Usually the country that owns the sub can't even track it, because they are so quiet, but a lucky sonar operator might pick it up. Actual methods are classified and highly sensitive. Satellites look for heat signatures and sonar systems listen for machinery. SOSUS networks have been laid on the ocean floor at strategic locations to monitor the departure and arrival of submarines into and out of enemy ports. However once the submarines travel beyond the monitoring points, the submarine's location is, as has been mentioned, the results of a proficient sonor operation.
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.
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).
Since its free-fall nuclear weapons arsenal was decomissioned in 1998, the United Kingdom's only means of nuclear weapons delivery is via submarines and SLBMs.
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