NuScale is publicly traded. You can buy shares, the ticker is SMR.
The majority owner (about 60%) in NuScale is Fluor Corporation [1], another publicly traded company (FLR). The top 10 Fluor owners are mutual funds, such as BlackRock, Vanguard and Fidelity [2] . If your 401(k) is managed by one of these funds, chances are you own shares in FLR too.
I don't see how Bill Gates is involved in NuScale.
[1] https://newsroom.nuscalepower.com/press-releases/news-detail...
[2] https://money.cnn.com/quote/shareholders/shareholders.html?s...