Integrity assessment of Tokamak-type fusion reactor structures

> For a long time, it was widely assumed that the first wall and blanket structures in fusion reactors could sustain damage levels of around 150–200 dpa. However, the attached recent article reveals that, based on the current data for ferritic/martensitic steels, the actual lifetime could be as low as 15 dpa in a typical Tokamak system. This significantly complicates efforts to design more compact and power-dense reactors—an essential step toward commercial viability."

(dpa = displacements per atom)

From linked paper:

> Using the available database and current empirical prediction methods, we expect the plasma containment structure (FW/B) to probably survive for about one full year of operation under a neutron wall loading of 1.2 MW/m2 and a surface plasma thermal flux of 0.25 MW/m2. These surprising findings suggest that very high fluence properties (100–200 dpa) may not be as significant and that thermal creep damage and rapid reduction in fracture toughness are the main factors controlling failure. Consequently, there is a pressing need to improve the creep strength at temperatures above 500 ◦C and to slow the degradation of the fracture toughness with increasing neutron fluence. Furthermore, it can be projected that for the development of more compact fusion energy sources with neutron wall loadings exceeding 5 MW/m2, new classes of structural materials may be required to achieve economically viable plasma containment structure lifetimes.

(FW/B = First Wall/Blanket)