A decade ago, the last time North Korea took talks with the U.S. so far, then-leader Kim Jong Il blew up a cooling tower at the Yongbyon nuclear plant as part of a deal to limit its weapons program. Within months, he was reassembling the reactor — a key source of weapons-grade plutonium. That’s one reason why arms-control experts are watching with caution as his son, Kim Jong Un, now moves to publicly dismantle the remote subterranean testing site used by the regime to detonate six nuclear bombs.
1. What’s Kim planning?
Days before his historic summit with South Korean President Moon Jae-in last month, Kim announced plans to close his Punggye-ri testing ground in the country’s mountainous northeast. The regime later said it would invite journalists from China, Russia, the U.K. and the U.S. between May 23 and May 25 to observe the collapse and closing of test tunnels and other facilities. U.S. President Donald Trump praised the move as a “very smart and gracious gesture” ahead of his own planned meeting with Kim next month in Singapore.
2. What facilities is he closing?
The site is believed to house three tunnel complexes surrounded by granite bedrock ideal for containing large explosions. The area — situated between the Chinese border and the Sea of Japan — provides a “virtually infinite amount of space” for underground testing, according to Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute of International Studies in Monterey, California.
3. Has the site been damaged during testing?
Yes, but not enough to render it unusable, according to 38 North analysts Frank Pabian, Joseph Bermudez Jr. and Jack Liu, who monitor North Korea’s weapons program using satellite imagery and other data. The southern and western portals could still support detonations, even if the northern side was badly damaged over the five nuclear tests conducted there, 38 North said April 30. That analysis appeared to support Kim’s own claim that two tunnels were still in good condition.
4. Does North Korea need more tests?
Possibly not. Both India and Pakistan established themselves as nuclear powers after a similar number of tests — and neither has detonated a bomb since 1998. In his April 20 statement announcing the Punggye-ri closing, Kim said the country’s efforts to build a warhead small enough to fit on a ballistic missile had progressed to the point where tests were no longer necessary. Still, it’s unclear whether North Korea has figured out how to prevent a warhead from burning up during re-entry from space.
5. Would the site’s closing be permanent?
No. A 38 North analysis of satellite images taken May 7 showed that several support buildings outside the northern, western and southern portals had been razed while some mining cart rails had been removed. Such facilities can be replaced as easily as the Yongbyon cooling tower. Lewis, of the Middlebury Institute, argues that the tunnel’s horizontal layout would also make it relatively easy to “pop” open the sealed entrances and regain access after their closing.
6. What about building a new tunnel?
A new test site could be constructed in three to six months, depending on how much labor was thrown at the job, according to Suh Kune Y., a nuclear engineering professor at Seoul National University. Future detonations — most likely to test warhead miniaturization — might only require a simple straight tunnel with one right angle at the end, he said.
7. What about other sites?
North Korea, which is believed to manage a vast subterranean network in part to frustrate U.S. and South Korean spies and military planners, probably has other locations that could house tests. Suh pointed out that North Korea refers to the Punggye-ri facility as its “northern test site,” possibly implying there are others. And, of course, tests don’t need to be underground. In September, North Korea Foreign Minister Ri Yong Ho suggested that his country could detonate a hydrogen bomb over the Pacific Ocean.
