U U Sb Nb n ( . ) Still another example is U Xe Sr n ( . ) The fragment nuclei produced in fission are highly neutron-rich and unstable. They are radioactive and emit beta particles in succession until each reaches a stable end product.
The energy released (the Q value ) in the fission reaction of nuclei like uranium is of the order of MeV per fissioning nucleus. This is estimated as follows: Let us take a nucleus with A = breaking into two fragments each of A = . Then E bn for A = nucleus is about . MeV, E bn for the two A = fragment nuclei is about .
MeV. Gain in binding energy for nucleon is about . MeV. Hence the total gain in binding energy is × .
or MeV The disintegration energy in fission events first appears as the kinetic energy of the fragments and neutrons. Eventually it is transferred to the surrounding matter appearing as heat. The source of energy in nuclear reactors, which produce electricity, is nuclear fission. The enormous energy released in an atom bomb comes from uncontrolled nuclear fission.
We discuss some details in the next section how a nuclear reactor functions. . . Nuclear reactor When U undergoes a fission after bombarded by a neutron, it also releases an extra neutron.
This extra neutron is then available for initiating fission of another U nucleus. In fact, on an average, 2½ neutrons per fission of uranium nucleus are released. The fact that more neutrons are produced in fission than are consumed raises the possibility of a chain reaction with each neutron that is produced triggering another fission.