North Korea claims H-bomb test: Is that worse than an atomic bomb?

While hydrogen bombs are more powerful, they are also that much more difficult to create.

If North Korea successfully detonated a hydrogen bomb, as state-run news agencies claimed Wednesday, it signifies a significant advancement in the nation's nuclear capabilities.

But why?

A hydrogen bomb, also called a thermonuclear bomb, packs a one-two punch with nearly simultaneous twin explosions, and employs a nuclear fusion reaction for most of its destructive power. This makes it potentially hundreds or even a thousand times more explosive than an atomic bomb.

While H-bombs pose a greater threat, they are also that much more difficult to create.

To initiate the process of nuclear fusion, thermonuclear bombs rely on a two-stage design. In the first stage, conventional high explosives trigger a nuclear fission reaction. The atomic energy released by the first stage initiates a fusion reaction on nearby hydrogen isotopes, creating helium, which, in a chain reaction, triggers nuclear fusion in a second stage usually composed of isotopes of hydrogen or lithium. The results can be extremely destructive.

Like an atomic bomb, hydrogen bombs are measured in megatons of TNT. As powerful as H-bombs are, they also can come in much smaller packages. Most H-bombs can be built compactly enough to be carried by an artillery shell or missile, PBS reports, and are the basis for most nuclear weapons in the arsenals of the US, Russia, France, and other Non-Proliferation Treaty nations.

The three bombs North Korea has tested since 2006 and up to this point have been less sophisticated plutonium-based atomic weapons, say observers. Such weapons were similar to the atomic bombs dropped by US forces on Hiroshima and Nagasaki in 1945 that killed more than 200,000 people, and effectively forced an end to World War II. The US first conducted tests of hydrogen bombs in the early 1950s. 

If North Korea has tested a thermonuclear weapon, it suggests that Kim Jong-Un has a significant addition to his nuclear arsenal.

A few weeks ago, Mr. Kim reportedly declared the country is now "a powerful nuclear weapons state ready to detonate [an] A-bomb and H-bomb to reliably defend its sovereignty and the dignity of the nation,” according to North Korean state-run KCNA news agency.

That assertion – met with global skepticism – may carry more weight following the seismic activity and reports coming from North Korea Wednesday morning: the North’s announcement that it had successfully detonated an H-bomb came an hour after seismic devices picked up a magnitude 5.1 event east-northeast of Sungjibaegam, according to the United States Geological Survey.

Jeffrey Lewis, a nuclear expert at the Middlebury Institute of International Studies at Monterey, Calif., told the Washington Post that Wednesday’s explosion was similar to past tests and was not enormous, suggesting it was not a hydrogen bomb. South Korean lawmakers told local reporters that the explosion had a yield of about six kilotons — making it about the same size as North Korea’s 2013 atomic test.

It could take weeks, or perhaps longer, for US officials to ascertain what kind of tests Kim deployed, according to The New York Times. Ned Price, a spokesman for the White House National Security Council, said in a statement that American officials “cannot confirm these claims at this time.”