I did some design for a "nuke related" project years ago for [a government agency involved with all things nuclear]. It was for a vehicle storage building/maintenance shop on a "nuke site" (not a power plant, not a missile factory as far as I know) in the US. IIRC it was about 10k sq. ft. with a ~2k sq. ft. mezzanine and an overhead crane. In reality it should have been a PEMB but after 5 months of hemming and hawing the owner decided to go with steel framed.
So, whatever you think a ~10k sq. ft. 25'-30' tall simple steel framed building should cost, add a massive multiplier.
Despite owner's self proclaimed "best effort to follow typical commercial and industrial building design and construction practices"...the project ended up being being bid right around $10MM. TEN MILLION. I'm not sure what the final price tag was after construction but I'm sure you could tack on another mil.
In my opinion most of the "inflation" came from the multiple layers of bureaucrats/project managers/eggheads, none of whom had any real experience whatsoever in "typical commercial and industrial building design and construction", ALL providing input on every single aspect of this project. From the high level "what kind of building do we want" all the way to "according to *some random book* it is best practice to not weld the tips of wide flange column flanges to a baseplate - revise detail" and "I read in a publication that fiber reinforcing for the slab on grade provides enhanced crack control, so we would like that in addition to the rebar... oh, and we would also like several different specs of densifier on the slab" and "We noticed that it is common to use RED concrete for duct banks so people know they are about to dig through a power line" (red pigmented concrete is about a 1000% markup, and this site was thousands of feet from the nearest power service).
I swear I think they were just googling "vehicle maintenance building" and cherrypicking all of the coolest/newest/fanciest components that they could possibly imagine. Seemed like the pet project of management at the site. I digress...
Every submittal had at least a dozen different review stamps on the cover sheet(s), with a bloodbath of comments. There were mechanical (like, gizmo engineers, not HVAC engineers) reviewing and commenting/rejecting steel shop drawings and mix designs, and providing input on roofing membrane selection.
I'm sure other factors were incidentals like security escorts/oversight, background checks, Buy American, owner performing in person inspections of the steel fab shop, etc etc etc.
So, that's my experience with "nuke sites". Your mileage may vary.