NUCLEAR REACTIONS

Nuclear Fusion:

If light nuclei are forced together, they will fuse with a yield of energy because the mass of the combination will be less than the sum of the masses of the individual nuclei. If the combined nuclear mass is less than that of iron at the peak of the binding energy curve, then the nuclear physics will be more tightly bound than they were in the lighter nuclei, and that decrease in mass comes off in the form of energy according to the einstein relationship. For elements heavier than iron, fission will yield energy.

For potential nuclear energy sources for the Earth, the dueterium-tritium fusion reaction contained by some kind of magnetic-confident seems the most likely path. However, for the fueling of the stars, other fusion reactions will dominate.

NUCLEAR FISSION:

Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts (lighter nuclei). The fission process often produces free electrons and photons(in the form of gamma rays), and releases a large amount of energy. In nuclear physics, nuclear fission is either a nuclear reaction or a radioactive decay process. The case of decay process is called spontaneous fission and it is very rare process. In this section, the neutron-induced nuclear fission, the process of the greatest practical importance in reactor physics, will be discussed.

Principles of Nuclear Fission

In general, the neutron-induced fission reaction is the reaction, in which the incodent neutron enters the heavy target nucleus (fissionable nucleus), forming a compound nucleus that is excited to such a high energy level (Eexcitation > Ecritical) that the nucleus splits into two large fission fragments. A large amount of energy is released in the form of radiation and fragment kinetic energy. Moreover and what is crucial, the fission process may produce 2, 3 or more free neutrons and these neutrons can trigger further fission and a chain reaction can take place. In order to understand the process of fission, we must understand processes, that occur inside the nucleus to be fissioned. At first, the nuclear binding energy must be defined.