Igor Bolshinsky

Over the last three years, two U.S. nuclear weapons experts have quietly crisscrossed the globe, racing to secure bomb-grade uranium before terrorists can lay their hands on a single kilogram. Andrew Bieniawski, 40, a boyish-looking immigrant from South Africa, has led the effort by the National Nuclear Security Administration, slogging from reactor to reactor trying to persuade foreign scientists and government officials to give up their highly enriched uranium fuel.

Over the last three years, two U.S. nuclear weapons experts have quietly crisscrossed the globe, racing to secure bomb-grade uranium before terrorists can lay their hands on a single kilogram. Andrew Bieniawski, 40, a boyish-looking immigrant from South Africa, has led the effort by the National Nuclear Security Administration, slogging from reactor to reactor trying to persuade foreign scientists and government officials to give up their highly enriched uranium fuel.