They really need to stop being woolly around the edges on this, the West keeps bleating on about a robust response, grave consequences etc, one does hope that behind closed doors they are telling the Russians privately one nuclear explosion in Ukraine will result in an equal response in Moscow or similar, just to show that the consequences will be that severe and leave them under no pretensions that the result will be anything else. So that they know in no uncertain terms that letting that genie out of the bottle will have far reaching consequences.
I.E calling their bluff, which by continuing the grain exports after Russia tried to stop them has proved that standing up to them they have nowhere to turn..