North Korea’s Yongbyon Complex: Activity Picks Up

Commercial satellite imagery of the Yongbyon Nuclear Scientific Research Center from October 27 indicates activity has picked up throughout the complex. While previously reported construction and flood-damage repair work continues, smoke or vapor is observed emanating from a building just south of the UEP (Uranium Enrichment Plant). Historically, this building was used to recover and purify uranium from yellowcake and, in some cases, from leaching solutions from uranium milling facilities. However, what is taking place now is unclear.**

Uranium Enrichment Plant Complex

At the UEP complex, there appears to be smoke or vapor emanating from the UO2 Production Process Building south of the UEP, which historically housed the refractory furnaces used to produce uranium dioxide (UO2) from ammonium diuranate. Production of UO2 is one of the steps in producing UF6, which is then fed into the Uranium Enrichment Plant. This activity is consistent with observations reported in the IAEA’s most recent report. Whether these emissions are indications of UO2 production or some other operation is unclear.

Additionally, three specialized railcars are parked at the rail spur at the east end of the UEP complex. In recent years, they have appeared at this rail spur occasionally, about three or four times a year, staying for some seven to ten days at a time. Their purpose remains unclear, but their configuration has been consistent throughout this period.

Figure 1. Smoke or vapor plume observed over facility at the UEP complex.

Reactor Area

Repair work continues at the cooling water reservoir overflow dam in the Kuryong River. Imagery from October 27 shows the dike-like structure is complete and the water levels have risen to cover the intake cisterns for the reactors. Additionally, steel trench sheeting has been installed along the dam breach, forming a solid steel wall capable of stabilizing the earthen fill that forms the bulk of the dam.

Figure 2. Repair work continues at the overflow dam.

Figure 3. Example of steel trench sheeting.

Other Activity

At the rail spur servicing the Radioisotope Production Plant, three specialized railcars are once again present. These railcars have been periodically observed in this location over the past few years.

Figure 4. Specialized railcars near Radioisotope Production Plant.

At the Main Research and Administrative Headquarters Area, construction on the unidentified building continues. Foundation work is now visible expanding in two directions from the original building, a larger expansion than previously reported.

Figure 5. Construction continues at the Main Research and Administrative Headquarters Area.

Work also progresses at the bridge-causeway area west of the UEP, where there are two man-made islands. The banks of the larger island appear to be higher and its interior continues to be filled. The purpose of this island is probably to narrow the river at this naturally wide and shallow bend, thus ensuring a constant flow of water is directed to the pump house and dam located at the riverbank nearest to the UEP and radiochemical facilities. The filling in and raising of these man-made islands may be to ensure they are not washed away during the flood season.

Figure 6. In-fill work continues within the causeway area involving a dredge and temporary rechanneling of the river.

** This report was updated shortly after publication after receiving additional information about activity at this building. This includes previous instances of emissions coming from the UO2 Production Process Building captured in imagery. Thanks to Jamie Withorne for the note https://twitter.com/jamiewithorne/status/1322260232228261888.