Not that easy to make an actual nuclear device (fission reaction), so that is unlikely. Pretty easy to gather some radioactive isotopes into a can and pack it with an explosive, so that the burst will disperse the isotopes over an area.

I now wonder if the Ukrainian attempts to reclaim the large nuclear power plants were attempts to get their hands on any fuel waste isotopes in storage at the facilities. They would be ideal for the purpose.

They truly are Nazis if they detonate a dirty bomb on their own soil. Just like Hitler, it seems they are willing to burn everything down. After all, Hitler was willing to destroy Germany rather than surrender.