The independent resource on global security

Implications of the reported new activity at North Korea’s Yongbyon nuclear complex

Satellite image of the Yongbyon complex. Source: Google, Imagery © CNES / Airbus, Maxar Technologies
Satellite image of the Yongbyon complex. Source: Google, Imagery © CNES / Airbus, Maxar Technologies
Robert E. Kelley

The International Atomic Energy Agency (IAEA) reported on Friday its conclusion that the Democratic People’s Republic of Korea (North Korea) had resumed plutonium production at its nuclear reactor in Yongbyon in early July this year.

The agency also reported that the radiochemical laboratory at the Yongbyon (sometimes written Nyongbyon or Yeongbyeon) complex appeared to have been active early in the year. This laboratory is used to reprocess spent fuel from the reactor, and to separate off plutonium. The length of the activity, between February and July, was ‘consistent with the time required to reprocess a complete core of irradiated fuel from the . . . reactor’ according to the agency.

The 25 MW(thermal) Yongbyon reactor is well known to have produced plutonium for nuclear weapons from as early as the late 1980s. However, this was the first time the IAEA has evidence of the reactor being operational since late 2018, when spent fuel rods were unloaded from it.

It has been estimated that Yongbyon can produce enough plutonium in a year for one or two nuclear warheads.

The IAEA’s conclusions regarding activity at Yongbyon are based only on secondary information, such as satellite imagery, which provides only a limited degree of confidence. For example, satellite imagery only shows indicators like water being discharged system into a river (presumably from the reactor’s cooling system), occasional vehicles, or vapour coming from a ventilation stack.

North Korea announced it had withdrawn from the 1968 Treaty on the Non-Proliferation of Nuclear Weapons (NPT) in January 2003 and no longer considered itself subject to IAEA inspections. Even if there is no legal consensus among diplomatic bodies over whether this move was legal and final, IAEA inspectors have been excluded from the country since 2009.

Nevertheless, the IAEA’s latest warnings are, in its own words, ‘deeply troubling’. As long as North Korea continues to refuse on-the-ground international inspections, the IAEA will have to base its conclusions on indirect observations alone—as it did in Iraq from 1998 to 2001.

Note: It is customary to refer to the power of a military nuclear reactor as its maximum thermal output, which can be easily converted to plutonium production potential. Recent news reports, as well as the IAEA, have instead described the reactor at Yongbyon as ‘5 MW(e)’, which refers to the rating of a tiny electrical generator attached to the reactor. There is no sign that the generator has ever been used. The Yongbyon reactor’s maximum thermal output is ~25 MW(t).


Robert E. Kelley is a Distinguished Associate Fellow at SIPRI.