Rob Edwards writes in New Scientist magazine that the U.S. can tell North Korea is extracting plutonium from nuclear power plant fuel rods and using it to make bombs, because satellites are detecting signs of the radioactive gas krypton-85 in the area. But now that our claim that Iraq bought uranium from Africa has been proven false, will anyone believe us?

Krypton-85 is a gas with a half-life of 10.7 years that is created along with plutonium during the fission of uranium fuel in a reactor. When the nuclear fuel is reprocessed to separate out the plutonium, krypton-85 is released. Former weapons inspector Jon Wolfsthal says the detection of krypton-85 is a reliable sign that plutonium has been extracted, but it doesn’t reveal where, when or how much. He says, “It’s a red flag, not a yardstick.”

He thinks it’s even possible that the North Koreans are deliberately releasing krypton-85 gas captured from earlier reprocessing in order to make us think they’re making greater progress in bomb-making than they really are. A previous U.S. administration gave them aid in return for abandoning their nuclear weapons program, and the desperately poor country may want to get more aid this way.

Gary Samore, of the International Institute for Strategic Studies, says there are also reprocessing plants in China, Russia and Japan, and the gas could be coming from one of these.

Can we expect other countries to trust us? Here’s why not.

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