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.
USA has the most nuclear submarines
All submarines can sink. Some can return to the surface.
Argentina had diesel-electric submarines while the British had nuclear-powered submarines.
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.
Ships try to avoid sinking, submarines sink on purpose...
It is doubtful. Canada has never had nuclear powered ships or subs. the current submarines (victoria class) were acquired from the UK and are desiel powered. Canada does not have any plans in the future for any nuclear power vessels.
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
They caused anxiety and sink ships.
No - all submarines, be it nuclear or diesel-electric, use diesel fuel, either for primary engines (DE) or backup generator (nuclear).