IAEA Warns of Expanded North Korean Uranium Enrichment at Yongbyon and Kangson

New facilities point to a growing nuclear production network

North Korea has built a uranium enrichment facility with two storeys at its Yongbyon nuclear complex that could accommodate as many as 28 centrifuge cascades, according to the International Atomic Energy Agency. The agency has also found signs that an expanded annex at Kangson, near Pyongyang, began operating in January 2026.

The findings, based on satellite imagery and photographs released by North Korean state media, point to an increase in the country's ability to produce highly enriched uranium at more than one location. The new Yongbyon building is believed to be the complex's second uranium enrichment facility. Its potential capacity could support the production of roughly 85 kilograms of uranium suitable for weapons each year, according to a study cited in assessments of the expansion.

That estimate would translate into enough material for approximately three or four additional nuclear warheads annually. The actual output depends on the equipment installed, its performance and how often it operates. The IAEA has described the new facility as a cause for serious concern.

IAEA Director General Rafael Grossi said the continued operation and expansion of North Korea's enrichment facilities violated United Nations Security Council resolutions. North Korean leader Kim Jong Un continues to present nuclear weapons as central to the country's security policy and national identity, while maintaining that Pyongyang will not give them up.

As of September 9, 2026, the central concern is the growth of the infrastructure behind the arsenal. More production sites give North Korea greater flexibility to expand its stockpile and make it harder for outside governments to monitor or restrain the programme.

What changed at Yongbyon?

Yongbyon is North Korea's best known nuclear complex and has long been associated with producing both plutonium and enriched uranium. Both materials can be used in nuclear weapons, although they are produced through different processes.

Construction of the newly identified enrichment building began in December 2024. The IAEA assessment says external work was completed several months later, followed by the installation of electrical equipment, emergency generators and cooling systems. Satellite images showed at least one cooling unit operating earlier in 2026.

Photographs from Kim's visit on June 3 showed centrifuge cascades on both floors. The agency compared those images with commercial satellite photographs taken during construction to identify the building's location and likely purpose.

A centrifuge separates different forms of uranium, increasing the concentration of the isotope needed for weapons production. A cascade is a group of centrifuges connected in stages so that the uranium becomes more concentrated as it passes through the system.

The main developments unfolded over several dates:

• In 2024, an annex was built beside the existing enrichment facility at Kangson.
• In December 2024, construction began on the new Yongbyon enrichment building.
• In January 2026, the IAEA identified signs that operations had begun in the Kangson annex.
• Earlier in 2026, satellite imagery showed at least one cooling unit operating at the new Yongbyon building.
• On June 3, photographs of Kim's visit showed centrifuge cascades installed on both floors of the Yongbyon facility.

The IAEA cannot verify the number of centrifuges installed, their efficiency or whether every cascade is running. Its estimate of 28 cascades describes how much equipment the building could accommodate. Production calculations depend on how much of that capacity is installed and operating.

How much more uranium could be produced?

A study cited in assessments of the expansion estimates that 28 cascades could contain about 4,592 centrifuges. If those machines operated at expected levels, the new facility could produce roughly 85 kilograms of weapons grade highly enriched uranium annually.

Using an estimate of about 20 kilograms of highly enriched uranium for each warhead, that amount could support approximately three or four additional weapons a year. Weapons grade uranium is uranium enriched to a concentration suitable for use in a nuclear weapon.

The calculation depends on several practical details: the design and performance of the centrifuges, the quality of the uranium fed into them, the operating schedule and the amount of material required for each weapon. North Korea restricts access to its facilities and conceals much of its nuclear infrastructure, leaving those details difficult to verify.

Other estimates put the country's existing annual highly enriched uranium output at roughly 215 to 232 kilograms. Adding the new facility's estimated 85 kilograms would bring that range to about 300 to 317 kilograms. North Korea's annual output could therefore rise above 300 kilograms if the building reaches its potential capacity.

The additional 85 kilograms would represent an increase of roughly 37 to 40 percent compared with the estimated existing output of 215 to 232 kilograms. That comparison shows the possible scale of the expansion, while the actual production rate remains uncertain.

More enrichment capacity also gives Pyongyang options beyond adding warheads. It can help maintain an existing arsenal, replace material used in weapons and expand the stockpile without depending on a single production site.

Kangson adds another production concern

Kangson, an enrichment complex near the North Korean capital, has also expanded. An annex was built beside the existing facility in 2024, and the IAEA found signs that operations began there in January 2026.

The agency could not determine whether highly enriched uranium was being produced inside the annex. North Korea has described the site as a base for producing weapons grade nuclear material, and the IAEA said the possibility of such production could not be excluded.

Satellite observations also indicated that the original uranium enrichment facility at Yongbyon remained active during the reporting period. The agency found signs that the reprocessing of spent nuclear fuel to extract plutonium may have been completed as well. Reprocessing recovers plutonium from fuel that has already been used in a reactor, providing another route to material for nuclear weapons.

Facilities spread across different locations can reduce the effect of a disruption at any one site. They also make it harder for foreign governments to build a complete picture of how much nuclear material North Korea produces.

Edward Howell, an Oxford lecturer, described concealed facilities as a central concern in assessing the programme:

What makes North Korea's nuclear programme so concerning is that many of its facilities are unknown, concealed, and thus difficult to target.

Howell also pointed to sites beyond Yongbyon, including Kangson, and said North Korea's nuclear doctrine is closely connected to both its foreign and domestic policies. His assessment reflects the difficulty facing governments that rely on remote observation instead of direct inspections.

What can the IAEA see from outside?

IAEA inspectors have been absent from North Korea since Pyongyang expelled them in 2009. The agency now relies on satellite imagery, publicly available information and photographs released by North Korean authorities.

Those methods can reveal construction, changes to buildings, vehicle movements, power use and cooling activity. At Yongbyon, comparing photographs from Kim's visit with satellite images helped the agency connect equipment visible inside the building to a location observed during construction.

Physical inspections would provide greater certainty about what is happening inside. From outside North Korea, the agency cannot verify the exact number of machines, their technical specifications, their operating rate or the amount of enriched uranium produced.

The IAEA also cannot inspect storage areas or confirm whether nuclear material has been transferred elsewhere. North Korea's closed political system and record of hiding nuclear facilities make it difficult to account independently for all nuclear material or establish the full size of the arsenal.

Public estimates consequently use ranges rather than precise counts. Assessments generally suggest that North Korea possesses dozens of warheads, while estimates of annual production vary widely. Construction and operating activity help show the direction of the programme, but the country's restrictions leave major gaps in the accounting of equipment, material and weapons.

Kim's nuclear policy and the dispute over international rules

Kim Jong Un has overseen a large number of missile tests and repeatedly called for a stronger nuclear force. North Korea has tested intercontinental ballistic missiles since 2017, developing a potential delivery system designed to reach targets far beyond the Korean Peninsula.

Pyongyang has conducted six nuclear weapons tests. The most recent took place in September 2017. In 2022, North Korea declared itself a nuclear weapons state and said that status was irreversible. It has also stated that it will not surrender its nuclear weapons.

North Korean officials reject the IAEA's authority. In a statement, the country's mission to the United Nations in Vienna argued that the agency had no legal right to interfere in the internal affairs of a nuclear weapons state outside the Non Proliferation Treaty. North Korea withdrew from that treaty in 2003 after years of disputes with the United States and international inspectors.

The IAEA and the United Nations do not accept Pyongyang's position as a basis for ignoring Security Council resolutions. Those resolutions prohibit North Korea from conducting nuclear tests and developing technology related to nuclear weapons, including uranium enrichment and ballistic missile programmes.

Grossi's warning places the latest construction within that continuing dispute. North Korea treats its nuclear force as a permanent part of national security, while the agency regards the operation and expansion of the facilities as continuing violations of Security Council resolutions.

Why sanctions have not stopped the building work

North Korea faces extensive international sanctions covering its nuclear and missile programmes. The measures restrict trade, financial activity, technology transfers and access to equipment that could support weapons production. They have raised the cost of the programme without stopping construction or research inside the country.

Centrifuge components are relatively compact and can be difficult to track. They may be produced or assembled through concealed networks, while buildings housing equipment can be presented as civilian industrial facilities.

North Korea's ability to construct new sites while limiting outside access shows why sanctions enforcement depends on intelligence sharing, inspections and cooperation among neighbouring countries. Identifying a building is only one part of the task; governments also need information about equipment and the networks supplying it.

A 2022 estimate from a research group focused on nuclear non proliferation put North Korea's annual spending on its nuclear arsenal at about $640 million. The precise figure is difficult to verify, but it illustrates the resources Pyongyang continues to direct toward weapons development despite severe economic challenges.

South Korea, Japan and the United States must take a potentially larger stockpile into account in military planning and diplomatic calculations. An expanding arsenal may also increase the risk of miscalculation during a crisis, particularly when missile tests, military exercises and political tensions occur at the same time.

Seoul proposes talks and a possible production freeze

South Korean President Lee Jae Myung proposed talks with North Korea in August 2026 on formally ending the war between the two countries. The Korean War ended in 1953 with an armistice rather than a peace treaty, leaving the two sides technically at war.

Lee said discussions about a formal end to the conflict could also address ways to halt the advancement of North Korea's nuclear capabilities. Pyongyang had not responded to the proposal as of September 9. North Korea has previously rejected negotiations when it believed their purpose was to force it to abandon its arsenal.

Lee has also said he would support an agreement between Kim and US President Donald Trump that froze North Korea's nuclear production. A freeze would stop further production under agreed terms rather than remove all existing weapons. It could limit the arsenal's growth if inspectors were allowed to verify compliance.

The new Yongbyon building and expanded Kangson facility make the scope of such an agreement more difficult to negotiate. Talks would need to address which facilities were included, how existing nuclear material would be counted and whether undeclared sites could be found and monitored.

Verification would be central to making a freeze effective. The IAEA's current dependence on remote observation leaves it without the access needed to inspect equipment, measure production or track stored material directly.

What the expansion means now

North Korea continues to invest in infrastructure that can increase its nuclear arsenal. The combination of a new enrichment building, an expanded annex, activity at the original Yongbyon facility and possible completion of plutonium reprocessing points to work across several parts of the production network.

Without inspectors on the ground, outside governments may discover expansion only after buildings are complete and equipment is installed. Grossi's warning reflects that monitoring problem as well as the continued violations of Security Council resolutions.

Kim's decision to display parts of the Yongbyon facility may have served several purposes: demonstrating technical progress to domestic audiences, signalling strength to foreign governments and supporting his claim that North Korea can expand its nuclear forces despite sanctions.

The same photographs gave analysts evidence that would otherwise have been unavailable. Images intended to display progress also helped the IAEA identify the building and assess the equipment it could contain.

The agency is expected to keep North Korea on the agenda at its General Conference in Vienna. Its assessments cannot halt construction, but they create a public record of activity and help governments judge the scale and direction of Pyongyang's programme.

The Bottom Line

• North Korea has built a uranium enrichment facility with two storeys at Yongbyon that could accommodate up to 28 centrifuge cascades.
• A study estimates that the facility could contain about 4,592 centrifuges and produce roughly 85 kilograms of weapons grade uranium annually, enough for approximately three or four warheads.
• Adding that potential output to existing estimates of 215 to 232 kilograms would bring annual production to about 300 to 317 kilograms.
• The IAEA found signs that the expanded Kangson annex began operating in January 2026, while the original Yongbyon enrichment facility remained active.
• IAEA inspectors have been absent since 2009, leaving the agency dependent on satellite imagery and public information.
• Grossi says the expansion violates Security Council resolutions. North Korea maintains that its nuclear weapons status is irreversible.
• Lee Jae Myung has proposed talks on formally ending the Korean War and supports a possible agreement to freeze nuclear production. Pyongyang had not responded to his talks proposal as of September 9, 2026.