None or insignificant structural damage (damage ratio: 0 - 0.05%).

Minor buckling of some cross braces in support structure (damage ratio: 0.05 - 1.25%).

Failure of some connected piping; repairable damage to the reactor support system; moderate likelihood of realease of reactor contents (1.25 - 20%).

Failure of most piping connections; reactor support system almost completely failed; almost certain release of reactor contents (20 - 65%).

Failure of all piping connections; reactor support system completely failed; reactor itself severely damaged (possible buckling and shearing); contents of reactor released (65 - 100%).