Evolution of microstructure and mechanical properties of VVER-1000 RPV steels under re-irradiation

Effect of subgrain structure on the kinetics of phosphorus segregation in grain boundaries

“…the limiting value at ∞ → t is determined by the Langmuir equation: (14) as it should be for the non-limited phosphorus reserve in the grain, but the saturation of the boundary. Further experiments with different initial phosphorus content are needed in order to distinguish the main reason of the experimental curve saturation.…”

“…Kinetic model of phosphorus segregation at relatively low temperatures ~250-350 °C, proposed in the paper, was applied for the low carbon low-alloy vessel steel 15Kh2NMFA-A and weld metal Sv10KhGNMAA (Table 1) used in VVER-1000 reactors [11][12][13][14].…”

“…It should be noted that the surface concentration, measured by AES, is often expressed in fractions of a monolayer (ML) [14]. As a first approximation it can be considered as the atomic concentration b C multiplied by the number of the atomic layers (crystal planes) within the boundary of width δ .…”

Light Water Reactor Sustainability Program Materials Research Pathway Technical Program Plan

“…Long-term service will result in very high accumulations of radiation damage that may be manifested in changes in microstructure such as void formation and different phase fractions than present at lower damage conditions. For example, the formation of ferritic grain structures along previous austenitic grains in 145 dpa irradiated titanium-stabilized stainless steel used in VVER (water-water energetic reactor) designs[21] may increase IASCC susceptibility. Unfortunately, very little IASCC or fracture toughness data exists for high-fluence specimens of austenitic stainless steels (wrought or cast) or weldments within the reactor core.…”