A nuclear-powered submarine carries a small reactor that generates its own electricity, oxygen, and heat, meaning the submarine can stay deep underwater for as long as the food lasts to feed the crew. This submarine can travel faster and farther than a diesel submarine. So, for military planners in the US, ROK, Taiwan, or Japan, this particular submarine poses a grave threat.

Theoretically this underwater vessel (estimated to weight 8,700 tons) can sail across the Pacific Ocean and sit off the coast of California, Taiwan, Japan, anywhere, ready to fire missiles, without anyone knowing it is there. If North Korea has a submarine hidden deep in the ocean, this vessel guarantees that any country attacking North Korea would suffer damage in return.

In September 2023, North Korea launched a submarine named 'Hero Kim Kun Ok'. While that vessel could carry nuclear missiles, it was still powered by diesel engines. ROK anti-submarine systems are designed to locate and track noisy diesel submarines, not quiet nuclear ones like this one pictured below.