Formation And Evolution Of Clusters In RPV Steel Under Proton Irradiation

Reactor pressure vessel?RPV?is the only non-replaceable nuclear safety first-class device in a nuclear power plant.Its service life directly determines the service life of the entire nuclear power plant.The microstructure of the RPV steel gradually changes under irradiation.Large number of solute clusters form,accelerating the embrittlement of RPV steels,which remarkably affects the service life of the RPV.Investigation on the formation and evolution of solute clusters in low carbon RPV steel under irradiation is not only an urgent need on the project,but also has important scientific value for improving the theory of irradiation damage.In this paper,proton irradiation with dose of 0.0409dpa,0.0798dpa,0.0937dpa,0.116dpa,0.154dpa and 0.273dpa respectively was perfomed on a low-carbon RPV steel at 292°C with proton energy of 250keV.Transmission electron microscopy?TEM?technology and scanning transmission electron microscopy?STEM?technology were conducted to systematically investgate the formation and evolution of dislocation loops and solute clusters.Nano hardness of the proton irradiated low-carbon RPV steel was also measured by nanometer indentation apparatus with continuous stiffness testing technology.The results indicated that the number density of dislocation loops decreased with the increase of irradiation dose and the relationship is N=7.7?^-0.04.The number density of dislocation loops decreased from 9.3×10²¹ m^-33 to 8.1×10²11 m^-33 when the irradiation dose increased from 0.0409dpa to 0.273dpa.The relationship between average radius of dislocation loops and irradiation dose also meets power function of d=12.6?^0.17.The hardness was 4.8Gpa under 0.154dpa irradiation compared to 4.5Gpa under 0.0409dpa irradiation.Dislocation loops with the bourges vector of<100>type were introduced under proton irradiation,which was favorable positions for solute clusters nucleation.The Mn-Ni-Si-rich clusters,Mn-rich clusters as well as Mn-Ni-rich clusters were observed in the RPV steel both under 0.116dpa and0.154dpa irradiation fluence.With the increase of irradiation dose,the density of Mn-Ni clusters decreases while the density of Mn-Ni-Si clusters increases,suggesting an evolution from Mn-Ni clusters to Mn-Ni-Si clusters...