North Korea 'Expanding' Major Nuclear Site: Ana...

By Ellie Cook

Senior Defense Reporter

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North Korea is modernizing and building out one of its main nuclear sites, according to analysts, after Pyongyang's supreme leader, Kim Jong Un, said the secretive country would bolster its nuclear forces.

Satellite imagery shows North Korea expanded construction at the Yongbyon nuclear site over the past two months, according to analysts with the 38 North project, run by the Stimson Center non-profit. The 38th parallel north has historically marked the border between North and South Korea.

Why It Matters

Defying close to two decades of United Nations sanctions on the country, North Korea has forged ahead with its ballistic missile testing, and can launch nuclear weapons using a host of different delivery systems, including intercontinental ballistic missiles able to reach the United States.

Experts say Pyongyang likely has enough highly enriched nuclear material for up to 90 nuclear bombs, and is thought to have assembled 50 nuclear weapons.

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What To Know

The sprawling Yongbyon campus, north of Pyongyang, is North Korea's only plutonium producer and a major source of other nuclear material, with the Kuryong River cutting through the site used to cool some of the facility's nuclear reactors. It hosts a 5 mega-watt power nuclear reactor, which is relatively modest, but observers say North Korea is also building an experimental light-water reactor at the site that is not yet up and running.

The 38 North analysts said a suspected uranium enrichment site at Yongbyon "has become the most active since the start of 2025."

Rafael Grossi, the head of the U.N.'s International Atomic Energy Agency (IAEA), said in June the watchdog was monitoring the construction of a new building at Yongbyon similar to an area of the Kangson enrichment plant, a separate site near Pyongyang. The existence of the Kangson facility was revealed in 2018.

Experts at the Middlebury Institute of International Studies at Monterey said earlier this year the suspected new facility at Yongbyon had a central hall surrounded by office and support areas, and would likely host centrifuges.

Construction workers had completed a roof over the suspected additional enrichment site at Yongbyon by June, and two support buildings were finished off around the facility between June and late October, the 38 North experts said in an analysis published on Friday.

Satellite imagery also shows a vehicle shed had been added and "an enclosed passageway now joins that building with the main building," the analysts said. Work is also thought to be completed on paving around the compound.

What appear to be six heat exchanges—needed to cool centrifuges—have been installed close to the main building of the suspected enrichment site since September and work has continued on a radioactive waste storage area, according to the analysis. Other changes were observed elsewhere at Yongbyon, including works to strengthen a dam at the site.

"The undeclared enrichment facilities at both Kangson and Yongbyon are of serious concern," Grossi said in June.

The IAEA chief said there was no evidence of major changes at North Korea's Punggye-ri test site in the northeast of the country, but that the area "remains prepared to support a nuclear test."

North Korea is the only country that has carried out full nuclear tests this century.

Pyongyang first started its nuclear path—with help from the then-Soviet Union—in the late 1950s, shortly after the end of the three-year Korean War. North Korea built several facilities at Yongbyon over the following years, according to U.N. experts.

The IAEA started inspecting North Korean nuclear sites in the early 1990s. It quickly said it had found inconsistencies in nuclear material declared by Pyongyang and the watchdog's own analysis, and that North Korean officials barred access to sites linked to nuclear waste.

The agency for years had turbulent relations with Pyongyang over its nuclear facilities and said it had never gained a full picture of the country's nuclear program. The U.N. Security Council has leveled sanctions at North Korea over its missile and nuclear programs since 2006.

Observers have said they believe Russia has been helping North Korea with its weapons development. Pyongyang last year sent thousands of troops to Russia's Kursk region to battle Ukrainian troops that claimed a chunk of land around the border in summer 2024.

The country's supreme leader, Kim Jong Un, said while touring one of the closed-off nation's nuclear sites in January that 2025 was a "crucial year" for the country's weapons programs and said Pyongyang would beef up its nuclear forces. He said the country's scientists and workers had achieved "remarkable successes" in producing weapons-grade nuclear materials.

Diplomatic efforts to limit North Korea's nuclear and missile programs have ebbed and flowed. A summit between Kim and U.S. President Donald Trump during his first term collapsed, and although Trump has indicated a willingness to resume dialogue with Pyongyang, North Korean officials have so far appeared tepid on a meeting and batted away fresh attempts to warm up relations from South Korea's government.

North Korea has insisted it will not denuclearize.

What People Are Saying

The 38 North analysts said in a piece published on Friday: "Yongbyon plays a critical role in the country’s production of nuclear material for its weapons program, as the sole producer of plutonium and a significant source of enriched uranium."

Kim's sister, Kim Yo Jong, a senior official in the Pyongyang regime, said in July that the “personal relationship" between Trump and Kim "is not bad."

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