<Li> Li + n → T + α + n unexpectedly contributed additional yield in Castle Bravo, Castle Romeo, and Castle Yankee, the three highest - yield nuclear tests conducted by the U.S. </Li> <P> Either a low - energy projectile is absorbed or a higher energy particle transfers energy to the nucleus, leaving it with too much energy to be fully bound together . On a time scale of about 10 seconds, particles, usually neutrons, are "boiled" off . That is, it remains together until enough energy happens to be concentrated in one neutron to escape the mutual attraction . Charged particles rarely boil off because of the coulomb barrier . The excited quasi-bound nucleus is called a compound nucleus . </P> <Ul> <Li> Low energy (e, e' xn), (γ, xn) (the xn indicating one or more neutrons), where the gamma or virtual gamma energy is near the giant dipole resonance . These increase the need for radiation shielding around electron accelerators . </Li> </Ul> <Li> Low energy (e, e' xn), (γ, xn) (the xn indicating one or more neutrons), where the gamma or virtual gamma energy is near the giant dipole resonance . These increase the need for radiation shielding around electron accelerators . </Li>

Where does the energy from a nuclear reaction come from