An atomic detonation differs from the chemical and thermal explosions that can accompany a damaged reactor. Engineering safeguards make a catastrophic event unlikely in normal operation, but a warship is deliberately exposed to weapons that can rupture systems and create high-velocity holes. Older reactor designs may also lack modern self-stabilizing behavior if multiple protections are lost. A reactor does not have to explode like a bomb for battle damage to a nuclear-powered ship to become disastrous.
Notable Point · 1:42:17-1:45:07
Why battle damage changes nuclear-reactor risk
A naval reactor is not an atomic bomb, but missiles, mines, broken safeguards, and older core designs can still produce a destructive thermal or chemical event.