Presumably even the Russians would want to avoid nuking their own troops (or am I being too naive about that?) In a complex battlefield situation that might not be easy. To minimise 'friendly' fire losses, one might expect measures to be taken to withdraw Russian forces from the danger areas, or to ensure that they take protective measures (donning radiation suits and breathing kit, etc). Coded warning messages would need to be sent in advance. Western (or Ukrainian) intelligence might well detect such warning signs. Or to be pessimistic, maybe measures such as the reported withdrawal of Russian troops from the west of the Dnipro river, and the evacuation of civilians from Kherson, are themselves part of such precautionary tactics.