The first '' Ivy '' shot , '' Mike '' , was the first successful full-scale test of a multi-megaton thermonuclear weapon ( " hydrogen bomb " ) using the Teller-Ulam design . Unlike later thermonuclear weapons , '' Mike '' used deuterium as its fusion fuel , maintained as a liquid by an expensive and cumbersome cryogenic system . It was detonated on Elugelab Island yielding 10.4 megatons , almost 500 times the yield of the bomb dropped on Nagasaki . Eight megatons of the yield was from fast fission of the uranium tamper , creating massive amounts of radioactive fallout . The detonation left an underwater crater 6,240 ft ( 1.9 km ) wide and 164 ft ( 50 m ) deep where Elugelab Island had been . Following this successful test , the '' Mike '' design was weaponized as the EC-16 , but it was quickly abandoned for solid-fueled designs after the success of the Castle Bravo shot
Castle Bravo
Castle Bravo
Operation Ivy