Fission-Fusion-Fission Bomb

The thermonuclear bomb exploded in 1954 was a three-stage weapon. The first stage consisted of a large A-bomb, which acted as a trigger. The second stage was the H-bomb phase resulting from the fusion of deuterium and tritium within the bomb. In the process helium and high-energy neutrons were formed. The third stage resulted from the impact of these high-speed neutrons on the outer jacket of the bomb, which consisted of natural uranium, or uranium-238. No chain reaction was produced, but the fusion neutrons had sufficient energy to cause fission of the uranium nuclei and thus added to the explosive yield and also to the radioactivity of the bomb residues.