I wonder if there is already a NATO response formulated in case of a radiological incident deliberately perpetrated by the Russian forces? Or for that matter, if they use chemical weapons or other WMD in urban areas (including the so-called thermobaric bombs). There certainly should be, and it should be communicated to the Russian side via the usual back channels. For once we should be pro-active, rather than acting to every atrocity as if it came as some kind of surprise. Putin wants us always on the back foot and we should not play his game.
Free nation armies do not "do" chemical warfare on the whole, our WMD option is nuclear or nothing. Unfortunately Russia has done so including in the UK, and are apparently trying to normalise this starting at a very small or deniable scale. Putin knows that if Russian forces used such WMD on scale it may well lead to NATO thermonuclear response, as there are such red lines that we in the west do not allow to be crossed. This might be the real reason for his bluster about atomic weapons previously discussed. It might well be the realisation that West that is forced to use nuclear weapons first to retaliate against a chemical attack, surely more plausible than Russia using nuclear weapons first in response to declaration of a "no fly zone".
Or perhaps that was again typical russian deflection. I heard somebody once saying that with russia it is important not to respond to what they are saying but look for what they are trying to distract you from. A chemical war or deliberate radiological incident could be that thing. And we must not allow bluster on nuclear missiles to be used as a means to make chemical or radiological attacks seem somehow acceptable by comparison. We need to keep our "red lines".
I feel that the incident at the atomic power plant is very bad and should be the pretext for NATO involvement in this war. Demilitarised zones of, say, 100km radius around these major facilities should be established, and the cities while we are at it. And NATO ground as well as air troops should be deployed to enforce them.