7 nuclear power plants for Aus - go LNP!, page-506

Good question.
They are obviously small reactors, however they are not modular. This is a critical difference. Each application in a sub is unique.
This makes them extremely expensive to build.
What I originally said was that the idea came from the marine application. Making them modular is a whole other process including the fail safe features which need to be included.
"The latest versions are walk away safe" In other words if everyone simply left the plant in a panic the plant would shut itself down safely.
For the life of me I dont know why the nuclear industry doesn't publicize these sort of details.
If you research the history of the marine application I believe that you can get a fairly accurate picture of where the nuclear story will go in our world.
The same development, improvements and problems and resistance to change will likely follow or can be avoided as necessary.
Men have been continuously literally living within 100 ft or closer to nuclear reactors since the 1950s in submarines.
All the possible problems are by now well understood.
The scaremongering from the gree nies will one day bring them to justice. They have cost the planet at least 40 years of delays to being sustainable in our existence.
The gree nies invented plastic bags. The number of kids killed by plastic bags is unbelievable. Why didn't they jump up and down and have plastic bags banned?
As I stated above apart from the Russian experiment (some one always has to be the first to learn new technology) no one as died from nuclear disasters or spent fuel. (it not waste, it can and is recycled) The first planes weren't real flash and killed many before they were sorted... But the were sorted...
Even the comments of spent fuel being dangerous for thousands of years is scaremongering. The isotopes which decay in 1 year contain the same amount of energy as the ones which take a thousand years. Which one is really the most dangerous? Why dont the nuclear fraternity point this out....In a lot of cases the spent fuel is about as radioactive as the soil in your back yard....
@Giobria
If you do a search for motive power for submarines it will take you to good places to start It is not a common topic.
I have referred to it as motive power because a reactor is not an engine. It is simply like an electric kettle to boil water to make steam which turns a turbine which is attached to generator to make power which can be stored in batteries or used to turn an electric motor to power the sub.
The kettle is simply the motive power unit part of the equation.
This might be a good place to start...

https://sites.dartmouth.edu/dujs/2013/03/12/nuclear-marine-propulsion-the-history-of-nuclear-techno

hope this helps.