Mahmoud Ahmadinejad tells his atomic energy chief to boost uranium enrichment from 3.5% to 20% as talks over a nuclear-fuel exchange sputter. Iran's energy chief says it's simply an 'alert.' In a possible move to deflect attention from Iran's political woes, President Mahmoud Ahmadinejad on Sunday ordered the nation's atomic energy agency to begin enriching uranium from 3.5% to 20% purity to serve as fuel for a Tehran medical reactor.