even a stray bullet won't suddenly restart the fission process, if they even fired one. was there any large ukrainian military presence or heavy firefights at all? only the levels have gone up from kicking up the dust (as to be expected) which twitter and reddit took for chernobyl 2.0.
I also doubt the russians are dumb enough to mess with or let anyone else mess with it, so the worst thing that could happen is someone not cataloging the daily radiation levels or something.
EDIT: just thinking about it, they're still slavs, so... eh I guess anythings possible.