PSI - Issue 13

Sergiy Kotrechko / Procedia Structural Integrity 13 (2018) 11–21 Sergiy Kotrechko/ Structural Integrity Procedia 00 (2018) 000–000

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low-copper and low-phosphorus steels. To establish these regularities is one of the challenges for radiation material science. 3. Radiation embrittlement of RPV steels is due to two constituents: ( i ) radiation hardening and ( ii ) radiation induced decrease in brittle strength. The second constituent, as a rule, is not taken into account in existing models, but its contribution to radiation embrittlement is comparable to radiation hardening, and sometimes exceeds it. As follows from the evidence for the weld metal of reactors WWER-1000, neglecting this constituent gives rise to incorrect predictions of the values of limiting fluences for RPVs. 4. A sufficiently deep understanding of the micromechanisms of radiation hardening and, at the same time, the almost complete absence of physical models of radiation-stimulated reduction in brittle strength is a characteristic feature of the current state in the field of strength of RPV materials and radiation material science in general. 5. Existing approaches to RPV life time prediction are phenomenological. When predicting the life time of RPVs, above said doesn’t enable to take into account the features of micromechanisms of their radiation embrittlement during long-term operation and to reduce the conservatism of calculations. 6. The proposed engineering version of the Local approach can be considered as a "bridge" between the physical models of radiation embrittlement and the phenomenological methods of life time prediction. This approach makes it possible to separate the contribution of radiation hardening and radiation-induced reduction in brittle strength to the value of the radiation life time. BEREMIN, F.M., 1983. A local criterion for cleavage fracture of a nuclear pressure vessel steel. Metallurgical Transactions A 14A, 2277–2287. Bergner, F., Ulbricht, A., and Viehrig, H.-W., 2009. Acceleration of irradiation hardening of low-copper reactor pressure vessel steel observed by means of SANS and tensile testing. Philosophical Magazine Letters 89 (12), 795–805. Bordet, S.R., Karstensen, A.D., Knowles, D.M., Wiesner, C.S., 2005. A new statistical local criterion for cleavage fracture in steel. Part I: model presentation. Engineering Fracture Mechanics 72, 435–452. Chaouadi, R., Gerrard, R., 2005. Copper precipitate hardening of irradiated RPV materials and implications on the superposition law and re irradiation kinetics. Journal of Nuclear Materials 345, 65–74. Kotrechko, S.A., Meshkov, Yu., Dlouhý, I., 2001. Computer simulation of effect of grain size distribution on Weibull parameters. Theoretical and Applied Fracture Mechanics 35 (3), 255–260. Kotrechko, S., 2002. Physical Fundamentals of Local Approach to Analysis of Cleavage Fracture, in: Transferability of Fracture Mechanical Characteristic. I. Dlouhy (Ed.), NATO Science Series. Series II, 78, 135–150. Kotrechko, S., Strnadel B., Dlouhy I., 2007. Fracture toughness of cast ferritic steel applying local approach. Theoretical and Applied Fracture Mechanics 47, 171–181. Kotrechko, S., 2013. The key problems of local approach to cleavage fracture. Journal of Theoretical and Applied Mechanics (Warsaw) 51 (1), 75–89. Kotrechko, S., Dubinko, V., Stetsenko, N., Terentyev, D., He, Xinfu, 2015. Temperature dependence of irradiation hardening due to dislocation loops and precipitates in RPV steels and model alloys. Journal of Nuclear Materials 464, 6–15. Kotrechko, S., Mamedov, S., 2016. Multi-scale local approach to cleavage fracture and its applications, 19th European Conference on Fracture (ECF19). - Kazan, Russia, 26-31 Aug 2012. Curran Associates, Inc. 1, 971–982. Kotrechko, S., Gryshchenko, V., Kozak V., Dlouhy I., 2016. Method of Threshold Stress Determination for a Local Approach to Cleavage Fracture. Solid State Phenomena 258, 281–285. Kuleshova, E.A., Gurovich, B.A., Lavrukhina, Z.V., Maltsev, D.A., Fedotova, S.V., Frolov, A.S., Zhuchkov, G.M., 2017. Study of the flux effect nature for VVER-1000 RPV welds with high nickel content. Journal of Nuclear Materials 483, 1–12. Lin, T., Evans, A.G., and Ritchie, R.O., 1986. Statistical analysis of cleavage fracture ahead of sharp cracks and rounded notches. Acta Acknowledgements The present work has been funded by the National Academy of Sciences of Ukraine, grant # 0116U003048. The financial support is gratefully acknowledged. References Balandin Yu. F., Gorynin, I.V., Zvezdin, Yu.I., and Markov, V.G., 1984. “ Structural materials of nuclear power plants ”. Energoatomizdat, Moscow, pp. 280 (in Russian).