At North Korea’s Yongbyon nuclear complex, increased activity seen in satellite images indicates that Pyongyang is increasing its capacity to produce nuclear weapons, experts told Radio Free Asia.
Images show new buildings and plumes of steam in previously inactive areas of the complex, located about 90 kilometers (56 miles) north of the capital.
North Korea has long claimed that Yongbyon serves civilian and peaceful energy purposes, but the international community and monitoring organizations say the complex produces fissile material to make nuclear weapons.
The increased activity seen in April follows Kim Jong Un’s announcement at the ninth congress of the ruling Korean Workers’ Party in February that the country would strengthen and diversify its nuclear arsenal over the next five years.
Where there is smoke…
Images captured by Planet Labs on April 18 and 20 show steam emitted from the radiochemical laboratory’s thermal power plant. On March 12 and April 25, footage showed the reactor spilling water into the nearby Kuryong River. These releases are consistent with numerous other images captured since January.
Evidence suggests that North Korea is producing weapons-grade plutonium, Olli Heinonen, former deputy director general of the International Atomic Energy Agency and a distinguished scholar at the Stimson Center, told RFA.
“It appears that North Korea continues to produce plutonium in its 5-megawatt reactor and does so on a field basis,” he said, using a technical term for a production cycle from start to finish. “So it runs for about a year and then they unload the fuel, which is a very quick operation.”
Jacob Bogle, a private U.S.-based satellite imaging analyst, told RFA that as of October 2024, the complex is in its seventh cycle of irradiation and fuel reprocessing for plutonium production.
“This multi-year cycle of activity has continued to the present and is supported by two key pieces of visual evidence: a constant release of water from the 5 MW reactor throughout 2026 and occasional activity at the radiochemistry laboratory, as indicated by steam production,” he said.
These findings are consistent with confirmation from the International Atomic Energy Agency, or IAEA, that North Korea has significantly expanded its nuclear activities at Yongbyon.
During a visit to South Korea on April 15, IAEA Director General Rafael Grossi told reporters that many of Yongbyon’s facilities, including the main reactor, were active.
“This suggests a serious increase in North Korea’s nuclear weapons production capacity, which appears sufficient to produce dozens of warheads,” Grossi said, adding that the construction of a new nuclear enrichment facility comparable to existing ones had also been confirmed.
Construction in progress
Satellite imagery also confirms that new buildings are appearing in the complex. Exterior construction of one of the new buildings – believed to be a new uranium enrichment facility – was completed in November or December last year.
Bogle said melting snow on the building’s roof was visible, suggesting the building is connected to electricity and interior construction work is at a minimum still underway.
A vehicle was observed next to the building on April 15, but no external indicators have emerged to determine whether interior work is still underway or whether the facility has become operational.
Additionally, in March, the roofs of two radiochemical laboratory buildings were replaced.
New high-rise residential buildings were also constructed in the area, likely needed to house an increased workforce.
Heinonen said satellite images showed changes in the complex that are not yet understood. In the southern part of the complex, where the fuel rods were manufactured, four completely new buildings appeared.
“Some of them also seem quite well built and one of them is even separated from the others by a fence, which tells me it’s very important,” he said. “We don’t know what it is, but I think these buildings have to do with a plan by Kim Jong Un to increase nuclear weapons production and produce nuclear materials and components for nuclear weapons. So we have to consider this change in the context of his previous and current five-year plan.”
Edited by Eugene Whong.