Recent commercial satellite imagery has identified two new tunnel entrances and continued excavation at the Punggye-ri nuclear test site. Excavation in the West Portal area, where North Korea’s 2009 and 2013 nuclear tests were conducted, and the South Portal area may be intended to complete new tunnels that will be used for future nuclear tests. An alternative explanation, particularly for work in the West Portal area, is that North Korea is digging a secondary entrance to a nearby existing tunnel intended, for example, to allow increased traffic flow or ventilation. Whether Pyongyang is following this practice remains unclear. Continued observation of excavation at Punggye-ri should reveal additional information since it may take as long as one to two years to dig separate new tunnels.
There are no signs that Pyongyang plans to conduct a nuclear test in the immediate future. However, these ongoing activities as well as upgrades to the site’s support areas indicate North Korea is preparing to conduct additional detonations in the future as part of its nuclear weapons development program.
New Tunnel Entrance in the West Portal Area
Commercial satellite imagery from September 27, 2013 indicates continued excavation in the West Portal area, site of the 2009 and 2013 nuclear detonations, and the presence of a new tunnel entrance (adit) (figure 1). Imagery from a month earlier shows the head works—the framing for the tunnel entrance—and cart tracks leading into the entrance, only to be covered by what is probably a camouflage net by late September (figure 2). Imagery from 2009 gives a clearer view of entrances probably used in the earlier tests in relationship to the new entrance (figure 3).
Figure 1. Key developments in West Portal area.
Figure 2. New tunnel entrance at the West Portal.
Figure 3. Possible tunnel entrances for the 2009 and 2013 tests.
Digging of the tunnel may have begun when spoil was first spotted in mid-May 2013 and continued through late September (figure 3). The imagery appears to show the pile increasing gradually over that time period, even between the last two photos taken just two days apart. Estimating the size of the pile is difficult since the location is very steep and spoil may be sliding down the hill. Still the amount appears to be significant given the fact that tunneling has only taken place over the past five months.
Figure 4. Gradually increasing spoil pile.
Possible New Entrance at the South Portal Area
New imagery indicates what may be a second tunnel under construction just off the main road in the South Portal area (figure 5). Work may have started as early as late-2011 when the second spoil pile was seen initially in satellite imagery. Identification of the entrance has proven difficult since this area, located on the northern side of the mountain, is normally in shadows as well as obscured by the mountain and overhanging trees. The July 2013 image was taken from the north with the sun at a high angle, allowing details of this area to be seen.
Figure 5. Possible second tunnel entrance.
Heavy rains in mid-July 2013 may have delayed work at the site. The main road into the facility, just below the bridge at the South Portal, initially damaged by rain in 2012, was further eroded by the overflowing stream and partially fell into the canyon. As a result, no vehicles may have been able to reach the main facility for several weeks until a new bypass road was built (figure 6).
Figure 6. South Portal area before and after mid-July 2013 flood damage.
Imagery in September indicates new spoil dumped on the stream side of the road just south of the washed out section, probably to shore up the new road (figure 7). It also indicates that tunneling is still ongoing at the South Portal area.
Figure 7. New spoil pile at the South Portal.
Support Areas Upgraded
In addition to two new tunnel entrances and continued excavation, satellite imagery has also identified construction activities probably intended to upgrade support facilities at the test site. Construction and building repair is ongoing at the main support area where administrative headquarters, troop barracks and storage facilities are located. (In the months prior to the February 2013 nuclear test, increased activity at the main support site indicated that a test might well be in the works.) A new building (whose purpose is unclear) is seen under construction as of September 27. Moreover, a new wooden roof has been installed on the main support building that was previously seen being repaired in June 2013 (figures 8 and 9).
New imagery also indicates that a large building at the West Portal area, possibly related to tunneling activities, was partially dismantled by early July and by late September, is being rebuilt. Also, there is a new building near the creek crossing bridge that could be a guardhouse intended to better restrict access to the West Portal.
Figure 8. Support Area in July.
Figure 9. Support area in September with new building under construction.
The appearance of two new tunnel entrances and continued excavation at the West and South Portal areas may indicate that Pyongyang is preparing additional tunnels for future nuclear tests. An alternative explanation, particularly for work in the West Portal area, is that the new tunnel is a secondary entrance to a nearby existing tunnel, intended, for example, to allow increased traffic flow or ventilation. Whether Pyongyang is following this practice remains unclear. Continued observation of excavation at the site could reveal additional information, particularly since it may take as long as one to two years for North Korea to dig separate new tunnels.
There are no signs that Pyongyang plans to conduct a nuclear test in the immediate future. However, these activities as well as upgrades of support areas at the Punggye-ri nuclear test site indicate that North Korea is planning to conduct future detonations as part of its overall nuclear weapons development program.
 In the past, nuclear powers have excavated secondary entrances to main test tunnels and conducted multiple tests in branches off the tunnel by sealing the blast areas.
 Approximately one half the logs and lumber piles that have been seen in the parade area since March 2013 disappeared by late August and were completely gone by late September. The wood was probably used for various activities including construction of the new roof, the new building and tunneling supports at the West and South Portals. This activity indicates that the test site cuts its own logs, produces its own lumber and uses the material on site. There appears to be no current logging activity, indicating that the North Koreans may have cut what is needed for ongoing work.
 In the past, nuclear powers have excavated secondary entrances to test tunnels and conducted multiple detonations in branches off the main tunnel by sealing the blast areas.