Under the worst possible conditions, a meltdown can occur in a nuclear submarine. It is an event of low probability, however.
coz if nuclear meltdown it can explode
USA has the most nuclear submarines
a nuclear reactor had a nuclear meltdown
Argentina had diesel-electric submarines while the British had nuclear-powered submarines.
Russia
Chernobyl, Russia
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
Human stupidity
Chernobyl