US, USSR, Red China, Great Britain, and France have bona-fide atomic subs, taht is submarines powered by Nuclear reactors. all of these powers also have atomic and in some cases conventional, ( Russia has some) submarines which are equipped with long range nuclear missiles- such as Polaris, Poseidon, Trident, which are properly Missile types rather than submarine types.
USA has the most nuclear submarines
Argentina had diesel-electric submarines while the British had nuclear-powered submarines.
A number of nuclear submarines sank, and the circumstances vary from accident to accident. Wikipedia has a list, and by going there and entering "List of sunken nuclear submarines" you can review that list.
Nuclear submarines are powered by a nuclear reactor and they are completely independent of air, so there is no need to surface frequently.
The US, Russia, Great Britain, France, China and (recently) India have nuclear submarines.
The primary mission of the fleet ballistic missile submarine is deterrence. By deploying these submarines, we are sending aggressor nations a message. That message is that we have nuclear and other strategic weapons on a platform that can be positioned just about anywhere in the ocean and used to retaliate against any nation that is overtly aggressive toward us or our allies.
There were tests of nuclear weapons but no other nuclear weapons were dropped on other nations as an act of war. Hiroshima and Nagasaki are the only uses of atomic weapons on other nations.
Yes, nuclear submarines generate nuclear power. There is a nuclear reactor on board (hence the tern nuclear submarine) which creates steam to drive the main engines to turn the screw(s).
Nuclear Energy
The PLA navy has more than 225,000 personnel and is thought to have as many as 70 submarines, 10 of them nuclear-powered
Plutonium can be used in nuclear reactors for nuclear propulsion of ships and submarines.
No - all submarines, be it nuclear or diesel-electric, use diesel fuel, either for primary engines (DE) or backup generator (nuclear).