The background noise designs the activity of the different radionuclides present in the environment, outside any current human activity (nuclear industry, other industies, discharges from hospitals, ...). This background noise results partially from natural sources, and partially from the persistence of old contributions of artificial radionuclides, which concerned the entire territory;  these include fallout from atmospheric nuclear weapons and fallout of Chernobyl accident. This background noise contributes to the radiological exposures to which the population is subject. This chapter describes natural and artificial background noises.

NATURAL RADIOLOGICAL BACKGROUND NOISE

Natural radiological background noise has two origins: telluric radionuclides, present on Earth since its formation, and cosmic radiation, which permanently produces cosmogenic radionuclides.

Cosmic radiation and cosmogenic radionuclides in the environment

Cosmic radiation comes from the Sun and space (other suns and galaxies). It is composed mainly by protons. These protons interact with the atoms of the upper atmosphere which generates, on one hand, a secondary cosmic radiation, composed by electrons, protons, photons, neutrons, ..., and, on the other hand, the production of cosmogenic radionuclides, such as tritium (3H), carbon-14 (14C), beryllium-7 (7Be), and sodium-22 (22Na) in particular.

To know more about this subject, see the chapter 2 of the report on the radiological state of French environment, from january 2018 to december 2020:  « FRENCH RADIOLOGICAL BACKGROUND NOISE ».

ARTIFICIAL RADIOLOGICAL BACKGROUND NOISE

Knowledgeof the environmental background noise of artificial radionuclides, inherited from the fallout of athmosperic nuclear weapons testsand the Chernobyl accident meets several objetives: estimate the resulting exposures of populations, determine the the activity added due to releases from nuclear installations, and have an updated reference in the event of an accident, or any other cause of increase in an environmental radiological event. 

To know more about this, see the presentation video of the Articifial radiological background noise (IRSN video) ou The background noise of artificial radionuclides in the metropolitan French environment (IRSN report).