Helion is working on a deuterium/helium-3 reactor, which if it works will produce only 6% of its energy as neutron radiation. YCombinator was an investor. They'

Helion is working on a deuterium/helium-3 reactor, which if it works will produce only 6% of its energy as neutron radiation. YCombinator was an investor. They've run six reactors and are building a seventh now for a net power attempt in 2024. There are also at least four companies working on proton-boron fusion, though all but one are very small. (TAE is the exception.)