PSI - Issue 37

M. Annor-Nyarko et al. / Procedia Structural Integrity 37 (2022) 225–232 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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2. RPV model and thermo-mechanical properties The geometrical vessel model used for this study consist of one-half symmetry of a typical two-loop PWR RPV, as shown in Fig.1. The main parameters of the referenced reactor are presented in Table 1. The inner diameter (ID) of the RPV, wall thickness, and inlet nozzle ID are 3.374 m, 0.170 m and 0.70 m respectively. Also, t he RPV material is made of SA508 Class 3 steel with thermo-mechanical properties listed in Table 2 (He and Isozaki, 2000). The mean linear thermal expansion coefficients used for the thermo-mechanical stress calculations were converted to the stress free reference temperature of 289 o C based on the conversion method described in (Niffenegger and Reichlin, 2012). In addition, the yield strength of vessel material at room temperature, density and Poisson’s ratio are 450 MPa, 7600 kgm -3 and 0.3 respectively as reported in (He and Isozaki, 2000; Yu et al., 2015). The RPV model is pre-processed and meshed using finely discretized hexahedral elements in hypermesh software and Symmetricity boundary conditions are applied for the thermo-mechanical analysis (Altair, 2014)

Fig.1. (a) Geometry of RPV with an inlet nozzle (b) Finite element mesh of the RPV model

Table 1. The main parameters of referenced NPP

Parameters Reactor type

value

2 -loop PWR

Design pressure

17.2 MPa 15.2 MPa 21.5 MPa 288.8 o C 315.2 o C 30 years 350 o C

Normal operating pressure Hydrostatic test pressure

Design temperature

Normal operating inlet temperature Normal operating outlet temperature

Design life

Table 2. Thermo-mechanical properties of the RPV material

T( o C)

λ (W/m o C)

E (GPa)

α (10 -6 1/ o C)

C (10 6 J/ m 3 o C)

50

38.3 38.8 38.8 38.6 38.1 37.5 36.8

191 187 184 181 178 174 171

13.8 14.2 14.7 15.5 17.5 18.6 18.6

465.8 489.0 508.4 527.7 545.8 567.7 588.4

100 150 200 250 300 350