It's not equivalent to nuclear war with Ukraine in either the sense of relative risk (for the reasons I gave) nor in the sense in which the term "nuclear weapons" is actually used. Russia intelligence agents poisoned Alexander Litvinenko with radioactive polonium, but this was not called a nuclear attack because that's not what the term means.
One could argue, at most, that this would be equivalent to a radiological weapon ("dirty bomb"). But even then it wouldn't be correct because of the important difference between purposeful radiological dispersal and radiological dispersal as a side-effect of a legitimate military action.
Ah, behold, my fist is an atomic weapon because ultimately the damage it inflicts is because of the Coulomb repulsion force of the fist atoms with other atoms.
One could argue, at most, that this would be equivalent to a radiological weapon ("dirty bomb"). But even then it wouldn't be correct because of the important difference between purposeful radiological dispersal and radiological dispersal as a side-effect of a legitimate military action.