The irradiation behavior of graphite is essential for its applications in the nuclear industry.However,the behavioral differences of graphite remain obscure because of the very limited comprehension of its microstruct...The irradiation behavior of graphite is essential for its applications in the nuclear industry.However,the behavioral differences of graphite remain obscure because of the very limited comprehension of its microstructural differences.One typical structure,the quinoline-insoluble(QI)particle,was investigated using IG-110 and NBG-18 graphite.After irradiation,the QI particles on the polished surface were proven to become hillocks,which were easily identifiable via scanning electron microscopy(SEM).Thus,a method that combined ion irradiation and SEM characterization was proposed to study the distribution and concentration of QI particles in graphite.During irradiation,the QI particles were found to evolve into densified spheres,which were weakly bonded with the surrounding graphite structures,thereby indicating that the densification of QI particles did not evidently contribute to graphite dimensional shrinkage.A much higher concentration of QI particles in NBG-18 than IG-110,which was suggested to be responsible for the smaller maximum dimensional shrinkage of former over the latter during irradiation,was characterized.展开更多
This paper intensively explores the critical issues related to the quantitative and accurate evaluations of FCG behavior in the early stage,macro fatigue fracture toughness,and the critical crack size for damage toler...This paper intensively explores the critical issues related to the quantitative and accurate evaluations of FCG behavior in the early stage,macro fatigue fracture toughness,and the critical crack size for damage tolerance in nuclear graphite.To address these issues,scale-span FCG tests were carried out using two typical specimens,CT and SEM in-situ specimens.These results indicate that the FCG threshold and the effective FCG length have a significant correlation with the modified maximum loop stress theory for a mixed I/II mode.In particular,the effective FCG length(a_(eq))and the applied stress threshold of polycrystalline graphite are important parameters for fatigue damage tolerance design in engineering application.The influencing factors of ΔK_(th,eq) and a_(eq) were discussed in detail using the mixed I/II mode,respectively.In addition,the scattered values of ΔK_(IC) for this graphite can be quantitatively estimated using the Weibull distribution equation.The predicated parameters and experimental results demonstrate a strong correlation.展开更多
基金This work was supported by Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2019262)the National Natural Science Foundation of China(Nos.11505265,11805256,11805261).
文摘The irradiation behavior of graphite is essential for its applications in the nuclear industry.However,the behavioral differences of graphite remain obscure because of the very limited comprehension of its microstructural differences.One typical structure,the quinoline-insoluble(QI)particle,was investigated using IG-110 and NBG-18 graphite.After irradiation,the QI particles on the polished surface were proven to become hillocks,which were easily identifiable via scanning electron microscopy(SEM).Thus,a method that combined ion irradiation and SEM characterization was proposed to study the distribution and concentration of QI particles in graphite.During irradiation,the QI particles were found to evolve into densified spheres,which were weakly bonded with the surrounding graphite structures,thereby indicating that the densification of QI particles did not evidently contribute to graphite dimensional shrinkage.A much higher concentration of QI particles in NBG-18 than IG-110,which was suggested to be responsible for the smaller maximum dimensional shrinkage of former over the latter during irradiation,was characterized.
基金supported by the National S&T Major Project(Grant No.ZX06901)Additional funding was provided by the National Natural Science Foundation of China(Grant Nos.11572170 and 11872225).
文摘This paper intensively explores the critical issues related to the quantitative and accurate evaluations of FCG behavior in the early stage,macro fatigue fracture toughness,and the critical crack size for damage tolerance in nuclear graphite.To address these issues,scale-span FCG tests were carried out using two typical specimens,CT and SEM in-situ specimens.These results indicate that the FCG threshold and the effective FCG length have a significant correlation with the modified maximum loop stress theory for a mixed I/II mode.In particular,the effective FCG length(a_(eq))and the applied stress threshold of polycrystalline graphite are important parameters for fatigue damage tolerance design in engineering application.The influencing factors of ΔK_(th,eq) and a_(eq) were discussed in detail using the mixed I/II mode,respectively.In addition,the scattered values of ΔK_(IC) for this graphite can be quantitatively estimated using the Weibull distribution equation.The predicated parameters and experimental results demonstrate a strong correlation.
