If you want to get spooky about it and do some really questionable research, I think you'll discover that post-2001 nuclear closures have been heavily influenced by their vulnerability to attack. Frank Barnaby published a book in 2004 called How To Build A Nuclear Bomb that, contrary to the title, is mostly about improvised and non-state-actor-level WMD attacks and strategies. His nightmare scenario was a 747 out of Heathrow hijacked upon takeoff and diverted to impact at Calder Hall. He observed that with vessel thicknesses designed in the '50s, Calder Hall was completely vulnerable to the impact of a large commercial airliner (and, despite being designed in the '50s, completely invulnerable to anything less than that). By 2004, of course, Calder Hall was already being decommissioned. I did further research because that's what you do when you're a writer. STNP, by contrast, was designed to withstand the impact of a large commercial jetliner. More than that, the NRC requires US reactors to pass an Aircraft Impact Assessment if they are to keep operating. Vessel breach on a nuclear reactor is a big deal - as it turns out, a much bigger deal than most amateurs can guess. Odds are good that anybody with the knowledge to carry out a targeted frontal assault on a nuclear reactor will recognize that the amount of ordnance and planning necessary can be more efficiently applied elsewhere. Beyond that, containment has been the fundamental design parameter for pretty much all modern reactors, of which I would consider Turkey Point an exemplar. Three Mile Island was a wicked bad meltdown. Radiation from Three Mile Island didn't broach 1mrem over background. Fukushima? Certainly not great... but radiation exposure there was largely a local problem. Now - shall we talk about real fallout? The data likely isn't there because the critical release you care about requires the kind of violence where you've likely got other problems. You can't just crack a reactor like an egg and if you've got the kind of juice to crack a reactor like an egg, you can do more impactful things like, well. You know. 9/11.
