In nuclear physics, a fission reaction that is maintained because neutrons released by the splitting of some atomic nuclei themselves go on to split others, releasing even more neutrons. Such a reaction can be controlled (as in a nuclear reactor) by using moderators to absorb excess neutrons. Uncontrolled, a chain reaction produces a nuclear explosion (as in an atom bomb).
The emblem was added to distinguish the flag from that of Italy. The design is based on the French tricolour. The colours are those of the Mexican liberation army. Effective date: 23 November 1968.