Yongbyon Nuclear Scientific Research Center: Expansion Work Continues

Commercial satellite imagery of the Yongbyon Nuclear Scientific Research Center indicates that expansion and refurbishment work continues throughout the site, reinforcing the notion that Kim Jong Un’s call “to expand the production of weapon-grade materials needed for an ‘exponential’ increase in the country’s arsenal” was not an idle request.

Major activity has been observed throughout the site, especially around the Experimental Light Water Reactor (ELWR), the 5 MWe Reactor, and within the uranium conversion area. Further, improvements to the Kuryong River causeway channel dam and other new building construction projects throughout the complex demonstrate significant investment in improving the various components of the country’s fissile material production capabilities.

Figure 1. Overview of Yongbyon Nuclear Research Center. Image Pleiades NEO © Airbus DS 2023. For media options, please contact [email protected].


Water discharge south of the ELWR pump house, which has been noted in previous reports, continues, indicating testing or cooling operations are still underway.

Construction also continues on a building first observed on March 17 continues north of the engineering building. While the exact number of floors it will have upon completion is unclear, its foundation footprint is equal to that of the original engineering building. This is the second building to be constructed adjacent to the engineering building; work was completed on the other, a one-story structure perpendicular to the engineering building in November 2022. Additional materials, a mobile crane and possible footers have been brought in for what appears to be yet another structure.

Placed along the access road separating the engineering building from the ELWR are at least 20 probable canisters, as well some longer, cylindrical objects (these may also be additional canisters just placed end-to-end). In front of the engineering building, new materials have been placed in the parking lot. The exact purpose of these materials is unclear, although they may be related to the ongoing construction or maintenance activity at the ELWR.

Figure 2. Close up of reactor area. Image Pleiades NEO © Airbus DS 2023. For media options, please contact [email protected].

5 MWe Reactor

After an almost continuous discharge of cooling water into the Kuryong River since July 2021, this activity ceased between March 21 and April 1. On imagery from April 12, the discharge had resumed, but on imagery from April 20 it had stopped again (Figure 2). Separate analysis of the activity at Yongbyon’s 5 MWe can be found here.

Figure 3. Close up of 5 MWe Reactor area.  Image Pleiades NEO © Airbus DS 2023. For media options, please contact [email protected].

Uranium Conversion Area

Significant new construction work is ongoing throughout the Uranium Conversion Area, where the Uranium Enrichment Plant (UEP or former Fuel Rod Fabrication Plant) and related facilities are located. Highlighted in our previous report, three new buildings are under construction in the southern part of the complex. While their purpose remains unclear, it appears two of the buildings will be at least two-story structures.

As construction continues at the UO2-UF4 buildings, evidenced by an active tower crane and materials scattered around the buildings, little change is observed to the exteriors, suggesting most of the work is occurring inside.

Since March 21, at the Yellowcake-UO2 conversion building, over 30 canisters or drums and other material have been removed from within the building, suggesting renovations are likely taking place inside. Around the UEP, similar canisters can be seen outside buildings, likely indicating that interior work may also be occurring elsewhere within the complex.

Figure 4. Construction activity continues throughout UEP Complex. Image Pleiades NEO © Airbus DS 2023. For media options, please contact [email protected].

Other Activity

Construction and refurbishment of the dam, located west of the Radiochemical Laboratory (RCL) complex, is in full swing. The causeway crosses the three-channel island previously constructed to manage the flow of the Kuryong River during both the wet and dry seasons, and the dam services an adjacent pump house to ensure a constant source of water for the UEP and RCL. Pile post shadows are visible along the dam, indicating attempts to better stabilize it to hold its earthen fill. This activity is part of a decades long effort to manage the river flow and ensure adequate water supply for the center as a whole. The east channel has been blocked to allow for dam reconstruction, and dredging work is visible along the opposite bank. Work for the placement cisterns along the riverbank continues.

Figure 5. Close up of dam refurbishment west of RCL complex. Image Pleiades NEO © Airbus DS 2023. For media options, please contact [email protected].
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