All 5 Uses

radioactivity
in
The Hunt for Red October
(Auto-generated)

Farther aft, saturated steam in the "outside" or nonradioactive loop of the heat exchange system emerged through clusters of control valves to strike the blades of the high-pressure turbine.†
Chpt 7.

nonradioactive = lacking emission of a stream of particles in nuclear decay

standard prefix: The prefix "non-" in nonradioactive means not and reverses the meaning of radioactive. This is the same pattern you see in words like nonfat, nonfiction, and nonprofit.
The only radioactivity was in the inside loop.†
Chpt 7. *

radioactivity = the emission of a stream of atomic particles in nuclear decay
The reactor coolant, which carried short-lived but dangerous radioactivity, never flashed to steam.†
Chpt 7.
The water was dangerously radioactive as a result of the fission reaction taking place within the uranium fuel rods.†
Chpt 8.

radioactive = producing a stream of atomic particles through nuclear decay
In a minute there was a meter-wide puddle of radioactive slag, enough to form its own critical mass.†
Chpt 8.

Definitions:

(1) (radioactivity)
the emission of a stream of atomic particles in nuclear decay
(2) (meaning too rare to warrant focus)