The value used to determine the Design Basis Flood is a 10000 year recurrence. Over a 100 year lifespan, there is around a 1% chance of that flood happening. Th

The value used to determine the Design Basis Flood is a 10000 year recurrence. Over a 100 year lifespan, there is around a 1% chance of that flood happening. The consequences of loss of all power including backups is the loss of the plant + huge evacuation costs and possible loss of life. $1M is very cheap to protect a multi-billion plant in this context.