I'm trying to write a paper arguing for why we should spend more money on nuclear fusion research. I keep reading that "nuclear fusion produces no long lived radioactive waste", but when I looked up why this is the only good source I could find was Quora, clearly not something I can really cite. So, I was hoping someone here could explain it to me, and hopefully also leave their sources so I could use them as well.

  • $\begingroup$ How about looking at a fusion site iter.org/mach/safety $\endgroup$
    – anna v
    Mar 7, 2021 at 16:55
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    $\begingroup$ Fusion radiates its container with neutrons, producing a radioactive containment vessel. The half life of the radioactive materials depends on what materials the containment vessel is constructed with. I'm not well versed in fusion, but I'm sure a fusion expert on this forum could give you good data on what these half-lives are. $\endgroup$ Mar 7, 2021 at 17:23
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    $\begingroup$ This is not a good question to ask here. You are asking us to do your homework for you about supporting and sourcing a political argument. $\endgroup$ Mar 7, 2021 at 18:04
  • $\begingroup$ One problem is that "waste" is a contextually sensitive and politically defined term, not a physics term. If you mean "radioactive matter" then both fission and fusion produce it, but they are of different kinds. $\endgroup$ Mar 7, 2021 at 18:10
  • $\begingroup$ Start at wikipedia, and a quick overview can be found by reading the ~15 sentences thoughout that contain the word "radioactive". In short, fusion waste is radioactive from neutron bombardment, but the radioactivity has a much shorter half life than fission waste making it much more manageable. $\endgroup$
    – tom10
    Mar 7, 2021 at 19:20

1 Answer 1


Fusion does create highly radioactive waste, in the following way.

The main power output of a fusion reactor comes in the form of high-speed neutrons. These then give up their kinetic energy in collisions with the so-called first wall inside the reactor, which heats up. Heat exchange piping then carries away this heat, which is used to boil water and spin a turbogenerator set.

That piping is made from stainless steel superalloys, which are exposed to an intense flux of neutrons while the reactor is running. When the chrome, nickel and iron in the stainless happen to capture any of those neutrons, they can get transmuted into unstable isotopes which then undergo radioactive decay. Some of these decay products are violently radioactive and remain so for years.

(As for the first wall "blanket" itself, refractory ceramics are favored, but their exact compositions have not been completely worked out so the amount of radioactivity they will produce by getting activated by neutron capture isn't well-known yet.)


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