The prophet predicts the great flood or inundation. Century 3, Quatrain 13. Referring to nuclear submarine warfare near the millennium. Through lightning in the ship gold and silver are melted, the two captives will devour each other. The greatest one of the city is stretched when the fleet travels underwater.
Plutonium is used to fuel nuclear submarines and the nuclear tipped missiles that they carry.
Nostradamus had no knowledge of plutonium nor of the fact that it has the color of silver. Neither did he know that Plutonium changes to a gold color when exposed to air. During a nuclear explosion, plutonium actually goes through a melting phase for a sub fraction of a second. Lightning is the closest symbol he could use to describe the change of electrical energy state that occurs in a nuclear reaction. The two captives may indicate that the two combatants may have been forced into an unwanted nuclear war and there is mutual destruction.