1. The fission reaction is released in the form of mass defect energy, that is, Einstein's mass-energy equation e = m * c 2, (e is energy, m is mass, c is the speed of light, and energy is equal to the square of mass multiplied by the speed of light. )

Fission reaction is: heavy nucleus+neutron->; Multiple light nuclear fragments+several neutrons+energy

If the generated neutrons continue to bombard other heavy nuclei to release energy, the generated secondary neutrons can maintain this process, which is a chain reaction. The quality defect is reflected in the mass of all light nuclear fragments+the mass of all secondary neutrons.