alt Hacker News> Neutrons make hardware radioactive
True, but two caveats:
1. Neutron bombardment due to fusion makes hardware radioactive for less than 10 years, which isn't great but does not compare to fission waste;
2. Some fusion processes don't emit neutrons (aneutronic fusion). As I understand it, these processes aren't as efficient, but there is the possibility of a tradeoff between generation of ratioactive waste vs. efficiency.
Replies
Aneutronic fusion is even harder than regular fusion so it's not a realistic solution in any near-term scenario.
Unfortunately is pretty far from "less than 10 years", which I guess you got from the half life of tritium. Tritrium radiocativity, in the form of tritium retained in the plasma facing materials, does contribute in that order of years if done properly, but neutron activation dominates and it's unavoidable. The actual numbers are in the order of hundres of years, still a lot less than fission high level waste, but let's not make unreasonable expectations around fusion, please.
You can find here a good comparison in terms of radiotoxicity vs years after plant shutdown for a few designs in this article [1].
> 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...