The Hexafluride barrel recipe is missing somehow. Helmod shows it and I can make Hexafluride, but not barrel it. I have Anti's Science installed which changes some related tech - could be a conflict.

Managed to fix it. In data_raw_edits.lua:

--Change Nuclear Power research to unlock Hexafluoride production
if data.raw["technology"]["uranium-processing"] then
    -- Anti's Science: unlock via uranium-processing instead of nuclear-power
    table.insert(data.raw["technology"]["uranium-processing"].effects, {type = "unlock-recipe", recipe = "uranium-hexafluoride"});
else
    table.insert(data.raw["technology"]["nuclear-power"].effects, {type = "unlock-recipe", recipe = "uranium-hexafluoride"});
end

And add a migrations/SigmaOne_Nuclear_1.2.2.lua file:

for _, f in pairs(game.forces) do
    if f.technologies["uranium-processing"].researched then
        f.recipes["fill-uranium-hexafluoride-barrel"].enabled=true
    end
end

Finally, update version number in info.json and zip/directory name.

Sorry it took so long, but I'm uploading the updated version right now. I also credited you in the code. Thanks for reporting (and fixing!) this.