Nuclear Reactor Physics - Nuclear Reactions

In a nuclear reactor, neutrons generate nuclear reactions. The neutron's neutrality makes it insensitive to the coulombic barrier induced by the presence of the atom's charges (protons and electrons) and, consequently, makes it a preferred projectile for interacting with the atom's nucleus to cause, for example, the fission of a nucleus with a high atomic mass. Fission is not the only nuclear reaction to be considered in a nuclear reactor. In fact, there are several types of nuclear reaction, and their occurrence varies from one target isotope species to another. In a reactor, they take place not only in the fuel, but also in all core structures and those beyond the core.

Other types of nuclear device involve nuclear reactions: thermonuclear fusion machines (using magnetic and inertial confinement) in which light elements interact, and particle gas pedals that can trigger spallation reactions.

Knowledge of these nuclear reactions is essential for understanding the operation of a nuclear reactor and all the nuclear phenomena associated with the fuel cycle, using appropriate physico-mathematical models.

This article begins by describing the main general characteristics of neutron-induced nuclear reactions: phenomenology, energetics, cross sections... The second part deals with specific nuclear reactions, in particular fission. Finally, a brief overview is given of thermonuclear fusion and spallation reactions.

This presentation is a natural sequel to the article Reactor physics – The basics of nuclear physics [BN 3 010] devoted to the structure of the atomic nucleus and its stability, using all the concepts introduced. The reader can then refer to the article Reactor physics – Nuclear data processing [BN 3 012] which complements [BN 3 010] and the present article, with a presentation...