The Pentagon's report noted that China has built 12 submarines powered by nuclear reactors since 2009, including two Type 093 and four Type 093A attack submarines, which are conventionally armed ...

To reshape America’s nuclear deterrent and improve maritime capabilities, the US Navy’s first Columbia-class ballistic ...

Nuclear Submarines: Reactor-Powered Turbines & Critical Forgings** The largest fleets of nuclear-powered submarines are held by the USA and Russia, followed by France, China, the UK, and India.

North Korea’s indigenous technological base is clearly insufficient to have developed the submarine on its own—almost certainly meaning that Pyongyang sought help from Russia.