WORLD

North Korea says it has carried out an underground test of a hydrogen bomb, but Western observers are skeptical. What’s the big deal? (BBC)

Use our resources to learn more about the U.S.’s own testing of H-bombs.

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit, including today’s MapMaker Interactive map.

Discussion Ideas

• Hasn’t North Korea tested nuclear weapons before?
  • Yes. According to the BBC, North Korea’s nuclear program has “been a source of great concern for the international community for more than 20 years.”

 

• So why is this test such a big deal?
  • North Korea is claiming to have detonated a hydrogen bomb, not simply an atomic bomb. If North Korea’s claims are true, this would be a huge advancement in its nuclear program.

 

• Hydrogen bombs and atomic bombs are both nuclear weapons, right?
  • Yes, both hydrogen bombs and atomic bombs are nuclear weapons with their explosive power measured in yield, which is expressed in tons of TNT.

 

• OK, so what’s the difference?
  • One is bad, the other’s worse. Here’s the best comparison I’ve seen.
    • Bad: Atomic bombs derive their power from nuclear fission, and are sometimes called fission bombs. During the process of nuclear fission, an atom splits apart, releasing photons, neutrons, and an enormous amount of energy. The principal fuels in atomic weapons are isotopes of plutonium and uranium; when a neutron hits the nucleus of these isotopes, the nucleus splits. (This is a complex, delicate process with some unusual consequences—read about them here.) When you have a critical mass of these isotopes, a nuclear chain reaction can be sustained—the neutrons released by the initial split initiate more splits. Boom.
      • Although many nations have developed atomic weapons technology (take a look at the map here) the United States is the only country to have deployed such weapons in combat. “Little Boy,” the weapon dropped on the Japanese city of Hiroshima in 1945, used the isotope uranium-235. Its yield was about 15,000 tons of TNT. “Fat Man,” the weapon dropped on the Japanese city of Nagasaki a few days later, used plutonium-239. Its yield was about 20,000 tons.
      • The most powerful atomic bombs have a yield of about 500,000 tons of TNT.
    • Worse: Hydrogen bombs, sometimes called thermonuclear bombs or simply H-bombs, derive their power from both nuclear fission and nuclear fusion. Most hydrogen bombs are two-stage devices, although the stages happen at virtually the same time. The first stage is a nuclear fission explosion (described above). In the second stage, extreme heat and pressure from that explosion force two hydrogen isotopes (deuterium and tritium) together. Deuterium and tritium fuse to create another element—helium. Some hydrogen bombs include a third stage, which mimics the nuclear fusion of the second. The energy from nuclear fusion cycles back to the original fission reaction, increasing its yield. Big boom.
      • Hydrogen bombs have never been deployed in combat.
      • The most powerful man-made explosion in history was a hydrogen bomb (possibly three-stage) tested by the Soviet Union in 1961. “Tsar Bomba” had a yield of about 50,000,000 tons of TNT—that’s right, 50 million tons. Its flash could be seen from a distance of 270 kilometers (170 miles) and its mushroom cloud extended about 64 kilometers (40 miles) into the atmosphere.

 

• What other countries have deployed H-bombs? Take a look at today’s MapMaker Interactive map for some help.
  • Not very many. The only confirmed tests have been limited to the United States, the United Kingdom, France, the Soviet Union, and China. (That group sound familiar?) Newer nuclear powers such as Israel, India, Pakistan, and, now, North Korea are rumored to have tested hydrogen bombs, but there isn’t definitive proof.

 

• North Korea is claiming to have deployed its H-bomb in an underground test. What does this mean?
  • Underground testing is one of the safest ways to test nuclear weapons. When the device being tested is buried deep enough, the explosion may be contained, with no release of radioactive materials to the atmosphere.

 

• North Korea is a secretive society. How do we know a test took place at all?
  • Underground nuclear testing triggers earthquakes that are easily detected by sensors around the world. The good folks at the USGS, for instance, were able to measure the North Korean test as a magnitude 5.1 earthquake.

 

• Why are experts skeptical about North Korea’s claim?
  • Measuring seismic waves from the test-triggered quake indicates the weapon’s yield was about 10,000 to 15,000 tons of TNT. This is much, much smaller than the approximate 100,000-ton marker of an H-bomb—which would have triggered around a magnitude 7 earthquake. Here’s a good graphic comparison.
    • Having said that, the depth of the test could easily allow the results to be misinterpreted; it is possible the Hermit Kingdom could have detonated a small hydrogen bomb.

 

• When will we learn more?
  • If radioactive material was vented out from the underground test, it could be easily sampled in the atmosphere as it reaches neutral airspace. According to the BBC, “the U.S. will fly its WC-135 Constant Phoenix aircraft to analyze the atmosphere off the North Korean coast. Other countries will also perform their own sampling, but ‘there is no guarantee that anything will leak’.”

 

TEACHERS’ TOOLKIT

BBC: North Korea ‘H-bomb test’: What do we know?

Nat Geo: Castle Bravo

Nat Geo: What countries have tested hydrogen bombs? MapMaker Interactive map

Nat Geo: What countries have access to nuclear weapons? MapMaker Interactive map

BBC: North Korea’s nuclear tests

New York Times: Why Experts Doubt North Korea Tested a Hydrogen Bomb

USGS: M5.1 Nuclear Explosion – 22km ENE of Sungjibaegam, North Korea

PBS NewsHour: Types of Nuclear Bombs