fissionable

“But it is a weapon for aggressors, and the elements of surprise and of terror are as intrinsic to it as are the fissionable nuclei,” Oppenheimer writes.

Oppenheimer once called the atomic bomb “a weapon for aggressors” wherein “the elements of surprise and terror are as intrinsic to it as are the fissionable nuclei.”

When the pieces came together, they created a supercritical mass of fissionable, explosive uranium.

Such a big presence would be needed to secure and remove WMD any materials with "enough fissionable plutonium and uranium by build up to 75 weapons by 2020," the report said.

Iran waited a year before beginning to break limits of the accord, each move slightly narrowing the estimated year it would need to have enough fissionable material for a nuclear weapon.