Punggye-ri Update: New Activity at Tunnel No. 4

Key Findings

• Recent satellite imagery of the Punggye-ri Nuclear Test Facility shows new activity at the site.
• The road leading to the collapsed portal for Tunnel No. 4 has been completed, and two new small buildings have recently been constructed in front of the collapsed portal.
• A clear view of the portal to Tunnel No. 3 shows cables running from two nearby structures into the portal. There is water drainage from the portal, which is expected as the tunnel is sloped.
• There is no activity at the collapsed Tunnels No. 1 and 2.
• Although the recently observed activity is not a strong indication of imminent testing, the long-anticipated seventh nuclear test will almost assuredly take place at the Punggye-ri Nuclear Test Facility.

During President Yoon’s state visit to the White House last week, the two nations announced the Washington Declaration, which aims to strengthen extended deterrence by establishing a shared decision-making framework and the Nuclear Consultation Group (NCG). The state visit came against the backdrop of increasing tension between the two Koreas for North Korea’s “unilateral” severance of the cross-border hotline.¹ Imagery taken during this time, on April 21, 2023, shows that North Korea has resumed long suspended activity at Punggye-ri.

Tunnel No. 4

Most notably, the construction activity of the road leading to the collapsed portal for Tunnel No. 4 (also known as the West Portal), which was suspended for several months, has now been completed. Additionally, two new small buildings were constructed in front of the collapsed portal.

Although activity has resumed outside of Tunnel No. 4, the former portal still remains collapsed. To make Tunnel No. 4 viable again, the extensive support cribbing previously seen above would have to be rebuilt. It remains unclear whether this new activity at Tunnel No. 4 is designed to expand North Korea’s nuclear testing capabilities beyond Tunnel No. 3 or simply a component of a strategic deception plan. However, the new structures outside of the portal indicate that work to open the collapsed tunnel may resume in this area of the facility.

Tunnel No. 3

In one of the clearest images of the portal to Tunnel No. 3 (also known as the South Portal) to date, cables are seen running from two nearby structures into the portal. There is also water drainage from the portal. Such activity is expected as the tunnel is sloped and does not necessarily indicate any imminent testing activity. Preparations for conducting a test have been assessed to have been complete for nearly a year.²

Main Administration and Support Area

Only minor activity is observed at the main administration and support area. The wood piles at the open-air lumber yard have reduced in size, indicating ongoing construction work throughout the facility.

Tunnels No. 1 and No. 2

The April 21, 2023, image continues to show no activity at either of the remaining two tunnels at the Punggye-ri Nuclear Test Facility—Tunnel No. 1 (East Portal) and No. 2 (North Portal).