Understanding thermally induced embrittlement in low copper RPV steels utilising atom probe tomography

Embrittlement is the primary factor limiting the lifetime of reactor pressure vessels (RPVs). This literature review provides an overview of the causes of hardening and non-hardening embrittlement in RPV steels, with a specific emphasis on precipitation hardening caused by manganese-nickel rich precipitates (MNPs) in thermally aged RPV steels. Several models used to describe the hardening mechanism are discussed. The role of atom probe tomography (APT) in investigating solute clustering in RPV steels is also discussed. The characterisation of nanoscale clusters is enabled by APT's unique combination of high mass and 3D spatial resolution. This technique, its limitations and the relevant statistical analysis methods available are reviewed.