Last September, North Korean leader Kim Jong Un declared that the North needed to “strengthen its nuclear arsenal” during a surprise visit to a previously unknown facility that produces highly enriched uranium. Kim’s visit sparked concerns and intense international interest in the facility.
With reports emerging that North Korea is focused on producing weapons-grade fissile material, recent satellite images show that fissile material is being produced at the Yongbyon nuclear complex and that facilities there are being upgraded.
Cooling water from the old nuclear reactor and the light water reactor is clearly being discharged into the Kuryong River, and thermal imagery detects high energy levels from facilities producing fissile materials, indicating intense activity is underway. Additionally, a large structure under construction at the Yongbyon complex will likely be used for uranium enrichment, and there are signs that the unfinished 50MW reactor is being dismantled.
The operational status of the old reactor and light water reactor at the Yongbyon nuclear complex in North Pyongan province is typically determined by whether cooling water is being discharged. When nuclear fuel undergoes fission in the reactor, water from the Kuryong River is brought into the facility to dissipate heat and then pumped back into the river.
The cooling water pumped from the reactor can be identified by white foam on the riverbanks. This foam is quite small and only visible when satellite images are enlarged.
Two pump stations sit on the riverbanks, one at each reactor. Spent nuclear fuel is stored on-site before being moved to a radiochemical laboratory 19 kilometers away for reprocessing, which is necessary for extracting plutonium.
High-resolution satellite images taken in early June show white foam from cooling water flowing from both pump stations into the Kuryong River, indicating that both reactors are operational.
Thermal images taken by the US Landsat 9 earth observation satellite in mid-July were used to examine the Yongbyon nuclear complex. Analysis found an average surface temperature of 24 degrees for the day, ranging from 18 to 31 degrees.
The radiochemical laboratory and the uranium enrichment facility were both emitting high heat levels (30 degrees and above, marked in red and reddish-brown in the image), indicating that both facilities are actively producing fissile materials (plutonium and highly enriched uranium).
The image shows the coal plant that powers the radiochemical laboratory in light purple and the 25MW experimental light water reactor in purple (27 degrees), which suggests that both facilities are operational.
The 25MW experimental light water reactor was built in the 2010s and began operating in October 2023, producing five times as much electricity as the original 5MW reactor. The 5MW reactor, built in the mid-1980s, is old and deteriorating, and operations there are believed to be inconsistent and inefficient.
A new building has been constructed between the radiochemical laboratory and the unfinished 50MW reactor. Measuring 122 meters by 50 meters, this large building is about the size of a soccer field. The building’s exterior is complete, but the interior condition and the building’s purpose remain unconfirmed. A perimeter wall and auxiliary structures are still under construction.
Given the new building’s similarities to the Kangson uranium processing facility in Nampo city, Rafael Mariano Grossi, director general of the International Atomic Energy Agency (IAEA), believes that North Korea may be building another uranium processing facility at Yongbyon.
About 400 meters north of the blue building sits an old 50MW reactor that North Korea never completed. Recent imagery suggests this unfinished reactor is being demolished.
North Korea started building the 50MW reactor in the mid-1980s but halted construction in 1994 after reaching an agreement with the US in Geneva that banned nuclear proliferation and called for denuclearization.
Some structures and auxiliary facilities have been dismantled since 2021, but full-scale demolition was only observed in recent satellite images.
North Korea’s demolition of the unfinished 50MW reactor appears designed either to recover and recycle some of the disassembled materials or to convert the area for another purpose. To determine North Korea’s intentions and the exact use of the new facility, continued monitoring of facility construction and reactor dismantlement using satellite imagery will be necessary.
The Korea Institute for Defense Analyses (KIDA) estimates that North Korea had 80–90 nuclear devices as of 2023 and will have a yearly production capacity of 17 devices by 2040.
