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Question
What happens to the helium a fusion plant makes?
Fusion produces helium as its 'ash' — an inert, harmless gas that is pumped out. Its energy is captured first by the direct-energy converter.
That fusion's primary by-product is harmless helium is one of its underrated advantages. The in-plant handling is covered on helium ash & exhaust; the broader waste picture on fusion waste & decommissioning.
Questions & answers
What is the 'waste' product of fusion?
Ordinary helium — the same inert, harmless gas in party balloons. When fuel fuses, it leaves helium nuclei behind. There is no toxic or greenhouse gas emitted; the main by-product is a noble gas.
What happens to it in the plant?
The fast helium nuclei first give up their energy to the direct-energy converter and the plasma. Once spent, this helium 'ash' would otherwise dilute the fuel, so it is swept to the divertor and pumped out — and it's even a potentially saleable commodity.
Is the helium radioactive?
No. The helium produced by fusion is stable and non-radioactive. (The reactor's structure becomes mildly activated by neutrons, but that's separate from the helium exhaust.)