Monitoring Activity at Yongbyon Nuclear Site

by David Albright and Serena Kelleher-Vergantini

April 23, 2014

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Recent commercial satellite imagery shows that North Korea’s 5MW reactor at the Yongbyon nuclear site continues to be active, despite claims if inactivity.

5 MWe Reactor and Light Water Reactor (LWR)

Since August 2013, commercial satellite imagery shows that water is being discharged near the 5 MWe reactor. This outflow water is being discharged into the river through a pipeline buried east of the reactor. Recent imagery continues to show that water is being discharged (see figure 1), suggesting that the 5 MWe reactor is operating.

This water discharge is most likely used to as part of a secondary cooling system use to cool the carbon dioxide gas from the 5 MWe reactor core. ISIS believes that the 5 MWe reactor’s primary cooling system receives water through a very long piping system connected to a pump house north of the reactor (see figure 1).

The presence of the inflow piping and the continuous discharge of water from the outflow piping system signify testing or on-going operation of the 5 MWe reactor. However, this conclusion results from an assessment given that no steam is seen originating from the reactor.

Centrifuge Plant

The gas centrifuge enrichment plant at Yongbyon is believed to be producing low enriched uranium (LEU) fuel for the light later reactor (LWR) or for further enrichment to weapon-grade an Yongbyon or elsewhere. In August 2013, ISIS noted that North Korea had been expanding its gas centrifuge plant at Yongbyon, therefore potentially doubling its enrichment capacity. In a December 2013 ISIS Imagery Brief, ISIS highlighted that North Korea had renovated an additional section of the old roof in the original building that appears to be part of the centrifuge plant (see figure 2).

However, recent imagery does not show any significant alterations at the gas centrifuge enrichment plant. It is plausible that centrifuges and related equipment are being installed at this time.


  • Monitoring Activity at Yongbyon Nuclear Site  Photo
    Figure 1. Digital Globe imagery showing North Korea’s Yongbyon 5 megawatt-electric (MWe) and experimental light water reactors, and the respective water inflow and outflow systems of the 5MWe reactor on April 7, 2014.
  • Monitoring Activity at Yongbyon Nuclear Site  Photo
    Figure 2. Digital Globe Imagery showing the status of North Korea's Yongbyon Fuel Fabrication Complex and Uranium Centrifuge Plant (bright blue roofed building) on April 7, 2014.

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