Link between material properties and integrity assessment of NPP components within EU funded projects APAL, INCEFA-SCALE and FRACTESUS

Deep understanding of aging of the most important nuclear power plant (NPP) components and their material degradation on the one hand and development of advanced methods of the assessment of those components’ integrity and lifetime on the other hand is the only way to ensure safe operation of NPPs for long-term operation (LTO). The most significant degradation mechanisms are fatigue and irradiation embrittlement. Within Euratom research and training programme HORIZON 2020, several projects were running in several past years focussed on the research of the above-mentioned degradation mechanisms and on the way of assessing their impact. Three such projects are described in this paper: APAL (Advanced PTS Analysis for LTO) project addresses challenges associated with multidisciplinary character of the pressurised thermal shock (PTS) analyses (both deterministic and probabilistic) and quantification of safety margins, INCEFA-SCALE (INcreasing safety in NPPs by Covering gaps in Environmental Fatigue Assessment – focusing on gaps between laboratory data and component SCALE) aims to improve assessments of fatigue lifetime of nuclear power plant components when subjected to environmentally assisted fatigue (EAF) loading and to provide guidance on the transferability of laboratory scale testing results to component-scale, FRACTESUS (Fracture mechanics testing of irradiated RPV steels by means of sub-sized specimens) aims to determine the effect of specimen size on the fracture toughness properties. Large inter-laboratory testing is included to prove the repeatability and reproducibility of the small-scale testing of fracture toughness properties. Finite element models (FEM) are used to support the experimental results.