3 Radiation effects and mechanical properties

All in-core components in an SCWR will experience irradiation by α and β particles, neutrons and high-energy photons (γ-rays) resulting in damage at the atomic level in the form of ionization and microstructural degradation due to the development of vacancies, interstitials and voids. These microscopic defects induce changes in physical and mechanical properties such as hardening, ductility, swelling, radiation-induced segregation, and creep, and can increase the risk of cracking. In combination with thermal creep, these changes are a major factor in determining long-term component reliability. This chapter discusses the various forms of radiation damage relevant to SCWR concepts, as well as discussing thermal creep of candidate SCWR materials.