Design-basis event

Beyond-design-basis events can reduce or eliminate the margin of safety of the structures, systems and components, possibly resulting in a catastrophic failure. The Fukushima nuclear accident was caused by a "beyond-design-basis event": the tsunami and associated earthquakes were more powerful than the plant was designed to accommodate. The plant withstood the earthquake but the tsunami overflowed the seawall. Since then, the possibility of unforeseen beyond design basis events has been a major concern for plant operators. == See also ==