Is Russian technology behind North Korea’s new nuclear submarine?

SEOUL – A major question is emerging over North Korea’s unveiling of what it claims to be an 8,700-ton nuclear-powered strategic guided-missile submarine – whether Russia has assisted Pyongyang in securing the naval reactor technology that would make such a leap possible.

The submarine under construction, revealed during

North Korean leader Kim Jong Un’s on-site inspection

and reported by the North’s state media, the Korean Central News Agency (KCNA), on Dec 25, is significantly larger than the US Navy’s Virginia-class nuclear attack submarine.

KCNA said it represents an “epoch-making” upgrade in the North’s nuclear war deterrent. Mr Kim reiterated that the ongoing development of the nuclear-armed fleet would serve as a “reliable shield” against perceived threats from the US-South Korea alliance.

With the rapid timeline and scale of progress Pyongyang claims, analysts in Seoul say suspicions of Russian assistance are difficult to dismiss.

“North Korea’s nuclear submarine development had long seen little visible progress, but suddenly a nearly completed platform appears,” said Mr Shin Jong-woo, a senior analyst at the Korea Defence and Security Forum in Seoul. “This strongly suggests the possibility of Russian support.”

The South Korean military previously warned that strengthening Russia-North Korea military ties – driven by Pyongyang’s supply of munitions and troops to Russia for its war in Ukraine – could expand into naval reactor technology transfers, a step that would have far-reaching implications for North-east Asian security.

Professor at the University of North Korean Studies Yang Moo-jin said that the submarine programme fits into a broader pattern of military cooperation between Moscow and Pyongyang.

“North Korea has been developing and test-launching new missile systems based on Russian technologies, and naval modernisation has become a central part of Kim Jong Un’s strategy to extend nuclear armaments to the navy,” he said.

“Even if Russia does not supply a complete reactor, targeted support could accelerate progress in submarine deployment and advanced weapons testing.”

Yet experts are far from unified.

Mr Choi Il, director of the Submarine Research Institute and a retired Navy captain, pushed back on speculation that a Russian reactor may have been installed outright.

“Technically, mounting a secondhand Russian reactor into a new North Korean hull is almost impossible,” he said.

“Politically as well, Moscow is not in a position to openly back North Korea’s construction of a ballistic missile submarine.”

Mr Choi added that the design and construction likely began before Russia invaded Ukraine, making it inconsistent with the theory that Pyongyang received a reactor as compensation for wartime support.

Still, he did not rule out more limited involvement.

“Russia may have provided technical know-how or expert manpower,” he said, “but the reactor itself should be viewed as a North Korean product”.

Despite Pyongyang’s show of progress, questions persist over whether the submarine is genuinely near deployment. The vessel has not yet undergone a formal launch ceremony, and no independent confirmation exists that internal combat systems and a functioning reactor are installed.

Mr Choi described the submarine’s presentation as theatre more than readiness.

“North Korea remains focused on demonstration effects,” he said. “There is no indication this submarine is close to operational deployment.”

Other analysts echoed that assessment, saying the roll-out may be timed to fulfil political goals, such as meeting milestones in Pyongyang’s five-year defence plan.

Professor at Kyungnam University’s Institute for Far Eastern Studies Im Eul-chul said that the key challenge is safely miniaturising a naval reactor – expertise that even advanced nuclear navies take decades to master.

“Securing reactor stability is the decisive hurdle,” he said. “How fast Russian assistance is provided – and at what scale – will determine when the submarine can truly enter service.”

Meanwhile, Mr Kim Jong Un has accused Seoul’s own exploration of nuclear-powered submarine capabilities of “worsening instability” and vowed to accelerate naval nuclear weaponisation in return.

South Korea’s defence authorities warn that Pyongyang’s growing military alignment with Moscow – underscored by its

deployment of an estimated 15,000 North Korean troops to Russia

since late 2024 – could lead to expanded technology transfers in return.

Officials in Seoul believe North Korea may be seeking Russian assistance on intercontinental ballistic missiles and nuclear-propelled submarine technology, raising concerns that the wartime partnership could directly accelerate the North’s strategic weapons programmes. THE KOREA HERALD/ASIA NEWS NETWORK