Thanks! The reactor idea was born from the theme for the Brackeys Game Jam (nothing can go wrong) which led to the idea of building a bomb because bomb = inevitably something goes wrong. I then added combat when I felt confident to do so, and it evolved into a TD. My first devlog dives into greater detail on the ideation process. In terms of games, people have called it Frostpunk + Tower Defense.
I will check out Forts!