At present, the conventional methodology used to assess the structural integrity of RPV does not take into account any possible extension of the initial crack. Nevertheless, in order to improve the methods and obtain a second level of assessment, it could be useful to analyse the possibilities of crack arrest after crack initiation. It is the reason why we have applied the energy approach of elastic-plastic fracture mechanics to the analysis of a cracked disk submitted to a thermal shock inducing very fast crack propagation and crack arrest. This energy approach, originally based on the definition of an energy release rate Gp, for a crack modeled by a notch, has been applied successfully to the analysis of shallow crack and warm pre-stress effects. It gives a good prediction of crack initiation but it cannot predict the distance of crack propagation, at the same time. Nevertheless, if we consider that the critical time of initiation is known, it is then possible to reconsider a sharp tipped crack model and, using energy balance considerations, to predict the distance of crack propagation. In this approach the dynamic effects are not taken into account, the analysis being purely static, which seems to imply a conservative estimation of crack arrest. This simplified static model is presented in the paper including the case of a variable toughness material, which is verified in the study where the material is strongly depending on the temperature. The numerical analysis was performed at EDF-R&D with the Code-Aster, the finite element code of EDF. The mesh was very refined all along the crack propagation area. A non linear thermal finite element analysis was performed in order to determine the thermal field during the crack propagation. Then, the static analysis was performed assuming that the temperature at initiation remains constant during the crack propagation period which is very short. Concerning the values of temperature measured by thermocouples we have found a good agreement between experimental and predicted results. At the time of initiation, t = 7 sec, the KJ value is equal to 36 MPa.m1/2, in agreement with the value predicted by the French Code RCCM. The critical value Gpc of the Gp parameter have been identified at different temperatures. For that it was necessary to interpret different tests on CT specimens submitted to uniform temperature. Assuming that the critical time of initiation is known it was then possible to compute the Gp parameter as a function of the distance of propagation Δl, which can be compared to the Gpc function in order to obtain the distance of crack arrest. The predicted results obtained are in good agreement with the experimental results and less conservative than the results obtained using the RCCM code.

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