Depends on the type of accident. If Zaporizhzhya NPP was to have a meltdown or an explosion. It’d poison the ground, parts of the air and probably some water.

If a dirty bomb was set off in say Kherson. The damage would mostly stay in the city. Buildings would possibly get blown up depending on where it was set off. There’d be radiation but not very high levels. Only people close to the detonation site would feel effects of radiation sickness. The main damage would come from the explosion.

While a plant accident would likely spread radiation illnesses for kilometres in multiple directions

A plant meltdown with a containment breach is essentially the same thing as a continuously exploding dirty bomb. Imagine a firecraccker blowing smoke out once vs a much larger fire just continuously burning and smoking.