I agree with all your proposals
Looking at each and every tag, they all come from 2016 or earlier. They've been alive for 7 years. But even with 7 years of use, each of the tags got less than 50 questions each (and two less than 10!). It's a very strong sign they aren't attracting people's eyes and ears.
Because of that -and because there are either synonymous or more generic tags-, they can and should be merged together. They're not useful enough to help people find and categorize questions in a reasonable manner, all while cluttering the tag list.
So to keep it straight and short, I wholefully agree to merge weak-force, strong-force, and radioactivity into the tags you suggest (nuclear and radiation respectively).