Radiation materials science is a subfield of materials science which studies the interaction of radiation with matter: a broad subject covering many forms of irradiation and of matter.

Some of the most profound effects of irradiation on materials occur in the core of nuclear power reactors where atoms comprising the structural components are displaced numerous times over the course of their engineering lifetimes. The consequences of radiation to core components includes changes in shape and volume by tens of percent, increases in hardness by factors of five or more, severe reduction in ductility and increased embrittlement, and susceptibility to environmentally induced cracking. For these structures to fulfill their purpose, a firm understanding of the effect of radiation on materials is required in order to account for irradiation effects in design, to mitigate its effect by changing operating conditions, or to serve as a guide for creating new, more radiation-tolerant materials that can better serve their purpose.

The types of radiation that can alter structural materials are neutron radiation, ion beams, electrons (beta particles), and gamma rays. All of these forms of radiation have the capability to displace atoms from their lattice sites, which is the fundamental process that drives the changes in structural metals. The inclusion of ions among the irradiating particles provides a tie-in to other fields and disciplines such as the use of accelerators for the transmutation of nuclear waste, or in the creation of new materials by ion implantation, ion beam mixing, plasma-assisted ion implantation, and ion beam-assisted deposition.

The effect of irradiation on materials is rooted in the initial event in which an energetic projectile strikes a target. While the event is made up of several steps or processes, the primary result is the displacement of an atom from its lattice site. Irradiation displaces an atom from its site, leaving a vacant site behind (a vacancy) and the displaced atom eventually comes to rest in a location that is between lattice sites, becoming an interstitial atom. The vacancy-interstitial pair is central to radiation effects in crystalline solids and is known as a Frenkel pair. The presence of the Frenkel pair and other consequences of irradiation damage determine the physical effects, and with the application of stress, the mechanical effects of irradiation by the occurring of interstitial, phenomena, such as swelling, growth, phase transition, segregation, etc., will be effected. In addition to the atomic displacement, an energetic charged particle moving in a lattice also gives energy to electrons in the system, via the electronic stopping power. This energy transfer can also for high-energy particles produce damage in non-metallic materials, such as ion tracks and fission tracks in minerals.

The radiation damage event is defined as the transfer of energy from an incident projectile to the solid and the resulting distribution of target atoms after completion of the event. This event is composed of several distinct processes:

The result of a radiation damage event is, if the energy given to a lattice atom is above the threshold displacement energy, the creation of a collection of point defects (vacancies and interstitials) and clusters of these defects in the crystal lattice.

The essence of the quantification of radiation damage in solids is the number of displacements per unit volume per unit time ${\displaystyle R}$ :

where ${\displaystyle N}$ is the atom number density, ${\displaystyle E_{max}}$ and ${\displaystyle E_{min}}$ are the maximum and minimum energies of the incoming particle, ${\displaystyle \phi (E_{i})}$ is the energy dependent particle flux, ${\displaystyle T_{max}}$ and ${\displaystyle T_{min}}$ are the maximum and minimum energies transferred in a collision of a particle of energy ${\displaystyle E_{i}}$ and a lattice atom, ${\displaystyle \sigma (E_{i},T)}$ is the cross section for the collision of a particle of energy ${\displaystyle E_{i}}$ that results in a transfer of energy ${\displaystyle T}$ to the struck atom, ${\displaystyle \upsilon (T)}$ is the number of displacements per primary knock-on atom.