• Kyodo


Japanese experts on nuclear and North Korean issues showed mixed views Wednesday over whether Pyongyang succeeded in testing a hydrogen bomb as it claimed, citing seismic data detected around the time of the test and other reasons.

Tatsujiro Suzuki, head of Nagasaki University’s Research Center for Nuclear Weapons Abolition, said Pyongyang may not have gone as far as detonating a hydrogen bomb, but possibly tested a “boosted” fission bomb that is made by adding hydrogen isotopes to an atomic bomb.

“If it was a hydrogen bomb, the size of the earthquake (detected around the time of the purported nuclear test in North Korea) should have been larger,” Suzuki said.

According to the Meteorological Agency, a quake with a magnitude of 5.0 was detected in North Korea around 10:30 a.m. Wednesday Japan Time, which was around the same magnitude level of quakes observed when North Korea conducted nuclear tests in 2006, 2009 and 2013.

But the research center director said he cannot completely rule out the possibility that North Korea, which has conducted three nuclear tests in the past and calls itself a nuclear weapons state, developed a hydrogen bomb because it should already know “the fundamentals” of making the bomb.

“Countries possessing hydrogen bombs have developed them within several years after they made atomic bombs,” he said, adding, “If there are the materials, funds and human resources, it is not impossible” to develop a hydrogen bomb.

Military affairs journalist Osamu Eya was highly skeptical about the claim that North Korea conducted a hydrogen bomb test.

Pyongyang probably tested “a reinforced type of … atomic bomb by adding such elements as deuterium to an atomic bomb and is calling it a hydrogen bomb,” Eya said.

He also said the experiment might have been a failure as the scale of the explosion was apparently smaller than the previous nuclear test in 2013.

But Tetsuo Sawada, assistant professor at Tokyo Institute of Technology, said it is difficult to judge from seismic data whether the tested device was a hydrogen bomb because the size of the quake could change depending on how the device is positioned underground.

“It might have been an experiment of a small-scale hydrogen bomb,” he said.

A hydrogen bomb is a type of nuclear weapon that derives its explosive energy from the nuclear fusion reaction of hydrogen isotopes, such as deuterium and tritium, and can be hundreds of times more powerful than an atomic bomb.

Atomic bombs are called fission weapons, as they use the process of nuclear fission reaction of uranium or plutonium to release energy. Hydrogen bombs use fission bombs for ignition.

Sawada said the possibility that North Korea implemented a hydrogen bomb test will increase if lithium, which is used in the bomb, is detected in the air.

But other experts said Japan’s radiation monitoring system will only be capable of detecting xenon — a radioactive substance that is helpful in estimating whether a nuclear test has taken place — because the system is located far from the nuclear test site

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