North Korea’s underground nuclear test shows it is making big strides toward becoming a true nuclear power. But the test may also reveal critical clues about how close — or how far away — the secretive nation is from fielding a nuclear weapon capable of striking the U.S. or its allies.
Hoping to capitalize on a rare opportunity to gauge Pyongyang’s nuclear capabilities, intelligence and military officials around the region are scrambling to glean data to answer three big questions: how powerful was the device tested, what sort of device was it and what progress does the test indicate North Korea has made?
The North hailed Tuesday’s test as a “perfect” success, saying it used a device that was stronger and more advanced than those in its past two attempts. Add that to its successful rocket launch in December and the threat of a North Korea ready to strike at the U.S. would appear to be more real than ever.
But just how close is it?
The main issue is what kind of device was used: Was it a plutonium bomb, like those Pyongyang tested in 2006 and 2009, or one using highly enriched uranium?
James Acton of the Carnegie Endowment for International Peace said the North’s plutonium stockpile is small and it would be difficult and expensive for it to produce more. But a test using highly enriched uranium, which is cheaper and easier to make, would raise the threat that it can expand its nuclear arsenal quickly.
“A highly enriched uranium test would be a significant development,” Acton said. “Unfortunately, we don’t yet have any evidence as to the device’s design yield.”
Finding that out is a race against time.
Joseph De Trani, former head of the National Counterproliferation Center, predicted U.S. intelligence would determine the size and composition of the device in one to three days, based partly on radioactive elements released.
“Highly enriched uranium is something that degrades quickly, so you would have to collect within a 24-hour period,” especially as traces from an underground explosion will be minimal, he said.
Japan may provide some of those answers. Its fighter jets were dispatched immediately after the test to collect atmospheric samples, while it also has land-based monitoring posts to collect data.
But experts caution such monitoring doesn’t always work because test sites can be sealed to prevent tell-tale leaks. They also note that the North has proven it has the ability to mask its tests.
The first indication of the latest atomic test was seismic activity at the test site, which U.S. officials estimated at roughly magnitude 5.1 — equivalent to a medium-sized earthquake. North Korea’s two previous tests registered at magnitude 4.3 and 4.7.
South Korean officials estimate the yield of the device to be between 6 and 7 kilotons. The U.S. has estimated it at “several kilotons.” Either way, it would be the North’s biggest yield yet but far less than that of the 20-kiloton A-bomb dropped on Hiroshima in 1945.
The blast’s size suggests it was, as Pyongyang claims, a success.
“The first test almost failed. The second one showed they could basically do it. The third one showed that this is really working,” said Won Young Kim, a seismologist at Columbia University.
The final intelligence task will be confirming or debunking Pyongyang’s claim that this time around it tested a smaller, more advanced bomb. That is critical because if the North is to mount a nuclear weapon on the tip of a long-range ballistic missile, it must be lightweight.
Experts have long been divided on whether North Korea has made much headway on clearing that hurdle, though the general consensus is it not there yet.
David Albright of the Institute for Science and International Security think tank said, “ISIS has assessed that North Korea still lacks the ability to deploy a warhead on an ICBM (intercontinental ballistic missile), although it shows progress at this effort.”
Even so, Albright stressed the North could be years away from having a credible nuclear weapon that it could launch at the U.S.