> Neutron bombardment due to fusion makes hardware radioactive for less than 10 years

Very false. The current design target for fusion reactors is that the materials taken out of the reactor should become "low-level radioactive waste" after being stored for one hundred years.

It is acknowledged however that it is likely that a small fraction of the materials will not satisfy the criteria for "low-level radioactive waste" even after one thousand years.

For example it is extremely difficult to avoid using carbon in the reactor. Besides various kinds of steels used in reactor components there are now some proposals to replace the tungsten used in the plasma-facing surface with some carbides, for increased endurance. Carbon 14 remains radioactive for thousands of years.

There are many commonly used materials for which substitutes must be developed, e.g. new alloys, because otherwise they would produce radioactive isotopes with lifetimes of tens of thousands of years, e.g. there are efforts to develop some stainless steels with chromium and tungsten as a replacement for the normally used steels with chromium and molybdenum, which would generate long-lived radioactive waste.

See e.g. the UK governmental report:

https://assets.publishing.service.gov.uk/media/61ae4caa8fa8f...