North Korea operates a critical uranium refining facility in North Hwanghae province’s Pyongsan county that serves as a critical link in its nuclear weapons chain. The plant converts mined uranium ore into yellowcake concentrate—essentially purified uranium ready for the next stage of weapons production. This yellowcake then travels to the Yongbyon Nuclear Complex, among other facilities, where scientists enrich it to the high levels needed for nuclear bombs.
Waste generated at the Pyongsan uranium facility has historically been sent to a reservoir across the river for sedimentation. However, satellite imagery has captured evidence that as the sedimentation pond reached capacity, North Korea began discharging wastewater directly into the river system.
My satellite analysis utilized WorldView-3 imagery available through the World Imagery Wayback service provided by the Environmental Systems Research Institute (ESRI) in the United States to examine the wastewater discharge situation. Wastewater released from the sedimentation pond flows downstream along waterways, eventually joining the Yesong River and flowing south through Ganghwa Bay before entering the West Sea. This raises serious concerns about contamination of South Korean rivers and coastal waters.
High-resolution satellite imagery (60 centimeter resolution) captured in late October last year shows wastewater from the Pyongsan uranium facility’s sedimentation pond being discharged through drainage channels into a small stream. This stream flows two kilometers before joining the Yesong River, which then flows south to meet waters from the Han River, passes through Ganghwa Bay, and eventually reaches the West Sea.
As visible in the upper left of the satellite image, the Pyongsan uranium facility has historically sent waste through pipelines to the reservoir for sedimentation. As solid waste accumulated in the reservoir, black sludge formed and built up from the bottom, rising to the water surface level. The wastewater appeared ready to overflow beyond the sedimentation pond. Satellite imagery has captured North Korea neglecting the sedimentation facility and discharging untreated wastewater directly into the river system.
High-resolution satellite imagery shows that North Korea excavated an underground tunnel connecting the external drainage system to the sedimentation pond, creating a discharge pathway for wastewater. The leachate flowing from the sedimentation pond through the drainage channels appears as dark coloration in the imagery. This constitutes unauthorized discharge of uranium concentrate waste beyond the sedimentation facility.
Construction of this drainage system was first identified by Jacob Bogle, a U.S. civilian satellite imagery expert, who published details of the mysterious excavation work on his website (AccessDPRK) on January 5, 2023. Satellite imagery indicates the drainage construction began around March 2022, in early spring. I also confirmed and analyzed the drainage construction situation in detail on June 22, 2024. The late October satellite imagery shows the drainage system connected to the sedimentation pond through underground tunnels, with leachate confirmed flowing along the small stream.
Across the river from the Pyongsan uranium facility lies a large reservoir with a surface area measured at 34 hectares. Satellite imagery indicates that as North Korea has continued nuclear material production activities, waste has accumulated in the sedimentation pond to saturation levels. Chronological satellite imagery shows that sludge covered only 1.9 hectares in 2006, expanded to 7.5 hectares by 2018, and significantly increased to 16.6 hectares by October 2024. The accumulation of solid waste sludge and surrounding wastewater spread has substantially increased the sedimentation pond’s surface area. The pond has become severely contaminated, turning green with visible algae blooms. The toxic, noxious odors likely permeate the surrounding area.
Several years ago, North Korea-focused internet outlets 38 North and Radio Free Asia (RFA) raised concerns that wastewater from the Pyongsan uranium facility was leaking into the Yesong River, potentially contaminating South Korea’s Han River estuary and West Sea with radioactive waste. As domestic media coverage heightened awareness of the situation’s severity, South Korea’s Ministry of Unification collected samples from the Han River and West Sea for water quality analysis by testing agencies and publicly announced the results. The ministry’s October 21, 2019 announcement concluded there were “no unusual findings in Han River and West Sea samples, and no highly radioactive contaminants exist at the Pyongsan uranium refining facility.”
However, the current situation differs significantly from the past. Previously, the concern involved aging pipelines leaking waste into the Yesong River. Since then, pipeline repairs or replacements appear to have addressed the leakage situation, as no such leaks are visible in satellite imagery.
Now, satellite imagery reveals North Korea’s intentional discharge of sedimentation pond wastewater into waterways. North Korea completed drainage construction in the latter half of 2024, and high-resolution satellite imagery has captured full-scale wastewater discharge from the Pyongsan uranium facility’s sedimentation pond. Despite knowing that the international community monitors North Korea’s key facilities closely through satellite surveillance, North Korea has proceeded with unauthorized waste discharge. North Korea appears to show no consideration for its neighbors. The contaminated Yesong River water now flows south through Ganghwa Bay and Gyeonggi Bay before ultimately reaching the West Sea. Verification efforts appear necessary.
