PSI - Issue 17

Salatiel Pérez Montejo et al. / Procedia Structural Integrity 17 (2019) 123–130 Salatiel Pérez Montejo et al / Structural Integrity Procedia 00 (2019) 000 – 000

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(c)

(d)

Fig. 5. a) Boundary conditions of the submodel at the beltline zone. (b) Finite element mesh of the submodel (c) Finite element mesh at the crack tip (d) Variation of the SIF along the crack front.

5. Results In accordance with the elastic fracture mechanics, the pressure and temperature of operation should not cause that K I becomes equal or greater than K IR at any point of the crack front. In this way, brittle failure is avoided (USNRC, 1981). Equations 8 and 9 were used to determine the temperature-pressure limit curves of the transient conditions considered. It was estimated that minimum temperature of reference is 185°F for the start-up transient and 187 °F for the shut down and cooling transient. In both cases, the pressure of operation is 1000 psi. The results obtained with the analytical procedure by ASME (Table 2) have been compared with those estimated by FEM in Fig. 6.

Fig. 6 Comparison of the minimum reference temperatures determined by the analytical and traditional method vs the results obtained by the FEM applied to the start-up and shut-down transients.

6. Conclusions The minimum temperatures of reference T were obtained for the cases, which were postulated. The results, obtained with the ASME procedure and the FEM, were compared. The values of K I , obtained with the ASME procedure, are more conservative than those obtained with the FEM. When the internal pressure is 1000 psi, the temperature T