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What is a miniaturized hydrogen bomb?

“Ivy Mike” explodes in the Pacific Ocean in 1952.
By Heather Timmons
Published Last updated This article is more than 2 years old.

North Korea successfully tested a “miniaturized H-bomb,” an announcer on the isolated country’s state-run television station said Wednesday, weeks after leader Kim Jong-un said the country had successfully developed a hydrogen bomb.

The country’s claim is already being refuted by nuclear experts. If true, it signals a significant escalation in North Korea’s weapons arsenal. The country has tested nuclear weapons three times before, but a miniaturized hydrogen bomb could pose a bigger threat to North Korea’s neighbors, the region, and countries around the world.

Miniaturization, first of all, has been applied to nuclear weapons for decades, to allow them to be loaded onto long-range missiles. North Korea claimed last May it had developed the capacity to miniaturize nuclear weapons, a claim that many defense experts disputed. At the time the US National Security Council said, though, that North Korea was developing long-range missiles that could threaten the US.

Hydrogen bombs are a more sophisticated and difficult-to-make form of nuclear weapon than atomic bombs, because they rely on a two-stage process that includes the fusion (combination) of atoms, rather than just the fission (splitting) of atoms.


This difference—and this is the terrifying part—is part of the reason hydrogen bombs are much stronger, as Popular Mechanics explains:

H-bombs are much more powerful—while nuclear bombs are often in the kilotons (one kiloton equals 1,000 tons of TNT) hydrogen bombs are usually in the megatons (one megaton equals 1,000,000 tons of TNT).

“Ivy Mike,” the first hydrogen bomb ever tested by the US Atomic Energy Commission and Department of Defense in 1952, was 10.4 megatons, and military reports (pdf, pg. 192) say it sent heatwaves as far as 35 miles (56 km) away. “Fat Man,” the atomic bomb detonated over Nagasaki in 1945 that killed about 40,000 people instantly, was 21 kilotons in comparison.

Even though the detonation caused tremors Wednesday that registered as a 5.1 magnitude earthquake, some North Korea watchers remained skeptical the country had, in fact, developed a hydrogen bomb.

South Korea’s meteorological agency said it had not detected any radiation after North Korea said it had tested a bomb.

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