Recent commercial satellite imagery indicates that the 5 MWe plutonium production reactor at North Korea’s Yongbyon Nuclear Scientific Research Center remains shutdown after 10 weeks, longer than what is required for routine maintenance. While it is too soon to reach a definitive conclusion, new evidence is accumulating that suggests: 1) the shutdown may have allowed the North to remove a limited number of fuel rods, possibly failed, from the reactor; and 2) Pyongyang may be preparing to restart the Radiochemical Laboratory, which separates weapons-grade plutonium from waste products in spent nuclear fuel rods.
This assessment is based on three observations: 1) steam coming from a large cooling tower located at buildings associated with the Radiochemical Laboratory is consistent with maintenance, testing and other activities before commencing operations; 2) truck activity near the vehicle door to the building that receives the spent fuel at the reprocessing complex before it is moved to the reprocessing building; and 3) piles of gray material outside the old pilot fuel fabrication facility, now believed to manufacture fuel rods for the 5 MWe Reactor, that may indicate that a chemical process is taking place possibly related to the production of new rods.
In another important development, construction has started on a possible new pipeline that would divert hot water/steam from the reactor cooling system currently dumped in the nearby river to another location, potentially complicating future efforts to monitor operations.
Reactor Remains Shutdown
Recent commercial satellite imagery indicates that the 5 MWe Reactor has remained shutdown for a period of about 10 weeks, longer than what routine maintenance would require. As noted by the Institute for Science and International Security in its October 3 analysis, indicators of reactor operation—steam venting from the turbine building and hot water/steam emitting from the secondary cooling systems discharge pipeline—were not present during this period. Imagery from October 28 and November 4 shows the continued absence of those indicators.
Figure 1. The 5 MWe Reactor appears to still be shutdown in October.
Figure 2. Little change by early November.
New Unidentified Activity at the Reprocessing Complex
Imagery also indicates new activity at Yongbyon’s Radiochemical Laboratory, the facility where weapons-grade plutonium is separated from the waste products in the 5 MWe Reactor’s spent fuel rods. Throughout the summer and into fall 2014 there was little activity at this facility. However, on November 4, steam was seen rising from a large cooling tower at auxiliary buildings just southeast of the plutonium separation building. These buildings contain repair workshops, chemicals for the complex, and waste treatment plants.
Figure 3. New activity seen at the Radiochemical Laboratory.
In the same image, three vehicles—two trucks and one unidentified vehicle—are seen on the road in front of the door to the spent fuel rod receiving building at the reprocessing complex. The truck closest to the door is a white, possibly box-bodied vehicle; the second, a smaller truck surrounded by three or four people; and the third, possibly a trailer.
Figure 4. Trucks and other vehicles seen at the Radiochemical complex.
There has been uncertainty about the reasons for the 5 MWe Reactor’s shutdown, with speculation focusing on routine maintenance, more serious problems possibly with the cooling systems, a partial unloading of fuel rods (possibly defective) or the removal of the entire core. Evidence from the most recent imagery, while still insufficient to make a firm judgment, would seem to reinforce the hypothesis of a partial unloading of fuel rods. (Those rods would be transported underground from the reactor to the spent fuel cooling pond and then moved to the reprocessing facility by trucks or vehicles.)
The activity noted to support this hypothesis includes:
- Steam coming from a nearby large cooling tower is consistent with maintenance and testing (as well as possibly the making of chemicals related to reprocessing) and would be one of the first steps taken before commencing operations.
- Truck activity near the vehicle door to the receiving building is consistent with the transport of spent fuel rods from the cooling pond (where they are stored after removal from the reactor via an underground trolley system) and before they are moved to the reprocessing facility.
- Growing piles of a gray substance are visible on the east side of the old pilot fuel fabrication plant, now believed to manufacture fuel rods for the 5 MWe Reactor, as well as at a nearby settling pond. These piles are possibly the result of chemical processes related to new fuel rod production taking place inside the facilty.
Figure 5. Gray piles are seen on the east side of the pilot fuel fabrication plant.
New Pipeline under Construction: Masking Future Operations?
The October 28 imagery also indicates that the North Koreans may be building a new pipeline running from the pipe that carries hot water and steam from the 5MWe Reactor turbine building to the river. A new trench heads north under the bridge and seems to end across the road from the pilot fuel fabrication building. The final destination of the pipeline remains unclear. At the northern end of the trench, a crane or backhoe is visible just off the road. No further work on this pipeline appeared in imagery from November 4.
Figure 6. New trench work being done.
One objective of this activity may be to eliminate a key indicator of 5 MWe Reactor operations. Observing the white froth from the steam and water discharged into the river helped private analysts determine that the reactor restarted in August 2013 as well as the short period when it has been shutdown over the past year. Without this indicator, determining what is happening at the facility will become more difficult.
Masking operations at nuclear facilities may be an important priority for North Korea if past actions are any guide. Since the mid-2000s, if not earlier, Pyongyang appears to have taken steps intended to severely limit the ability of outsiders to monitor activity at the Radiochemical Laboratory. The same appears true at North Korea’s Punggye-ri nuclear test site where extensive steps have been taken to hide preparations at tunnel entrances and to prevent the leakage of particles from nuclear tests that could provide significant information of its capabilities to other countries.
 The facility was last used in 2009 but has been maintained since then.
 It is worth noting that, in the past, ash has been stored by the North Koreans in containers since the fine particles contain uranium and mixing it with water could cause serious health problems.