That was fission. What about fusion, then? Is it even more powerful? Let us consider the most energetic and easiest to achieve fusion reaction, that of deuterium with tritium. Reacting the two heavy isotopes of hydrogen produces one neutron, one alpha particle (which is basically a helium nucleus) and 17.6 MeV of energy, of which 14.1 MeV go with the neutron and 3.52 MeV with the alpha particle. One sees immediately that, considering the energy released per reacting nucleus, fusion is actually much less energetic than fission! The balance swings back to the side of fusion, when one instead considers the amount of energy released per unit mass. Recalling that the atomic weight of the chain-reacting isotope of uranium is 235, and that of weapon-grade plutonium is 239, whereas the atomic weight of the resonant state briefly formed by the interacting nuclei of deuterium and tritium is 5v we find that the nuclear energy released per nucleonvi is four to five times higher in the fusion cases. Higher, but certainly not in the range of a thousand times higher! Furthermore, fourth-fifth of the fusion energy goes into the neutron channel in the case of D-T fusion, whereas most of the energy of a fission reaction goes into the kinetic energy of the two electrically charged daughter nuclei, which, together with the instantaneous X-rays, drive effectively the propagation of the fireball of a nuclear explosion. The escaping neutron from a deuterium-tritium fusion reaction, on the other hand, cannot directly produce heat and blast effects. This brings down the militarily directly useful energy release per nucleon of D-T fusion at precisely about the same level as that of fission, but the overall energy release per reaction, and per nucleus, is much higher in the case of fission: over 10 times in absolute terms, and some 50 times higher if one counts up only the energy released through charge particles and electromagnetic energy, the channels which can drive heat and blast effects from an explosion.
