unchecked, lead to a full meltdown

The two reactors where the explosions occurred are both presumed to have already suffered partial meltdowns — a dangerous situation that, if unchecked, could lead to a full meltdown.


unchecked

(ŭn-chĕkt')
adj.

1. Not held in check; unrestrained: an unchecked flow of water; an unchecked temper.
2. Not checked for accuracy, efficiency, or flaws: an unchecked list.
3. Informal. Of or relating to a square in a crossword that is part of only one word instead of two.