Modelling of tritium retention and target lifetime of the ITER divertor using the ERO code

Material erosion, transport and deposition in the divertor of ITER are modelled with the Monte-Carlo impurity transport code ERO taking into account chemical erosion, physical sputtering, enhanced chemical erosion of redeposited carbon and a beryllium influx from main chamber erosion. The continuous deposition of beryllium leads to reduced carbon erosion along the divertor plates with increasing exposure time. With 1% beryllium in the edge plasma an upper value of the long-term tritium retention rate can be estimated to about 15.9 mg T/s. For 0.1% beryllium this number decreases to about 6.4 mg T/s. These numbers do not change significantly with the sticking assumption for hydrocarbons. The erosion of the divertor plates is less critical. Maximal erosion rates of 0.4 nm/s with 1% beryllium and 1.8 nm/s with 0.1% beryllium occur at the outer target. Erosion due to transient heat loads is not yet included in the modelling.