocean with radioactive materials. Still a better track record then oil tankers though.
The problem is that is very expensive, needs specially train crew to manage them, and need to be disposed of with a car when you decommission the carrier.
The advantage is they can provide a lot of power for a very long time duration so carriers can move at high-speed years without the need to refuel. On a submarine, the advantage is even larger because not oxygen and fuel is used and no exhaust is produced so you can stay underwater until you run out of food. You can make oxygen from seawater for the crew.
The US only uses nuclear power on carriers and submarines. They did have nuclear power cruisers before but they were to expensive to operate. That tells you something about the feasibility of a car. A few nuclear-powered cargo ships have been tested, but the have been too expensive to operate.
Nuclear power work by heating up water to steam and ut it on a gas turbine. The water then needs to be cooled or replaced with new water. Nuclear power is steam power with a different type of heat source. Add to that you need shielding around the reactor to protect humans from the radiation. Reactors need to be cooled after you use them we talk about active water cooling for weeks for nuclear power plants. The water pump needs an external energy source
Cars are often in accidents and you do not what to break apart and leak out radioactive material. You transport spent nuclear fuel in a container like https://bloximages.chicago2.vip.townnews.com/journalstar.com/content/tncms/assets/v3/editorial/d/67/d6729e0b-0652-553f-9634-12efb2dd3353/d6729e0b-0652-553f-9634-12efb2dd3353.image.jpg that do not break in a crash or a fire. You do not transport fuel that has just been used in a reactor, you keep it in spent fuel pools for a couple of years so the amount of heat they generate from nuclear decay is refused.
So a nuclear reactor in a car is a terrible idea. You can use energy from nuclear reactors to power a car. Generate electricity or perhaps hydrogen in a stationary power plane and use it to power a car.
So nuclear reactor on something that moves will be for ships and just a few types of military vessels. There are some nuclear ice breaks but I do not think they are really cost-efficient. Nuclear power also possible for space ships to move out in space. But that is where it is a good idea.
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It’s decent for ships, at some point in ship size it becomes easier to fit in a nuclear powerplant than a fuel tank big enough to hold fuel for a month or whatever it needs between port visits.
Cars are nowhere big enough for that. Also a ship is in the water, giving it infinite cooling for the reactor.
The energy density of nuclear fuel is so ridiculously huge. There are nuclear powered ice breakers that use so much energy that they literally cannot run on diesel because there isn’t enough room for the fuel! (possibly this is slight exaggeration).
I don’t know if efficiency is the right word, it could be diesel engines are more efficient that nuclear, but the energy in nukes is so much higher it wouldn’t matter. The major downside is size and complexity of the power plant. Nuclear power remember is just heat. So you have to boil water first then use that to push the ship using electrical motors or some other way of converting steam energy to rotating the screws of the ship. An internal combustion engine can turn the screws directly.
You could use them in cars yes. Probably not worth the risk.
IIRC, there was a design for a US military aircraft that was nuclear powered, but they couldn’t properly shield the pilots from the radiation.
If you’re just protecting your own waters, diesel fuel is just fine. But the US is sending air craft carriers around the world. That creates a logistical fueling nightmare. The constant need to be sending supply ships with fuel on a regular basis, and that an enemy need not take out the air craft carrier, but instead simply attacks its supply lines.
As it is they need to refuel for planes and food. But nuclear power allows the ship to run for decades w/o needing it’s own refueling (just aircraft fuel and food).
Cars on the other hand are often in accidents and we don’t want a nuclear accident during rush hour in populated areas. Aircraft carriers are designed for being attacked so there is much less chance of an accident. And if there was the reactor would just sink to the bottom of the ocean away from people.
Nuclear reactors are basically piles of radioactive material that gets hot. Heat boils water and water makes electricity. There’s plenty of water of course, and electricity is really useful for running everything, including the engines and ship systems like radar.
Nuclear fuel has a lot of energy in a relatively small amount of material. This means that the nuclear reactor can last literally years without needing any refuelling.
There were proposals to make nuclear cars but never got past the concept stage. Trouble is, nuclear power is expensive, and potentially dangerous if mishandled.
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