Well a group of people need to go but yes

Dirty bombs are a meme weapon that would barely cause damage except psychologically. If it spreads everywhere it’s too diluted to do much and if it remains concentrated then the scope is too small to affect many people. Their sole advantage is that people are terrified of them because they are ignorant about how bad they are as weapons. So no a dirty bomb is not spreading across Europe and killing hundreds of thousands of people, a hypothetical dirty bomb is literally nothing compared to the thousands of nuclear tests, Chernobyl release, Kyshtym disaster etc. that did not have death tolls anywhere remotely near a million. Even the actual atomic bomb strikes on populated cities of Japan combined did not kill a million.

This is not to say it would be good for Ukraine to use dirty bombs, absolutely not. Negligible damage to Russia except for causing a massive scare to their people that would be condemned globally makes that a terribly counterproductive option to undertake vs. keeping on bombing refineries and so on.

What's next? Nuking civilian populations?

no, only the US does that