What are natural sources of gamma rays?
“Natural” sources of gamma rays occur in the environment without human intervention. Natural gamma rays are emitted by isotopes that are the natural products (daughter products) of the uranium decay series, the thorium decay series, and potassium-40. Uranium and thorium each decay into a series of unstable (radioactive) daughter products. The uranium decay series consists of about a dozen unstable elements in nature; this series of unstable isotopes finally decays to a stable (not radioactive) lead isotope. The decay of thorium forms a similar series of unstable elements. Potassium-40 decays into two stable isotopes, argon and calcium. The decay of each unstable isotope is marked by emissions of alpha particles, beta particles, or gamma rays. The decay of each specific isotope causes the emission of gamma rays that have characteristic energy levels that can then be identified in the energy spectrum measured by the spectral gamma tool.
