PSI - Issue 28

Casper Versteylen et al. / Procedia Structural Integrity 28 (2020) 1918–1929 Versteylen/ Structural Integrity Procedia 00 (2020) 000–000

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nozzle through which the cooling water is supplied. The inner wall functions as core support barrel and also ensures cold water flows down, see Figure 2a. More details on the geometry can be found in previous analyses by Uitslag Doolaard et al. (2019). The geometry modelled consists of a quarter of the RPV, which is constraint on the symmetry edges and on the bottom surface by restricting displacement and by applying a pressure on the inner RPV wall, see Fig. 2. The CFD analyses on the fluid flow and heat exchange of fluid to the surface of the RPV provided the temperatures used in the FEM analyses. The thermal loading is very complicated due to the process of hot and cold fluid mixing Uitslag-Doolaard et al. (2019).

Fig. 2: The constraints applied to the model, with displacements set to zero in x-direction of the local coordinate system and a pressure of 15 MPa applied to the inner RPV wall surface.

The postulated cracks present in the model of the RPV have radii which are prescribed by ASME (2016). FEM analyses were performed for the standard ASME sized cracks, 10% larger cracks, 10% smaller cracks, cracks with a different aspect ratio and standard cracks with a different grade of pressure vessel steel, see Table 1. The postulated cracks are defined in axial direction on the inside of the pressure vessel, where the principal stress concentration is highest. The RPV suffers from hoop stress due to the effects of pressure and thermal stresses due to the cooling water. The RPV suffers from irradiation embrittlement related to the dpa. Based on these factor 6 locations were selected where to analyze the LOCA event on a postulated crack, see Figure 3. Two columns of cracks are defined; the left section containing crack 4, 5, and 6 and the center section with respect to the nozzle containing cracks 7, 8, and 9. The cracks semi-elliptical cracks, the geometry of which and the meshing procedure is standard in ANSYS® Mechanical, Release 19.2. The mesh was refined around the crack tip until mesh convergence was reached.