I think this is mainly a psychological move. It has people talking about nuclear fallout, radiation etc. That's the point.
If it turns out they don't try to take Kyiv, I stand corrected.
But practical necessity has certainly not stopped the Russians from also trying an infowar attack based on Chernobyl's totemic power, as you say.
Right now the wind is blowing North.
https://earth.nullschool.net/#current/bio/surface/level/anno...
It makes more sense as a bargaining chip with Ukraine than as a chip with the EU.
What's the proposition? Russia's already committed to ending the idea of Ukraine as a country.