North Korea’s growing nuclear capabilities have recently come back into public focus. Speaking in Seoul, International Atomic Energy Agency (IAEA) chief Rafael Grossi highlighted “very serious” advances in Pyongyang’s Yongbyon complex infrastructure, including a “probable” addition of a new uranium enrichment facility. Several sources indicate that Pyongyang is currently estimated to possess upwards of 50 nuclear warheads.
Such rapid advances in North Korea’s armament, however, come as no surprise. Under the Comprehensive Strategic Partnership with Moscow, Pyongyang has sought to utilize Russian expertise to expand its conventional arsenal with new delivery methods and launch platforms. The Korean People’s Army has also gained experience fighting in Russia and exposure to drone warfare and tactics.
Since the invasion of Ukraine, the scale of cooperation has come to mirror that of a full-fledged military alliance details about technology transfers and the full extent of cooperation remain opaque. A growing body of indicators, however, suggests that Moscow may be playing a larger role in Pyongyang’s military and nuclear modernization than previously understood, with significant implications for regional security and proliferation dynamics.
This report traces these links by triangulating advances in uranium enrichment and potential nuclear submarine propulsion systems, the intermediary networks involved, and the strategic logic behind the growing degree of Russian involvement in Pyongyang’s nuclear complex. For regimes such as North Korea, nuclear autonomy has increasingly proven to be the main component of deterrence, stability, and power projection, making Russian assistance to Pyongyang’s military and nuclear modernization particularly consequential for the security environment in the Asia-Pacific region.
Indicators of Russian Technical Transfers
One of the most significant suggestions of nuclear cooperation between Russia and North Korea centers around the possible transfer of propulsion systems for Pyongyang’s new nuclear-powered ballistic missile submarine (SSBN), capable of carrying submarine-launched ballistic missiles (SLBMs).
As some experts note, the transfer of two or three nuclear reactors by Moscow was possible, while others allude to the transfer of parts such as cooling systems or reactor cores. If successful, Moscow’s assistance to North Korea’s nuclear submarine program could shave several years off its deployment timeline, introducing new challenges for US and allied anti-submarine warfare operations in a potential dual-contingency scenario involving both the Korean Peninsula and the Taiwan Strait, albeit not dramatically.
Multiple coinciding factors indicate that such an effort was on track to take place in early December 2024, when the Russian cargo ship Ursa Major was en route from St. Petersburg to Vladivostok. The ship, however, mysteriously sank off the coast of Cartagena.
Ukraine’s Defense Intelligence reports further indicate that Ursa Major was a part of Russia’s shadow fleet under the internationally sanctioned SC-South LLC, a subsidiary of Russia’s sole provider of shipping services to the Ministry of Defense (MoD), Oboronlogistika LLC.
While no official information about the cargo has surfaced, sources indicate that the ship was transporting sensitive, military-related freight, with “undeclared heavy containers at the ship’s stern.” The presence of Russian Navy ships Ivan Gren and the oceanographic vessel Yantar at the site of Ursa Major’s sinking points to the significance of the freight.
Reactor Compatibility
Ursa Major’s port of origin aligns with the location of the St. Petersburg-based Malakhit Marine Engineering Design Bureau (SPMBM), which designed the Akula-class (Project 971 Shchuka-B) submarines, as well as the Rubin Central Design Bureau, which designed the Project 941 Typhoon nuclear-powered submarines.
North Korea’s own nuclear submarine is estimated to have a surface displacement of 8,700 tons, which makes its specifications most closely align with the Akula-class. The Akula is powered by the OK-650 (OK-9BM) series pressurized-water nuclear reactor, with an estimated capacity of 180–190 megawatts. Considering Pyongyang’s own nuclear submarine displacement and dimensions, this makes the possible transfer of complete units or parts of less powerful VM-A and VM-4 series propulsion systems, with capacities of 70–90 megawatts, less likely.
Nevertheless, based on estimated dimensions of the Russian OK-650 reactor, which are broadly comparable to those of US Navy Los Angeles-class SSNs, and in the absence of official data on the weight of the OK series, Ursa Major’s dimensions would have allowed for the possible transfer of complete reactor units from donor submarines.
H.I. Sutton provides a detailed breakdown of such prospective propulsion donors. Indeed, in recent years, Russia has decommissioned several Akula-class boats that could have been used as donors, with the latest one, Kashalot, being put out of service in 2019. Moreover, most decommissioned Akula-class boats are located at the Zvezda Shipyard near Vladivostok (Ursa Major’s port of destination) and in St. Petersburg (Ursa Major’s port of origin), although the Akula in St. Petersburg has been rumored to be converted into a museum. Other Akula-class submarines that are currently reported as not operationally ready are undergoing modernization at the Sevmash plant in Severodvinsk.
While it is too early to verify the transfer of complete reactor units, the history of the Akula-class submarines and the patterns around decommissioning indicate a potential connection that at minimum spans technological transfers or transfers of reactor parts such as cooling systems to Pyongyang. Moscow also has a history of leasing such submarines, notably to India in the 2010s, which suggests that sensitive technologies are not entirely vetoed for export to aligned countries.
In this light, it would be equally incorrect to rule out transfers of nuclear submarine parts in any capacity until further official information from defense intelligence or other highly credible sources, as well as the findings of an official investigation into Ursa Major’s cargo, become available.
Uranium Enrichment Bottlenecks
Growing Vertical and Horizontal Demand in Uranium
An emergence of a submarine-based nuclear delivery capability alone introduces a structurally significant demand for highly enriched uranium (HEU). Naval propulsion reactors, such as the Russian OK-650 or domestically developed alternatives, typically rely on HEU, often at elevated enrichment levels.
A recent RUSI report assesses that HEU in North Korea likely supports a range of warhead design applications across tactical and strategic systems, including potentially supplementing plutonium in strategic systems to extend limited fissile stocks. Pyongyang, therefore, is facing the need to sustain a more complex and resource-constrained fuel cycle in which weapons production is now potentially facing the addition of a naval propulsion program.
When combined with prospective naval propulsion requirements, this points to increasing demand in HEU, consistent with IAEA assessments of significant expansion in enrichment-related infrastructure at Yongbyon, including an unconfirmed but potentially relevant new facility construction.
Some analysts indicate that, in order to make the submarine component more viable, Pyongyang will need to maintain at least several submarines operationally ready. HEU enrichment expansion could therefore eventually support broader submarine propulsion requirements. Such developments, however, would not constitute an immediate enabler of an operational submarine fleet, but rather a longer-term supporting component of a maturing nuclear posture.
Russia’s Role in Helping with Supply Chain Constraints
Similarly, North Korea’s sources of uranium ore development, extraction, and processing remain opaque. Deeper and more diversified nuclear cooperation with Russia, while officially off the books, could be the solution to potential extraction or supply bottlenecks.
Russian state media TASS has recently stated that, under the Comprehensive Treaty, “…the countries will develop cooperation and exchanges, as well as joint research, including in the field of ‘peaceful nuclear energy.’” While the extent of the “peaceful nuclear energy” component of cooperation is not transparent, several coinciding reports indicate that such cooperation is becoming more structural, including mineral extraction, scientific research, and industrial processing that can support North Korea’s broader nuclear fuel cycle.
In August 2025, North Korean geologists underwent advanced training in geology, including uranium ore location and extraction, at Rosgeo Holding, Russia’s largest geological surveying company, and the Irkutsk National Research Technical University (INRTU).
Furthermore, INRTU and several other universities in Russia, according to the dean, are “a platform for educating students from North Korea in various fields, including geology, information technology, energy, mechanical engineering, and chemical technology.” Consequently, integration of North Korean geologists into Russia’s surveying sector indicates growing and multidimensional research ties between North Korea and Russia.
However, according to the Polish Institute of International Affairs (PISM), constraints in research cooperation could still exist.
“In light of the history of the Soviet Union and Russia’s current policies, any proliferation of blueprints for designs of modern thermonuclear weapons, constructed by the centres in Sarov (VNIIEF) and Chelyabinsk-70 (VNIITF) would be less probable, and extremely risky. Due to this, Kim’s regime might be left with a dependence on North Korean scientists and engineers, as well as making use of opportunities for broader access for North Korean students to a limited number of Russian universities and higher schools, along with espionage there.”
Considering the growing number of North Korean laborers, students, and scientists entering Russia, research cooperation between the two countries would continue to evolve both officially and through other means. Following geological training, more substantial nuclear research has the potential to become more plausible in the future.
Political Reasoning
While indicators point to deeper involvement in North Korea’s expanding nuclear complex, such a move carries political risks. The Kremlin, nevertheless, appears willing to make such a tradeoff.
Russian foreign policy has long-leveraged regional tension short of destabilization. A nuclear, Russia-leaning North Korea is Moscow’s force multiplier in the Asia-Pacific region. Considering the China-Russia partnership and Moscow’s growing dissatisfaction with Beijing’s pragmatism over its war in Ukraine, having a more pro-Russian Pyongyang gives the Kremlin leverage in its own relationship with Beijing and in Beijing’s periphery.
Similarly, a closer relationship maintains Moscow’s pipeline of troops and weapons from North Korea. Pragmatism has defined Kim Jong Un’s approach to Russia, and in the short term, this alignment appears to have benefited both regimes.
China’s MFA’s recent visit to Pyongyang may be connected to this logic and may have been conducted as an effort to counterbalance the growing influence of Moscow over Pyongyang with economic benefits and bilateral ties. As the visit was a premise to discuss different visions on certain “regional and international issues,” the visit suggests Beijing’s growing concerns over the depth of Pyongyang-Moscow cooperation. There is a common notion that Beijing has “lost control” over its neighbor. In this regard, coordinated engagement creates openings for reengagement with Pyongyang over its nuclear arsenal and Russia’s involvement in its expansion.
What Can Be Done
Beijing, like Washington, has little interest in seeing Pyongyang’s enrichment capabilities and nuclear arsenal expand unchecked. For China, a rogue, less controllable regime becomes more of a liability than an asset. With Russia’s involvement in this expansion, coordinated pressure from Washington and Beijing aimed at weakening Pyongyang’s reliance on Moscow could help reduce regional tensions.
Simultaneously, experts suggest that in the US, South Korea, and Japan, there is a growing recognition of the need to manage rather than fully eliminate North Korea’s nuclear capabilities. However, Pyongyang’s evolving relationship with Russia is one of several factors reinforcing its nuclear posture, and any future dialogue with North Korea regarding these factors that does not account for this dimension is likely to face significant constraints.
Russia has become an important enabler of North Korea’s military modernization. In this reality, an open dialogue with Pyongyang remains an option, but its prospects for meaningful progress would likely improve if external sources of military support and modernization are more effectively constrained through sanctions and pressure on Moscow. Under such conditions, prospects for greater stability on the Korean Peninsula and in the wider Asia-Pacific region may become more attainable.
