Dissemination of IT for the Promotion of Materials Science (DoITPoMS)


Effects of Radiation Damage

The previously discussed changes in microstructure due to radiation damage affect the macroscopic, mechanical properties of the material. These effects happen for a variety of reasons, but are generally less noticeable at higher temperatures as the damage caused by radiation is constantly being annealed out:  at higher temperatures vacancy and interstitial mobility are increased so they are removed from the lattice faster.

The following table gives an overview of the effects observed.

Material Property Effect of Radiation Damage
Yield strength Increases on irradiation, along with a decrease in plastic flow range.
Ultimate tensile strength This also increases on irradiation, but less than the yield strength.
Ductile-brittle transition temperature This marks the transition between a material exhibiting ductile behaviour at higher temperatures and brittle behaviour at lower temperatures. It increases significantly on irradiation, which can present a problem when the reactor vessel cools on shut down when internal pressure within the reactor is still high, and so fracture can occur if this is not taken into account.
Young’s modulus Small increase on irradiation.
Hardness Increase.
High-temperature creep rate Increase during irradiation.
Ductility Decrease.
Stress-rupture strength Decrease.
Density Decrease as the material swells on irradiation.
Impact strength Decrease.
Thermal conductivity Decrease on irradiation since lattice disorder increases, thus increasing phonon scattering.
Electrical conductivity Decrease for similar reasons to thermal conductivity.

The following sketch shows the stress-strain curve for a typical steel and its different form after irradiation.

A stress-strain curve for a stainless steel both before and after irradiation
A stress-strain curve for a stainless steel irradiated or not.