This particular article even has video of Russian military vehicles parked right inside one of the reactor buildings.
Would you really like a nuclear power plant to be unguarded??
It is now a Russian nuclear power plant in a war zone. If Ukraine wants to put Ukraine military outside to guard it, all they have to do is retake it with their counteroffensive.
Waiting for Godot the Grand Ukrainian Counteroffensive.
It'll be Million Man, man!
Look at the video. Those are supply trucks, which are currently being bombed all over Ukraine screwing up Russian logistics. Those are not "guarding" the nuclear power plant. They are being guarded BY the plant.