The Only Use of

radiation
in
Atlas Shrugged

It was one of Colorado's new towns, the towns that had grown like a radiation from the Wyatt oil fields.†
Chpt 1.8

Definitions:

(1) (radiation as in: nuclear radiation)
particles emitted by unstable atomic nuclei

Generally, radiation is discussed in terms of harmful levels of radiation that cause sickness. However, there is a normal level of radiation that is not harmful and sometimes radiation is carefully used for beneficial purposes such as medical treatments that use it to kill cancer cells.
(2) (radiation as in: electromagnetic radiation)
energy sent out as invisible rays such as from heat, light, or radio waves