16:58 8 January 2016
OPINION: Has North Korea really tested a hydrogen bomb?
By Jeffrey Lewis
MONTEREY, California, Jan. 8, Kyodo
When Kim Jong Un signed the document setting Jan. 6 as the date for North Korea's fourth nuclear test, he did so with a bit of flowery language anticipating the "thrilling explosion of a hydrogen bomb."
Based on seismic readings, the explosion was on the order of 10 kilotons. This is about the size of the U.S. nuclear weapons that were used on Hiroshima and Nagasaki. Such a bomb is far too small to be a thermonuclear weapon, which is much larger, but analysts are increasingly leaning toward the possibility that North Korea used deuterium-tritium gas to "boost" the yield of the explosion.
Deuterium and tritium are isotopes of hydrogen -- so it would only be a slight stretch of the truth to call this a hydrogen bomb. Given how unreliable North Korean propaganda can be, this wouldn't be the worst exaggeration.
Boosting is an important step to miniaturize nuclear weapons. North Korea has repeatedly claimed that it is working to reduce the size of its nuclear weapons, a must if it is to place nuclear warheads on the various missiles, including two ICBMs, that it has paraded through Pyongyang. And it is an important step toward a real thermonuclear weapon.
Boosting is a step that all nuclear weapons states take relatively early in their nuclear weapons program. Even Pakistan claims to have boosted its nuclear weapons, although perhaps this is a boast. There have been indications that North Korea is exploring boosting, including its 2010 announcement of fusion research and analysis that suggests it was building an isotope separation facility at Yongbyon to produce tritium.
The test, then, probably represents a further step toward reducing the size and weight of North Korea's nuclear weapons. This is a danger in a narrow sense, since North Korea may be more able to build nuclear weapons for its growing arsenal of ballistic missiles.
But it is also worrisome in a broader sense. As North Korea pursues increasingly advanced nuclear capabilities, it becomes harder to imagine that it will trade its nuclear weapons for better relations with its neighbors. Denuclearlization may remain the goal of the United States, Japan and other states, but North Korea's test reveals how uncertain we are of how to achieve this.
The development of more advanced North Korean nuclear capabilities does, however, demonstrate the value of seeking a moratorium on nuclear testing on the Korean Peninsula and globally through the Comprehensive Nuclear Test Ban Treaty. Absent such a ban, North Korea will continue to develop more advanced weapons and will, sooner or later, make good on its threat to test a real thermonuclear weapon.
(Jeffrey Lewis is Director of East Asia Nonproliferation Program at the James Martin Center for Nonproliferation Studies (CNS), Middlebury Institute of International Studies at Monterey)