Radiation damage
This article deals with Radiation damage due to ionizing radiation on physical objects.
This radiation may take several forms:
Radiation may affect materials and devices in deleterious ways:
Many of the radiation effects on materials are produced by collision cascades and covered by radiation chemistry.
Radiation can have harmful effects on solid materials as it can degrade their properties so that they are no longer mechanically sound. This is of special concern as it can greatly affect their ability to perform in nuclear reactors and is the emphasis of radiation material science, which seeks to mitigate this danger.
As a result of their usage and exposure to radiation, the effects on metals and concrete are particular areas of study. For metals, exposure to radiation can result in radiation hardening which strengthens the material while subsequently embrittling it (lowers toughness, allowing brittle fracture to occur. This occurs as a result of knocking atoms out of their lattice sites through both the initial interaction as well as a resulting cascade of damage, leading to the creation of defects, dislocations (similar to work hardening and precipitation hardening. Grain boundary engineering through thermomechanical processing has been shown to mitigate these effects by changing the fracture mode from intergranular to transgranular (occurring along grain boundaries). This increases the strength of the material, mitigating the embrittling effect of radiation. Radiation can also lead to segregation and diffusion of atoms within materials, leading to phase segregation and voids as well as enhancing the effects of stress corrosion cracking through changes in both the water chemistry and alloy microstructure.
As concrete is used extensively in the construction of nuclear power plants, where it provides structure as well as containing radiation, the effect of radiation on it is also of major interest. During its lifetime, concrete will change properties naturally due to its normal aging process, however nuclear exposure will lead to a loss of mechanical properties due to swelling of the concrete aggregates, and thus damaging the bulk material. For instance, the biological shield of the reactor is frequently composed of Portland cement, where dense aggregates are added in order to decrease the radiation flux through the shield. These aggregates can swell and make the shield mechanically unsound. Numerous studies have shown decreases in both compressive and tensile strength as well as elastic modulus of concrete at around a dosage of around 1019 neutrons per square centimeter. These trends were also shown to exist in reinforced concrete, a composite of both concrete and steel.
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