North Korea has built a new uranium enrichment facility at its Yongbyon nuclear complex capable of housing thousands of centrifuges, the UN’s nuclear watchdog has warned, describing the development as a “cause for serious concern” that shows Pyongyang continuing to expand its nuclear programme despite decades of international sanctions.
North Korea has built a new uranium enrichment facility at its main Yongbyon nuclear complex, the United Nations’ nuclear watchdog has said, describing the development as a “cause for serious concern.” The International Atomic Energy Agency (IAEA) said the two-storey building could hold up to 28 centrifuge cascades used to enrich uranium, in a report released late last month. The agency said the discovery demonstrated that North Korea continues to expand its nuclear programme, despite having been under UN Security Council sanctions since 2006, measures that have been repeatedly strengthened over the years in an effort to halt Pyongyang’s development of nuclear weapons and ballistic missiles.
How the facility was identified
The IAEA said it had been tracking the facility since construction began in late 2024, identifying it well before North Korea publicly acknowledged its existence. By 2025, analysts had already assessed the structure as highly likely to be an enrichment facility, based on its dimensions, layout and security arrangements, which closely resembled those of the known facility at Kangson.
Confirmation came after North Korean leader Kim Jong Un visited what state media described as a “newly-inaugurated nuclear materials production factory” in June this year. The IAEA said it identified the building by comparing satellite images with photographs of Kim’s visit released by North Korean state media, allowing the agency to connect the site it had been monitoring with the facility publicly shown by Pyongyang.
Scale of the potential expansion
Expert analysis suggests the new two-storey building could accommodate roughly 4,600 centrifuges arranged into 28 cascades, representing a potentially substantial expansion of North Korea’s enrichment capability. One expert assessment puts the facility’s potential output at roughly 100 to 200kg of highly enriched uranium per year, though this figure reflects estimated capacity rather than confirmed actual production.
Using the IAEA’s approximate benchmark for the amount of highly enriched uranium required to build a single nuclear weapon, this estimated capacity could theoretically represent the material for around four to eight weapons annually. However, it is important to note that the facility could also be used to produce low-enriched uranium for civilian or research reactors rather than weapons, meaning the full estimated capacity cannot automatically be attributed to warhead production.
A claimed doubling of production capacity
During his June visit, Kim was quoted by state media praising the further strengthening of the “foundation for the production of weapons-grade nuclear materials by settling the problems decisive in putting the production of nuclear materials.” He separately claimed that North Korea’s weapons-grade nuclear material production capacity had more than doubled during the 2021-2025 five-year period. Independent analysts say the newly identified Yongbyon facility provides significant physical evidence consistent with that claim, suggesting the expansion is not merely about maintaining North Korea’s existing arsenal, but substantially increasing its capacity to manufacture additional fissile material.
Expansion extends beyond Yongbyon
Concern is not limited to the new Yongbyon building alone. The IAEA has also identified continued activity at the Kangson facility, including an annex where additional centrifuges appear to have been installed. The agency has previously assessed the centrifuges at Kangson as being configured for low-enriched uranium production, though it says it cannot rule out the possibility that other cascades within the building are configured to produce highly enriched uranium instead.
Satellite observations indicate North Korea is operating several nuclear material production streams simultaneously, including uranium enrichment at both Yongbyon and Kangson, the 5 MWe reactor at Yongbyon, which produces plutonium-containing spent fuel, the radiochemical laboratory where spent fuel can be reprocessed, and the Experimental Light Water Reactor. This suggests the country’s nuclear expansion extends beyond uranium enrichment alone to include plutonium-related capabilities as well.
The IAEA continues to see indications that Yongbyon’s 5 MWe reactor remains operational, a significant detail given that spent fuel from the reactor can be reprocessed to extract plutonium for nuclear weapons. Taken together, the continued operation of the reactor and the expanding enrichment infrastructure give North Korea two distinct routes for producing fissile material.
An abandonment of denuclearisation
North Korea’s official position has hardened considerably in recent years, with Pyongyang describing its nuclear status as irreversible and explicitly rejecting the goal of denuclearisation. Following Kim’s June visit, state media said the country would continue strengthening its nuclear forces and increasing its production of fissile material. Kim had earlier described 2025 as a “crucial year” for “bolstering up the nuclear forces,” and had called for “overfulfilling the plan for producing weapons-grade nuclear materials” during a visit to the facility in January of that year.
After his June visit, Kim held a meeting specifically focused on strengthening the country’s nuclear forces, during which state media said he had “updated” figures considered critical to the country’s nuclear activities, taking into account requirements for building North Korea’s nuclear deterrent. While the exact new figure was not disclosed, analysts interpret this as potentially referring to a new target for the overall size of North Korea’s nuclear arsenal.
Current estimated arsenal
The latest expert estimates put North Korea’s currently assembled arsenal at approximately 60 nuclear warheads, though the precise number remains highly uncertain. Other estimates focus on the amount of fissile material available rather than completed warheads, meaning assessments can vary considerably depending on the methodology used. What analysts agree on is that additional enrichment capacity could allow this stockpile to grow substantially over time.
The limits of international verification
Interpreting these figures requires an important caveat: the IAEA has had no inspectors inside North Korea since 2009, meaning the agency relies heavily on commercial satellite imagery, publicly released North Korean photographs and other remote observation methods. As a result, the agency can identify construction and general activity but cannot directly verify how many centrifuges are actually operating, the enrichment level being achieved, how much highly enriched uranium North Korea currently possesses, or how much of that material has already been converted into weapons.
Analysts are similarly careful not to equate centrifuge numbers directly with the number of nuclear warheads North Korea is capable of producing, since the IAEA’s analysis of photographs from the older Yongbyon facility found that its known cascades were consistent with low-enriched uranium production, material that could be intended for the Experimental Light Water Reactor rather than nuclear weapons. Even so, having substantially more enrichment infrastructure gives North Korea greater flexibility to allocate production between reactor fuel and weapons-grade material, making the expansion strategically significant regardless of the precise amount of highly enriched uranium currently being produced.
Part of a broader military strategy
The Yongbyon expansion is consistent with the strategy set out at North Korea’s Ninth Workers’ Party Congress in February 2026, at which the country reaffirmed plans to expand its nuclear and missile forces. Analysts view the construction as part of a broader programme that includes more nuclear warheads, tactical nuclear weapons, ballistic missiles, cruise missiles and, eventually, a nuclear-powered submarine.
Sanctions unable to halt expansion
North Korea has remained under UN Security Council sanctions targeting its nuclear and ballistic missile programmes since 2006, yet the latest satellite evidence indicates that Pyongyang has continued expanding the physical infrastructure needed to manufacture fissile material. This presents a significant diplomatic challenge: while the sanctions regime has constrained North Korea in various respects, it has failed to prevent the country from expanding the core infrastructure underpinning its nuclear arsenal.
