David Sanderson, a physicist at the Scottish universities' research and reactor centre, says that while this would need heavy investment (and a lot of workers), plutonium can be mixed with waste and vitrified into storable glass blocks, so making it unusable in bombs if any terrorists managed to steal some.

ECONOMIST: The nuclear industry

Frank Barnaby, a respected nuclear physicist and weapons expert, says that a version of the compound with some military application may have been developed in the Soviet Union.

ECONOMIST: Red mercury

"You can see essentially a very high performance cluster the size of a desktop, at the cost of a desktop, " says Nvidia board member Steven Chu, a Nobel Prize-winning physicist and director of the Lawrence Berkeley National Laboratory.

FORBES: Shoot To Kill