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North Korea Discloses Ongoing Construction of an 8,700-Ton Nuclear-Powered Strategic Submarine.
North Korean state media says Kim Jong Un inspected the construction of an 8,700-ton “nuclear-powered strategic guided missile submarine” at a domestic shipyard, releasing images of a large hull in primer. If real and fielded, a nuclear-powered missile submarine would make North Korea’s nuclear force more survivable at sea, complicating allied tracking and raising crisis stability risks around the Korean Peninsula.
On December 25, 2025, North Korean state media KCNA reported that Kim Jong Un had inspected the construction of an 8,700-ton “nuclear-powered strategic guided missile submarine” at a domestic shipyard. According to the KCNA report and the photographs released with it, the vessel is intended to serve as a strategic nuclear attack submarine within the country’s naval modernization plans. The images show a large hull on a building cradle in red anti-corrosion primer, indicating a project that has progressed beyond the conceptual stage but is still under construction. KCNA describes the submarine as nuclear-powered, though the existence and maturity of any naval reactor have not been confirmed from open sources. The appearance of such a platform is relevant because it suggests a move toward a more survivable, sea-based component of North Korea’s nuclear forces, with potential consequences for deterrence and crisis stability on the Korean Peninsula.
North Korea’s 8,700-ton submarine, described as a nuclear-powered guided missile platform, would represent a major leap in size and capability, potentially enabling longer, stealthier patrols and a more survivable sea-based nuclear force, though its propulsion and operational maturity remain uncertain (Picture Source: North Korean State Media Agency)
The submarine under construction is characterized by several distinctive external features visible in the official imagery. The most prominent is an elongated, high sail that occupies a substantial portion of the hull’s upper line and appears to incorporate at least five vertical launch tube covers; some views indicate space for a possible second row, which could bring the total to ten tubes. These tubes may be associated with the Pukguksong-XA submarine-launched ballistic missile unveiled by North Korea at the National Defense Development-2025 exhibition, although this possibility has not been officially confirmed. These hatches are broadly consistent with arrangements used for SLBMs or vertically launched cruise missiles on ballistic-missile and guided-missile submarines elsewhere, but the exact configuration and missile mix cannot yet be independently verified. A small rectangular opening on the upper part of the sail that might function as a vent or exhaust for gases generated during cold-launch procedures, though its precise purpose remains unclear.
Along the flanks, a long recessed structure is visible that resembles a conformal sonar array extending to around the mid-section of the hull, likely complementing a large cylindrical bow sonar. The bow also shows markings consistent with six horizontal torpedo tubes, providing capacity for heavyweight torpedoes and possibly anti-ship missiles. The absence of visible limber holes and the generally smooth outer surface suggest a single-hull or semi-single-hull design intended to reduce hydrodynamic drag and acoustic noise.
On top of the sail, photographs reveal several modern-looking masts, including what appears to be a non-traditional optronic periscope and integrated electronic-support and communications masts.The presence of these integrated optical and communication masts and, at the same time, the absence of a classic diesel snorkel mast that is usually seen on conventional submarines, a configuration that would be consistent with a nuclear-propelled design if such a reactor is ultimately installed.
From a developmental perspective, this project appears to build on North Korea’s earlier steps in establishing a sea-based missile capability. The design of the missile compartment recalls the plug inserted into the conventionally powered Submarine No. 841 Hero Kim Kun Ok, a converted Romeo-class hull of around 3,000 tons that added a bank of launchers behind the sail. The new 8,700-ton platform, however, seems to have been conceived as a purpose-built strategic submarine rather than a conversion, with its hull form, larger displacement, sail length and internal volume optimized around missile carriage and acoustic systems.
KCNA’s description of the vessel as a “nuclear-powered strategic guided missile submarine” suggests that Pyongyang intends it to be one of the key programs identified in its defence development plans. Some South Korean assessments further speculate that the design could be intended for a relatively small reactor using highly enriched fuel, potentially allowing long intervals between refuelling, though there is no independent evidence yet to substantiate this claim and no public indication that a naval reactor has completed testing.
If the reported nuclear propulsion is eventually realized, the submarine would offer tactical advantages that go beyond those of North Korea’s existing diesel-electric missile submarines. A naval reactor would enable sustained submerged operations without the need for frequent snorkeling, thus improving survivability against air and surface surveillance as well as anti-submarine warfare assets. A battery of five to ten SLBM or cruise-missile tubes, combined with six torpedo tubes, would give the platform the potential to conduct both strategic and conventional missions, ranging from nuclear deterrent patrols to strikes against regional targets and sea-denial operations in contested waters. The large flank sonar and bow array implied by the hull form could provide improved detection ranges against surface ships and submarines, allowing the vessel to operate as both a launch platform and a sensor node within North Korea’s maritime posture. These advantages remain prospective rather than proven at this stage and will depend on the eventual performance of the reactor, sensors and weapons integrated into the final design.
The emergence of such a submarine, even if it initially operates close to home waters, would complicate regional defence planning once it becomes operational. A sea-based nuclear force is inherently harder to locate and pre-empt than fixed land-based missile units, which means that South Korea, Japan and the United States would need to assign additional resources to continuous anti-submarine surveillance around the Korean Peninsula and, potentially, farther afield. At the same time, a single large submarine offers only a limited increase in redundancy compared with North Korea’s existing land-based missile forces; a credible sea-based deterrent would require multiple hulls, trained crews and sustained logistic support. The current project therefore represents an early step toward such a posture rather than its completion.
If completed and brought into service, such a large missile-carrying submarine would mark a major qualitative shift in North Korea’s naval capabilities. The combination of a substantial missile compartment, extensive sonar fit, six-tube torpedo armament and claimed nuclear propulsion points to an ambition to field a patrol-ready strategic asset rather than a pure test platform. Many technical questions remain open, including the maturity of the reactor, the acoustic signature of the hull and the characteristics of the missiles intended for carriage. Nevertheless, the project already indicates that North Korea is working to embed part of its nuclear capability at sea, and that regional security planning will need to take into account the possible future presence of an 8,700-ton strategic guided-missile submarine in the waters of Northeast Asia.
Written by Teoman S. Nicanci – Defense Analyst, Army Recognition Group
Teoman S. Nicanci holds degrees in Political Science, Comparative and International Politics, and International Relations and Diplomacy from leading Belgian universities, with research focused on Russian strategic behavior, defense technology, and modern warfare. He is a defense analyst at Army Recognition, specializing in the global defense industry, military armament, and emerging defense technologies.