Estimations of erosion fluxes, material deposition and tritium retention in the divertor of ITER

Material mixing effects on erosion/deposition and tritium retention in ITER have been modelled with ERO. It is seen that target lifetime is much less critical than tritium retention. A long-term tritium retention rate of ∼9 mg T/s is obtained, assuming constant beryllium concentration in the background plasma of 0.1% for outer and 1% for inner divertor. Retention in inner is about twice that in outer divertor. Using a TriDyn-based model for mixed layers instead of homogenous material mixing does change the detailed profiles of erosion and redeposition. However, overall tritium retention is almost unchanged. Also, profiles for the beryllium influx along the divertor plates calculated with DivImp have been used for the ERO modelling. The resulting beryllium flux on the targets decreases by factors of 25 (inner) and 55 (outer divertor) compared to constant concentrations used so far. First ERO calculations using these beryllium profiles indicate a reduction of overall tritium retention by a factor of ∼4 (compared to constant beryllium concentrations as used before), mainly due to reduced beryllium deposition.