Evaluation of the erosion on the CFC tiles of the ITER divertor by means of FE calculations

In order to evaluate by finite element (FE) calculations the possibility of erosion instability on the CFC tiles of the vertical target of the ITER divertor an original methodology has been developed using the CAST3M CEA finite element code. The used approach provides a series of steady state calculation steps, the mesh being updated at each step of the iteration in order to take into account the erosion between two steps. Both physical and chemical sputtering together with sublimation have been included in the code to describe the loss of material by the thermal and particle loads envisaged for ITER normal operation regime. This model has been validated by comparison with analytical or other code results and then applied to the ITER divertor vertical target (CFC monoblock geometry). The calculations have pointed out the possibility of some erosion instabilities when a monoblock has a neighbour one with reduced conductivity or with interface defects. However it was shown that when applying normal condition loads (10 MW/m2) for 10,000 s and then off-normal loads (20 MW/m2) for 10 s the total erosion was 1 mm. Based on these first results no modification of the monoblock acceptance criteria is necessary. This way of calculation can be easily transposed in other FE codes and extensively used for checking various ITER operative scenarios.