Calculation and classification of the radioactive waste inventory in the structural components of a compact ignition fusion machine

The radioactive inventory, decay heat and contact dose rate of certain materials (graphite in the first wall, INCONEL 625 in the vacuum vessel and copper in the magnet) of the IGNITOR-ULT fusion machine are evaluated. The xsdrnpm-s code is used to perform the neutron transport fixed source analysis. The anita-2 code, using updated cross-sections and decay data libraries based on EAF-3 and IRDF90 evaluation files, is used for activation calculations. The fusion neutron source has been normalized to a neutron wall load of 2 MW m −2. The results show that, although the first wall graphite proves to be a relatively benign material, INCONEL 625 in the vacuum vessel and copper in the magnet can become highly radioactive and may need long waiting times before they can be transported to deep geological repositories or recycled. The impact of the variation in the composition of INCONEL 625 on the contact dose has been assessed as a function of the cooling time and its implications for the choice of structural materials in fusion plants are discussed.