A 38 North exclusive with analysis by Nick Hansen and Jeffrey Lewis

New commercial satellite imagery of North Korea’s Yongbyon nuclear facility indicates that Pyongyang is probably restarting its 5 MWe gas-graphite plutonium production reactor. Since announcing in early April 2013 its intention to restart this reactor, work has progressed rapidly over the spring and summer to bring the facility back into operation. In June 2013, 38 North predicted that the reactor would be ready for restart by the end of August.

Satellite imagery from August 31, 2013 shows white steam rising from a building near the reactor hall that houses the gas-graphite reactor’s steam turbines and electric generators. The reactor generates electricity by using the heat from the nuclear reaction in the core to create steam that spins the turbines. The white coloration and volume are consistent with steam being vented because the electrical generating system is about to come online, indicating that the reactor is in or nearing operation.

The 5 MWe reactor is capable of producing six kilograms of plutonium a year that can be used by Pyongyang to slowly increase the size of its nuclear weapons stockpile.

Construction Completed

North Korea completed the 5 MWe gas-graphite plutonium production reactor in the 1980s. After the first nuclear crisis, North Korea agreed to shutdown the reactor under the 1994 Agreed Framework. When that arrangement collapsed in 2002, Pyongyang restarted the reactor only to disable it once again under the terms of a Six Party Talks agreement, concluding in the televised demolition of the facility’s cooling tower in June 2008. Between 1985-1994 and 2002-2007, the reactor produced 34-36 kilograms of plutonium, enough for about a dozen nuclear weapons.

In early April 2013, North Korea announced that it would restart the facilities at Yongbyon, including the 5 MWe gas-graphite reactor “without delay.” Shortly after the announcement, 38 North noted Pyongyang did not need to rebuild the cooling tower, but could instead connect the existing reactor to a newly built pump-house near the Experimental Light Water Reactor (ELWR) also under construction at the site. (North Korea constructed a copy of the Yongbyon reactor in Syria that used a pump-house sited on a river instead of a cooling tower.) Subsequent satellite imagery published by 38 North confirmed this activity as well as a rapid effort over the summer to restart the reactor. At the time, 38 North noted that the reactor may be “1-2 months from start-up”—August 2013.

White Steam Rising

North Korea now appears to have put the reactor into operation. New commercial satellite imagery from August 31 shows white steam rising from a building near the reactor hall. The building in question houses the gas-graphite reactor’s steam turbines and electric generators. IAEA officials, including then Director General Hans Blix, visited the building in 1992, examining the turbines and electrical generators located on the building’s second floor. It is possible to match video footage of the interior with exterior images of the building in satellite images, based on the distinct pattern of the windows.

The reactor generates electricity by using the heat from the nuclear reaction in the core to create steam that spins the turbines. The white coloration and volume are consistent with steam being vented because the electrical generating system is about to come online, indicating that the reactor is in or nearing operation. (In the past, steam emissions from the cooling tower were one among many indicators that the reactor was operating. This is no longer possible now that North Korea uses the river and pump-house for secondary cooling.)

The 5 MWe reactor is capable of producing 6 kilograms of plutonium a year that can be used by Pyongyang to slowly increase the size of its nuclear weapons stockpile.

Figure 1. Steam seen coming from the electrical power generating building.

Figure 2. A steam turbine inside the electrical power building.

Figure 3. Ground view of the 5 MWe reactor showing the external elevated steam line.