North Korea’s Yongbyon Nuclear Center: Flood Damage Repairs Underway

Commercial satellite imagery from October 17 of the Yongbyon Nuclear Scientific Research Center indicates that North Korea has begun repairing damage caused by the late-summer floods to the reservoir overflow dam, which is used to maintain a constant source of water for the cooling systems of both the 5 MWe Reactor and the Experimental Light Water Reactor (ELWR). Some activity also continues around the cooling units of the Uranium Enrichment Plant (UEP), although the exact nature of it remains unknown.

Reactor Area

Between September 22 and October 17, repair work began on the cooling water reservoir overflow dam in the Kuryong River, which was breached by the floodwaters of August. Two pump houses, which are meant to feed water through the reactors’ cooling systems, have been put through extremes over the past two months. Imagery from August 6 showed that the river had reached a level that appeared to put both pump houses at risk of flood damage, although subsequent imagery indicated they were spared any significant or discernable impairment.

Imagery from September 22 then showed a dramatic drop in the water level of the reservoir due to a breach in the overflow dam. Had the reactors been running, this would have prevented sufficient cooling water from being available via the pumps and cistern network. It is worth noting, however, that there have been no signs this year that the 5 MWe Reactor has been running or that the Experimental Light Water Reactor has been brought online.

The overflow dam is designed to maintain a constant reservoir water level by allowing excess water to overflow its top with a sluiceway located at the west end, just below the pump house which services the ELWR. The break in the dam occurred at its east end. By October 17, work had started on the silt area below the dam to excavate and build up the area. Additionally, a dike-like structure is being created immediately west of the break, which extends diagonally north from the dam to the far bank of the river, following a former sandbar. It is not clear whether the dike is being constructed to create a more favorable reservoir or is simply meant to divert the water away from the break in order to enable repairs to the damaged section.

Figure 1. Repair work at the overflow dam.

Other Activity

While harvesting activity in the surrounding area continues, grain drying on open surfaces within the compound has diminished.

At the Main Research and Administrative Headquarters Area, a new foundation is being prepared on the east side of a building previously reported under construction. Whether it will be a second structure or become a part of a now larger structure is unclear.

Figure 2. Construction underway at the Main Research and Administrative Headquarters Area.

At the bridge-causeway located to the west of the UEP, construction crews continue to build up the banks of the mid-river island they created. The work is likely to ensure that the channels created will not be easily erased by future floods and to keep open flow through a small sluice gate near the eastern bank.

Figure 3. Bank building activity at the bridge-causeway.

Uranium Enrichment Plant (UEP)

At the UEP, the exact nature of the work being done on and around the cooling units, whether refurbishment or unit replacement, remains unknown. This activity apparently began in early April, but insufficient imagery resolution of this area since then has precluded any clarification of what is being observed. In the October image, there appears to be something obscuring the area around what could be two large replacement cooling units located inside the east end of the courtyard. However, once again, it is not possible to determine exactly what is being observed.

Figure 4. Close-up of cooling units at the Uranium Enrichment Plant.