[tehjoker]

Assuming all that is true, reality is extremely unpredictable. Imagine a country is at war and they accidentally drop bombs on the reactor that crack the fuel and change the chemistry enough. A volcano erupts under the plant. Imagine a nuclear weapon going off nearby and causing a meltdown (for example, if the attacker was using a "low yield" neutron bomb). Imagine an astronomical phenomenon that happens to pass through the plant.

Low probabilities, but man they would suck.