Because you must be continually exposed to the radiation for six or seven years, and that can't be done in the Keeps.

Every day, people are continually exposed to a wide variety of potentially arousing stimuli.

Rock falls occur on the cliff face very frequently, continually exposing new fossils.

They continually exposed me to nanites of their own.

The citation says that Hampshire "continually exposed himself to hostile fire" while saving the lives of his fellow soldiers.

Rain is supposed to wash away the powdery residue, continually exposing a clean surface.

Children are continually exposed to sports through extensive media coverage, school programs, after-school programs and summer camps.

This provided an element of stability to counterbalance the mental extremity to which they were continually exposed.

His parents kept a house full of instruments, and a singer-songwriter cousin continually exposed him to new sounds and ideas.

The granules are continually exposed by traffic wear, and release calcium chloride onto the surface.