Western officials are engaged in “prudent planning” behind the scenes to prevent chaos and panic in their home countries in the event Russia was to detonate a nuclear bomb in or near Ukraine. Although a nuclear crisis is considered highly unlikely, the insider said officials internationally were re-examining plans to provide emergency support and reassurance to populations fearful of nuclear escalation. Hints of the thinking emerged in a briefing by an official on Friday, who was asked if there would be measures in place to prevent panic buying or people fleeing cities en masse in fear of escalation after a...