PSI - Issue 59

Yaroslav Dubyk et al. / Procedia Structural Integrity 59 (2024) 36–42 Dubyk and Zvirko/ Structural Integrity Procedia 00 (2019) 000 – 000

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Table 1. Results of the FE analysis. An example of a column heading

Dimensions

Without corrosion

With corrosion

Residual wall thickness Radial displacements

[%]

43.47

31.05

[mm] [MPa]

10.505 585.48

10.494 584.24

Equivalent stress

Equivalent plastic strain Equivalent creep strain

[mm/mm] [mm/mm]

0.003525 0.033664

0.003525 0.030359

Analyzing Table 1 and Fig. 3, Fig. 4 we may see that stress fields and maximum stress values are practically unaffected; this is due to the fact that RPV wall carrying capacity is determined by the „cold zone‟, see Fig. 2, which is the same for both type of analysis. Corrosion affect only in reduction of „hi gh- temperature zone‟, in which material is hardly damaged and practically can‟t withstand any load. Another important parameter for WWER -440 IVMR application are radial displacements, since they will determine the gap for external coolant flow, they are practical the same for both types of calculations (see Table 1). Also, from Fig. 4, we can see that equivalent creep deformations are lower due to the excluding from analysis zones of accelerating creep effects.

Fig. 4. Maximum stress and displacements over time left - calculations without corrosion, right – calculations with corrosion.

4. Conclusions This article presents a revision of IVMR application for WWER-440 with consideration of corrosion process between corium and RPV wall. The corrosion equation is taken from the results of EU METCOR project, with a limiting temperature of 1090 ℃ . The results show that corrosion influences the residual wall thickness, which is approximately 10-15% thinner than without corrosion consideration. Detailed FE stress-strain analysis with consideration of creep and plasticity showed that maximum values of stresses are unaffected, and the wall still maintain the loading. This is due fact, that loading is mainly held by the cold part of the wall thickness, which is the same in both calculations. Due to the corrosion elements from the „high - temperature zone‟ are excluded(killed), this zone has no practically carrying capacity, and the material in this zone is hardly damaged. Thus, for application the IVMR strategy to SMRs, it is recommended to include corrosion considerations in sensitivity study, or in the base case estimation if the residual wall thickness is concerned.