TEHRAN, Iran - Iran has doubled its capacity to enrich uranium by successfully executing the process with a second network of centrifuges, a semiofficial news agency reported Friday, sending a defiant new message to the U.N. Security Council. Council members are working on a draft resolution that would impose limited sanctions on the Islamic republic because of its refusal to cease enrichment, a process that can produce fuel for a civilian nuclear reactor or fissile material for a warhead. The Iranian Students News Agency quoted an anonymous official as saying Iran has successfully begun injecting gas into a second network...