1\. Objectives Irradiation hardening is one of the most important aging effects of reactor pressure vessel (RPV) steel in long-term service. A number of studies have indicated that irradiation hardening is mainly caused by irradiation induced defects, such as dislocation loops and precipitates. It is essential to set up microstructure scale models about how these defects be produced and what role they play in hardening, in order to understand and quantify their influence on mechanical behavior of RPV. 2. Methods In this paper, the generation of MnNiSi precipitates in irradiated low-copper RPV steels is simulated by the cluster dynamics (CD) model based on rate theory. Furthermore, we have suggested a modified hardening model based on density and mean size of irradiation induced defects. On this basis, the crystal plasticity finite element method (CPFEM) based on modified crystal plasticity model is used to simulate the effect of MnNiSi precipitates on the mechanical properties of RPV steels. 3. Results For the low-copper RPV steels used in Westinghouse Ringhals PWR Unit 3, we have simulated the evolution of irradiation induced defects by CD. The CD simulation results show the concentration of the point-defects (such as interstitial and vacancy) and defect clusters (such as interstitial loops and precipitates) changed with irradiation dose (0\~7.5\*10 -3 dpa/s), through which we can calculate the mean size of defect clusters. The simulated results of the mean size and density of MnNiSi precipitates is in good agreement with the experimental data (at 6.39\*10 23 n/m 2 , about 0.06 dpa)from Edmondson P D\[1\]. The mean size and density of the precipitates were substituted into our modified hardening model, which uses mean size and density of defects to determine the parameters of crystal plasticity model. The CPFEM simulated result&nbsp;of the yield stress increment of the RPV steels mentioned above is about 185 MPa, which is close to the experimental results from Pål Efsing\[2\]. 4. Conclusions By coupling the cluster dynamics and the crystal plastic finite element method, the irradiation damage simulation of RPV steels can be realized from the microscopic scale to the macroscopic scale, so that the effect of neutron irradiation on RPV steel mechanical properties can be quantitatively interpreted, evaluated and predicted. However, this work still requires large amounts of experimental data about micro damage and macro deterioration of irradiated RPV steels as support. &nbsp; \[\[1\]\] Edmondson P D, Parish C M , Nanstad R K . Using complimentary microscopy methods to examine Ni-Mn-Si-precipitates in highly-irradiated reactor pressure vessel steels\[J\]. Acta Materialia, 2017, 134:31-39. \[\[2\]\] Pål Efsing, Jansson C , Mager T , et al. Analysis of the Ductile-to-Brittle Transition Temperature Shift in a Commercial Power Plant With High Nickel Containing Weld Material\[J\]. Journal of ASTM International, 2007, 4(7):100719-100730.&nbsp;


ICONE Competition - ICONE28-POWER2020-16272: Study on Irradiation Damage of Rpv Steels Based on Coupling Cluster Dynamics and Crystal Plasticity Finite Element Method

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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