Infrastructure Improvements at North Korea’s Yongbyon Nuclear Research Facility

A 38 North exclusive with analysis by Frank V. Pabian, Joseph S. Bermudez Jr. and Jack Liu.

Commercial satellite imagery from June 21 indicates that improvements to the infrastructure at North Korea’s Yongbyon Nuclear Scientific Research Center are continuing at a rapid pace. Modifications to the 5 MWe plutonium production reactor’s cooling system appear complete, but a less-than-normal cooling water discharge from the outfall pipe makes a determination of the reactor’s operational status difficult. The status of the Radiochemical Laboratory—used to separate plutonium from spent fuel rods—remains uncertain, although the associated Thermal Plant has likely continued operations, and a small non-industrial building of an unknown purpose has been newly erected near the cooling tower. Construction continues on support facilities throughout other operational areas of Yongbyon, especially at the Experimental Light Water Reactor (ELWR), where the new engineering office building appears externally complete and a small building similar to the one observed at the Radiochemical Laboratory has been erected.

Continued work at the Yongbyon facility should not be seen as having any relationship to North Korea’s pledge to denuclearize. The North’s nuclear cadre can be expected to proceed with business as usual until specific orders are issued from Pyongyang.

The 5 MWe Reactor

Modifications to North Korea’s 5 MWe reactor’s secondary cooling loop, which began in March, appear externally complete. A newly in-filled water channel (that includes a newly installed probable weir for controlling water flow) now leads to the pump house from the Kuryong River. (Figure 1) Determining the operational status of the reactor is particularly difficult at this time. Although a small water discharge is visible from the cooling water outfall pipe going into the river, that discharge is less than has been observed previously when the reactor was fully operational. It may simply be that this is all the water needed at this time to carry away the heat from the residual radioactivity in the reactor, if the reactor is currently shut down. Additionally, unlike last February, no visible steam is being vented from the generator building that would confirm that the reactor is operating, but we cannot rule out that this is simply due to the time of year and insufficient image resolution. (Figure 2)

Figure 1. Close-up of new cooling water pump house and in-filled water channel.

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Figure 2. Overview of the 5 MWe reactor.

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The Experimental Light Water Reactor (ELWR)

The four-story engineering office building at the ELWR is now externally complete, with a newly installed concrete driveway leading directly from the building’s entrance to the reactor’s main entrance. (Figure 3) The necessary infrastructure for reactor operations at the ELWR appears externally complete, but there is no visible evidence yet to suggest that operations have begun.

A new small building with a bluish roof has also been erected near the main construction support yard, where only a foundation was previously visible. The purpose of this small non-industrial type building is unknown, but the building appears similar to one that is also newly erected at the Radiochemical Laboratory.

The Kuryong River reservoir that provides cooling water for the Yongbyon reactors appears to be at its intended design levels, and the river seems to be flowing through the diversion sluiceway of the reservoir dam at capacity. It should also be noted that dredging of the riverbed continues upstream of the reactor area; downriver, other earth movements are ongoing.

Figure 3. New engineering office building externally complete and new small building erected at the ELWR.

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The Radiochemical Laboratory

The operational status of the Radiochemical Laboratory (the reprocessing plant used to separate plutonium from spent fuel from the 5 MWe reactor) remains uncertain given the lack of visible vapor coming from the cooling tower. Nonetheless, the site seems active. A large truck is parked near the spent fuel reception building and two trucks are also visible in the motor pool. Another vehicle is outside the security perimeter wall heading south along the access road.

A small blue-roofed building has been erected at the location where we had previously noted a new foundation just north of the cooling tower. (Figure 4) The building appears identical in size and design to the one described above near the ELWR. (Figure 5) Although it is not absolutely clear what role these buildings might serve, they are non-industrial in design, and could have some kind of hospitality role for senior officials.

Figure 4. Small blue-roofed building at the Radiochemical Laboratory.

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Figure 5. New buildings at the ELWR and Radiochemical Laboratory appear identical in size and design.

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At the associated Thermal Plant, the coal bins appear to have been somewhat depleted, suggesting operations at the Thermal Plant have continued. But given the lack of other operational indicators at the Radiochemical Laboratory—for instance, it is difficult to discern whether or not there is any smoke rising from the smokestack on this image—it is also unclear what operations are being conducted. (Figure 6)

Figure 6. Coal bins appear to be somewhat depleted since early May 2018, no obvious smoke plume observed.

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Uranium Enrichment Plant

The increased roof staining at the northwest corner of the cascade halls, as shown in Figure 7, indicates continued operations at the Uranium Enrichment Plant. The staining is caused by the deposition of water vapor coming from the six cooling units associated with gas centrifuge operations. (Figure 7)

Figure 7. Operations continue at the Uranium Enrichment Plant.

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The Radioisotope Production Facility

Since late 2017, two new buildings have been constructed in the southwest corner of the Radioisotope Production Facility near the end of the rail yard line serving that facility. At least one of these new buildings could be intended to store rail-delivered chemicals to support operations in the main production building, as over the past month, a below-grade pipeline has also been completed that connects them with the main production building, thereby providing a possible means for transferring such chemicals. (Figure 8) Little is known about this facility other than it was constructed in 2015, with various modifications since then. However, it is presumed to be a radioisotope production facility based on the internal layout and features observed remotely during its construction.

Figure 8. Pipeline connecting new buildings and main production building recently completed at the Radioisotope Production Facility.

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