The PLA navy has more than 225,000 personnel and is thought to have as many as 70 submarines, 10 of them nuclear-powered
The US, Russia, Great Britain, France, China and (recently) India have nuclear submarines.
As of October 2023, the countries known to possess nuclear submarines include the United States, Russia, China, France, and the United Kingdom. The United States has around 68 operational nuclear submarines, while Russia has approximately 60. China operates around 12, and both France and the United Kingdom have about 10 each. India is also developing its nuclear submarine capabilities and has launched its first operational vessel.
From Wikipedia: Today, six countries deploy some form of nuclear-powered strategic submarines: the United States, Russia, France, the United Kingdom, People's Republic of China, and India Several other countries, including Argentina and Brazil, have ongoing projects in different phases to build nuclear-powered submarines.
230
170
USA has the most nuclear submarines
nearly 155
Argentina had diesel-electric submarines while the British had nuclear-powered submarines.
Reactors power submarines and many surface ships. Nuclear weapons.
Sixty to Seventy is the consensus estimate.
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.