3. Main degradation modes under irradiation

Irradiation is one of the specific constraints on materials used in nuclear reactors.

Under the term irradiation, we can distinguish three types of interaction between incident particles (neutrons, electrons, α-particles, ions, fission fragments or γ-rays) and a material (figure 1 ):

• inelastic interactions, in which incident particles penetrating the material interact with electrons (inelastic shocks causing electronic excitations and ionizations of the shocked atoms);

• elastic interactions, in which incident particles entering the material interact with the nuclei (elastic shocks with conservation of kinetic energy);