Russia may have supplied North Korea nuclear reactor for submarine

South Korea’s military has obtained intelligence suggesting that Russia supplied North Korea with a nuclear reactor for use in nuclear-powered submarines, and is currently working to verify the report. If confirmed, the action will have major repercussions for Seoul-Moscow relations as well as the global security order.

Russia is believed to have handed over two to three nuclear submarine modules to North Korea in the first half of this year, according to multiple government officials on September 16.

These modules include the reactor, turbine and cooling system — the core components of a nuclear propulsion unit. This raises the possibility that North Korea received an entire propulsion system, including a functioning reactor. The modules were reportedly not newly manufactured but taken from decommissioned Russian submarines.

“Since last year, North Korea has been persistently requesting nuclear submarine technology and advanced fighter jets from Russia,” said one government source, speaking on condition of anonymity. “Russia was initially reluctant but appears to have agreed to provide them this year.”

North Korea has been pursuing nuclear submarine construction as a national priority, regarding the possession of strategic nuclear submarines capable of striking the United States as the completion of its nuclear force.

On March 8, the North’s state-run Rodong Sinmun published photographs of its leader Kim Jong-un inspecting what appeared to be a nuclear-powered strategic missile submarine under construction.

Experts have long argued that North Korea lacks the technical capability to build a nuclear submarine quickly, especially since a submarine reactor is its most critical component. Until now, North Korea has been unable to produce small-scale reactors suitable for submarine use. That assessment could change if the country has acquired Russian modules.

By obtaining them, North Korea would gain access to reactor technology it has never been able to develop on its own. Pyongyang had pressed Moscow for such technology in return for sending personnel to support Russia’s war effort in Ukraine.

“North Korea could reverse-engineer the Russian reactor, running it on land to gain practical knowledge,” said Lee Chun-geun, an emeritus research fellow at the Science and Technology Policy Institute.

If Russia did transfer these modules, it would mean Moscow has crossed a “red line,” fundamentally undermining the Nuclear Nonproliferation Treaty (NPT). Such a move would almost certainly trigger additional international sanctions against both North Korea and Russia.

The intelligence obtained by South Korea has reportedly been shared with the United States and allied nations.

Still, some officials urged caution.

“We are considering several possibilities and assessing the credibility of the intelligence,” one government source said.

In response to an inquiry from Rep. Kang Dae-sik of the People Power Party, the Defense Intelligence Agency said, “The recent strengthening of military cooperation between Russia and North Korea could lead to the transfer of nuclear submarine reactor technology. We are closely monitoring related developments.”

BY LEE CHUL-JAE [lim.jeongwon@joongang.co.kr]