What 'rational' nation would bring thermonuclear destruction upon itself? The 'signature' of Iranian manufactured Enriched Uranium is known. Any detonation of same would leave a 'flaming datum' which would be pursued by Israel and probably one or more other nations. The 'cold rationality' of the Soviet Union did not result in a nuclear attack on the USA during the Cold War despite the ravings of the extreme right. Indeed the Soviets never even put their forces on high alert during the Cuban Missile Crisis; nor did they launch on warning during the 1983 War Scare. Nor has the irrational government of North Korea nuked Seoul for laughs because to do so would result in US retaliation. Any nation which uses nukes is condemning itself. Other nuclear powers would have to act in self-defense.
UN says bombing of Aleppo among 'the worst' of Syrian war (AP)
from the article: Rational and dangerous