[pfdietz]

Anything exposed to neutrons is not going to be "demonstrated" in the sense of shown to work in an environment of a working production DT reactor. The integrated neutron flux over the lifetime of ITER, assuming it works at all, is just a few percent what would be needed. This will not be sufficient to show the devices or materials are adequate or to conduct necessary reliability growth.

There is the larger issue of whether anything like ITER, with solid surfaces exposed to DT neutron flux, could ever be successful. ITER itself is very far out of the running as a prototype for a competitive source of heat, with volumetric power density of the reactor 400x lower than existing PWRs. A substantial part of that problem is limits on power/area through the exposed surfaces.

[mdprock]

some material in iter are not relevant for future reactors, true. But some yes and will face a fluence that is n order of magnitudes higher than what has been tested in jet, the most powerful tokamak so far. so it's a "half-way" demonstration. in any case materials are not everything, iter will test remote handling, breeding, long pulses, etc etc. we can argue that tokamak are not the right path but at the moment is the most advanced so it is worth pursuing it.