| The major limiting step is acquisition of the fissile material either enriched uranium or plutonium. |
| It also is the toxic and radioactive byproduct of enriched uranium, the fissile material in nuclear weapons. |
| If they acquire sufficient weapons-grade fissile material from abroad, they could make a nuclear weapon within a year. |
| For example, fissile slates tend to yield much flatter particles than massive granites. |
| No natural reactors exist today, as the relative density of fissile uranium has now decayed below that needed for a sustainable reaction. |
| A nuclear weapon using plutonium requires approximately six kilograms of fissile material. |
