Decoding the Levels of Danger

Question: How do we know that North Korea detonated a nuclear device?

Answer: We know that a seismic event consistent with a large underground explosion was detected in northeastern North Korea. The U.S. Geological Survey measured the event at magnitude 4.2; the South Koreans said the magnitude was 3.6. Monitors will need to analyze sound waves and any particles and gases that leaked from the explosion site to determine what was detonated.

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Q: How does the North Korean nuclear explosion -- if that’s what it was -- compare with traditional weapons?

A: Estimates by the South Koreans and French indicate the yield of the bomb was equivalent to 500 to 550 tons of TNT. The bombs the United States dropped on Hiroshima and Nagasaki had the force of about 15,000 and 20,000 tons of TNT.

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Q: Does North Korea have the nuclear material to make bombs?

A: The Institute for Science and International Security in Washington says North Korea has enough plutonium for four to 13 weapons, depending on their size.

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Q: Does the test mean that North Korea can launch a nuclear strike against the United States?

A: Probably not. North Korea is generally thought to lack the accurate long-range missiles needed to reach U.S. territory, even in the Pacific Ocean. In July, a test launch of a Taepodong 2 long-range missile ended in failure.

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Q: Then why is there so much concern about the North Koreans’ test announcement?

A: The North Koreans could use the threat of a strike against U.S. allies such as Japan or South Korea for foreign policy gains.

That prospect could lead to an arms race between North Korea and U.S. allies in Asia, which could antagonize China.

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Q: Could North Korea give or sell its nuclear technology and materials to another country or a terrorist group?

A: North Korea dropped out of the Nuclear Nonproliferation Treaty nearly four years ago and no longer is bound by its provisions and oversight. North Korea already has sold missile technology to Iran, among other countries, and Defense Secretary Donald H. Rumsfeld last week said Pyongyang’s government was “an active proliferator.”

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Q: What is being done to stop this?

A: The United States bans the export of military items to North Korea and has restricted financial transactions with Pyongyang. Japan, South Korea and Australia have enacted similar bans. The United States also monitors cargo ships and planes leaving North Korea.

The United Nations in July banned trade in technology that can be used for missiles or weapons of mass destruction. World powers are urging Pyongyang to return to talks with the U.S., China, Russia, South Korea and Japan. Pyongyang insists on bilateral talks with Washington.

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Q: What countries have nuclear weapons?

A: The nations that have declared nuclear weapons are the United States, Russia, China, Britain, France, India, Pakistan and presumably North Korea. Israel is widely thought to have them but has never acknowledged it.