That would be very foolish on Russia's part. If radioactive material was released, it would definitely impact Russia, especially the western regions that are geographically close to Ukraine and Belarus. Radiation doesn’t respect borders, something Russia should be very aware of.
Due to the extreme risk of hurting themselves, you'd have to ask why do it in the first place? Damaging the dome would do nothing to end the war. In fact, it would probably escalate the further with more support being thrown at Ukraine.
I'm not saying it wasn't Russia. I'm just struggling to understand the logic of such a dumb move.