In recent weeks, Iran has dramatically escalated efforts to seal off its cache of near bomb-grade uranium, deliberately collapsing tunnels and booby-trapping entrances with explosive mines, according to five sources familiar with US intelligence. Getting to the roughly half-a-ton of highly-enriched uranium is now far more difficult, dangerous and time-consuming than it already was just … The post CNN Exclusive: Iran sealed uranium cache and placed mines amid fears of US operation to seize material appeared first on Egypt Independent .