Some solar systems have 2 or even 3 fusion reactors. :) The answer to your question depends on the characteristics of the technology. There are many proposed v

Some solar systems have 2 or even 3 fusion reactors. :) The answer to your question depends on the characteristics of the technology. There are many proposed variations (eg the traditional H-H including heavier isotopes, He₃, pB). For fuels, deuterium is abundant in the environment environment so isn't an issue. Tritium decays quickly. This is a fairly common theme with lighter elements. U₂₃₅ on the other hand is extremely problematic for being both a heavy metal, long-lived and radioactive. But I'm not yet convinced we'll actually have commercial fusion power. Aneutronic variants aside, neutron embrittlement and the energy loss from neutrons are significant unsolved problems. Even with powerful magnets, containing a fluid at 100M Kelvin is a significant problems, inherently so because of turbulence. I hope relatively cheap fusion power is in our future but there's no clear path forward yet. None of these have particularly problematic byproducts.