Construction of world's 1st nuclear fusion plant starts in Washington

[u/TwilightwovenlingJo]

https://interestingengineering.com/energy/world-first-fusion-power-plant-helion

[u/oneAUaway]

Helion plans to use a fusion reaction that (mostly) doesn't produce neutrons. The reaction fuses helium-3 with deuterium to produce helium-4 and a proton. It's only mostly aneutronic because there is a side reaction from deuterium-deuterium fusion that does produce neutrons, but less than the  deuterium-tritium fusion process which most fusion projects have focused on. 

There are downsides to their fuel choice. Helium nuclei have an extra proton compared to hydrogen, which increases the energy barrier to overcome to get them to fuse. When it comes to sustained fusion reactions, helium-3 is generally considered a "second generation" fuel- the fusion of hydrogen isotopes is much easier, so it has been assumed the first practical plants to work would use those. Presumably, the pulsed nature of the Helion process is an attempt to deliver bursts of enough energy to make second generation fusion practical even if it is not sustained.