This article provides a comprehensive overview of the STRUMAT-LTO project. Embrittlement of the reactor pressure vessel (RPV) due to neutron irradiation and high temperature conditions impose critical challenges for long-term operation (LTO) of pressurized water reactors (PWRs). Significant amount of past research conducted on RPV ageing phenomena has helped to enhance the understanding of the flux effect and the impact of chemical/microstructural heterogeneities on RPV embrittlement. Nonetheless, several unresolved questions regarding RPV embrittlement persist, such as the conflicting viewpoints on the underlying mechanisms that lead to accelerated embrittlement at high fluence conditions in certain low-copper (Cu) RPV steels and the synergistic
effect between nickel, manganese, and silicon (Ni-Mn-Si). Also, the accuracy of embrittlement trend curves (ETCs) for LTO beyond 60 years and the applicability of the master curve approach at high fluences for small/sub-sized specimens require further study. The aim of the STRUMAT-LTO is to address the above-mentioned scientific gaps in RPV embrittlement by employing a unique set of RPV steel specimens constituting systematic variations in Ni, Mn, and Si content, which are irradiated to high fluences resembling reactor operation beyond 60 years within the LYRA-10 experiment at high flux reactor (HFR) in Petten. The STRUMAT-LTO project has received funding from the Euratom research and training programme 2019–2020 under grant agreement
n◦945272. The project has a duration of 48 months.