U.S. reconnaissance aircraft detect krypton 85 in the atmosphere near the country. WASHINGTON--U.S. spy planes flying near North Korea have detected traces of a radioactive gas emitted during the reprocessing of spent nuclear fuel rods, which could be a possible sign of a secret nuclear facility, sources here said. U.S. intelligence analysts are still trying to determine the significance of finding krypton 85, a radioactive isotope that is a byproduct of reprocessing nuclear fuel rods to extract plutonium, in the atmosphere near North Korea last December. Krypton 85 was also detected in July 2003 when North Korea announced it...