noun
amount of radioactivity
Technical term used in physics, nuclear engineering, and radiation safety contexts.
この地域の放射能量は安全基準を下回っている。
The amount of radioactivity in this area is below the safety standard.
放射能 refers to radioactivity itself (the property or phenomenon), while 放射能量 specifically refers to the measured amount or quantity of radioactivity.
Compound of 放射 (ほうしゃ, 'radiation') + 能 (のう, 'ability') + 量 (りょう, 'amount'). The exact historical derivation is uncertain; the term is a modern technical coinage.