Krypton clue to North Korean nuclear progress [New Scientist]
Suspicions that North Korea has begun to extract plutonium for making nuclear bombs have been heightened by US claims that it has detected a tell-tale radioactive gas.
But speculation that the country may have secretly built a second plutonium plant is being treated with caution by experts. "Recent experience suggests we should reserve judgement until we get proof," says Jon Wolfsthal, a former US weapons inspector in North Korea.
On Sunday, reports quoted US government officials as saying that elevated levels of krypton-85 had been discovered in the air above the North Korean border. This is a gas with a half-life of 10.7 years that is created along with plutonium by the fission of uranium fuel in a reactor. The fuel is reprocessed to separate out the plutonium by dissolving it in acid, but this also releases the krypton-85.
