Pelindaba is nestled in the African bush, not far from the capital of South Africa. It is where the former Apartheid regime secretly built nuclear weapons. In the 1990s, South Africa chose to disarm. The bombs were dismantled, but the highly enriched uranium, known as HEU - the fuel for the bombs - is still there. South Africa assures the world that Pelindaba is a fortress. But, last year, on the night of Nov. 7, it was the scene of the boldest raid ever attempted on a site holding bomb grade uranium.
"It happened just after one o'clock at night. We heard a sound inside the building," remembers Anton Gerber, who has worked at Pelindaba for 30 years and is the chief of the plant's emergency control center.
He was in the control room when masked men broke in. "There's a crack in the door. And I looked through this and I saw this four armed gunmen entering the passages is coming straight to us in the control room."
Gerber says all four were armed.
The men had breached a 10,000 volt fence, passed security cameras, and walked three quarters of a mile to the control room that monitors alarms and responds to emergencies. Gerber called the security office, just three minutes away.
"I immediately said to them they must come and help us. We're under attack. There's four armed men inside our building. The first guy who stepped into the office, he said to me, 'Why do you phone?' He was shouting at me, 'Why do you phone? Why do you phone?'" Gerber remembers. "And I was still so surprised, you know. My first words to them, 'Is this a joke?'"
The only other employee in the control room was Ria Meiring. "And he grabbed me at my hair and pull me out. And he put a gun to my head while the other three guys were fighting with Anton," she remembers.
But the attack on the control room was just the start. A second group of gunmen, on the other side of the plant, was cutting through the fence and opened fire on a guard.
Asked if he thinks the gunmen were after the HEU, Matthew Bunn of Harvard's Kennedy School of Government tells correspondent Scott Pelley, "That's certainly the most valuable single thing that's at that site."
Bunn has studied the attack and has written a classified report for the government on atomic security. He says highly enriched uranium is extremely difficult to make, and would be worth millions of dollars on the black market. And if terrorists get a hold of it, it would not be hard to build a crude atomic bomb. "Making a nuclear bomb with highly enriched uranium basically involves slamming two pieces together at high speed. That's really all there is to it," he explains.
Asked how much highly enriched uranium a terrorist group would need to build a weapon, Bunn says, "The amount of highly enriched uranium metal would basically fit into the cans of a six pack."
And handling the material, according to Bunn, isn't very dangerous. "Unfortunately not. Highly enriched uranium is only very weakly radioactive. You can handle it with your hands."
Pelindaba holds more than a thousand pounds of HEU, and it uses some of it to make medical products. South Africa calls the plant is a "national key point," a facility with the highest security.
"This is the first time that this has ever happened on site," says Ari Van Der Bijl, the general manager.
Van Der Bijl brought 60 Minutes to the place where the gunmen got through the electric fence.