Jeffrey LewisNew Construction at Yondoktong

Zach Cohen and Kylie Atwood have a story at CNN (New satellite images reveal North Korea took recent steps to conceal nuclear weapons site) that builds on some work Dave Schmerler and I did using images from Maxar.

North Korea recently built a structure near Yongdoktong, where it stores its nuclear weapons, apparently to disguise the entrances to a pair of underground tunnels.

Among other things, Cohen and Atwood very helpfully got a senior US intelligence official to confirm “Yongdoktong has been previously identified by US intelligence as a suspected North Korean nuclear weapons storage facility and is still believed to be used for that purpose” — something Ankit Panda reported in his book, Kim Jong Un and the Bomb.

Here is the write-up that Dave Schmerler and I prepared, plus a little gif at the end.

New Construction at North Korea’s Yondoktong Nuclear Weapons Site

Jeffrey Lewis and David Schmerler

North Korea maintains a significant nuclear weapons research and development site at Yongdoktong, near Kusong.  New satellite images taken by Maxar show that North Korea sometime in the past year built a structure that may be intended to obscure entrances to an underground facility where nuclear weapons or nuclear weapons components are stored. 

Image taken on February 11, 2021 by Maxar showing the new structure obscuring the entrance to the a pair of tunnels at Yongdoktong.

The Yongdoktong (용덕동) site is well-known to American and allied intelligence communities and its name has often appeared in the press.  The existence of the site was first disclosed in the late 1990s, after US officials briefed their South Korean and Japanese counterparts about the shift of high-explosives testing from Yongbyon Nuclear Science Center to Yongdoktong. At this time, a poor quality satellite image of the Yondoktong site was printed in a Japanese news magazine. (“North Korea’s ‘Nukes’ Place World in ‘Crisis’ Again” Tokyo Shukan Posuto (in Japanese), 16 April 1999.) We used this image to geolocate the site, which is located at: 40.0286, 125.3102°.

Left: The Yongdoktong site today (Source: Google Earth); Right: The site in circa 1999 (Source: Shukan Posuto).

Yongdoktong reappeared in the news in 2003 when David Sanger reported in The New York Times that the United States had briefed allies in South Korea and Japan on the existence of “an advanced nuclear testing site in an area called Youngdoktong. [sic] At the site, equipment has been set up to test conventional explosives that, when detonated, could compress a plutonium core and set off a compact nuclear explosion.” Asian news outlets also reported on the briefing. High-explosive testing would usually be located at or near a country’s main nuclear weapons research and development facility. 

Yongdoktong is also of interest because it appears to be North Korea’s sole nuclear  weapons stockpile site.  “As of late 2017, the U.S.  assessment is that North Korea operates a single storage site for its manufactured warheads and their fissile cores,” Ankit Panda reported in his book Kim Jong Un and the Bomb, “an underground facility known to the United States as Yongdoktong, northeast of the city of Kusong.”  

The Yongdoktong site appears to host multiple nuclear weapons related facilities, including high-explosives testing and a warhead storage site. These facilities are strung along a mountain valley east of Kusong that stretches about nine kilometers.  There are numerous tunnels and underground facilities at the site, as well as office buildings, industrial buildings and housing.  

Unsurprisingly, the Yongdoktong site is a major subject of scrutiny by the US and allied intelligence communities.  In September 2018, US intelligence agencies identified a number of activities at Yongdoktong that analysts believed were inconsistent with hopes that North Korea might abandon its nuclear weapons programs following then-President Donald Trump’s meeting in Singapore with Kim Jong Un.   “The newest intelligence shows Kim’s regime has escalated efforts to conceal its nuclear activity, according to three senior U.S. officials,” reported Courtney Kube and Carol Lee. “During the three months since the historic Singapore summit and Trump’s proclamation that North Korea intends to denuclearize, North Korea has built structures to obscure the entrance to at least one warhead storage facility, according to the officials.”  At the time, those of us in civil society did not see unambiguous evidence in commercial satellite images that could corroborate these claims.  We did observe some changes in this time period at a tunnel entrance located at: 40.0148, 125.326.  

Now, however, it is clear that such structures are being built.  New satellite images provided by Maxar show that sometime in 2020, North Korea constructed a building-like structure that now obscures a pair of tunnel entrances previously identified at the Yongdok nuclear weapons site.  Images released by Maxar show the pair of tunnel entrances as late as December 2019 and a new building-like structure visible by February 2021.

You can slide compare images from December 5, 2019 and February 11, 2021 using a slider. Both satellite images: ©2021 Maxar Technologies.

North Korea has obscured the entrance to other underground facilities in the same way.  During a 1992 IAEA visit to the Yongbyon nuclear complex, then-director Hans Blix was given a tour of an underground complex. The entrance was designed to look like a building set against a hillside.

Scenes from IAEA visit to the Yongbyon nuclear complex in 1992 – prior to and during a tour of an underground storage site (Source: Youtube – IAEA footage of Director General Hans Blix touring North Korean Nuclear Sites in 1992 / Institute for Science and International Security ).
Location of the underground complex visited by the IAEA with building obscuration located at  39.800924, 125.762056 (Source: GoogleEarth/Maxar date: 03/20/2020)

It is unclear what purpose of the structure at Yongdoktong serves.  One interpretation is that North Korea is attempting to obscure movement of nuclear warheads and nuclear weapons components in and out of tunnels at the Yongdoktong site.  Given that the location is well-known to foreign intelligence communities, however, it seems the value of the new structure is limited.  Another possibility is that the new structure provides additional room for loading and unloading of nuclear-weapons related cargos which cannot be seen in overhead imagery. Overall, however, the structure serves to remind us that North Korean possesses and continuously maintains a significant infrastructure for the production of nuclear weapons.