Artificial Radionuclide Background in French Metropolitan Territory

Between 1945 and 1980, more than 500 atmospheric tests of nuclear weapons were carried out by the USA, the Soviet Union, the UK, China and France. American and Soviet tests were by far the most numerous and the most powerful; they were carried out mainly between 1951 and 1958, then in 1961 and 1962, before the treaty putting an end to atmospheric testing, ratified in 1963 by the United States, the Soviet Union and the United Kingdom. Atmospheric tests released numerous radionuclides into the atmosphere, some twenty of which were regularly detected and measured in the air in France. . Most of the radionuclides with short half-lives (less than 3 years) released during these tests disappeared fairly quickly through radioactive decay. Today, only tritium ( ³ H), carbon 14 ( ¹⁴ C), cesium 137 ( ¹³⁷ Cs), strontium 90 ( ⁹⁰ Sr) are measured in the environment, plutonium isotopes ( ²³⁸ Pu, ²³⁹ Pu, ²⁴⁰ Pu and ²⁴¹ Pu), as well as americium 241 ( ²⁴¹ Am) from the decay of plutonium 241.

Air masses contaminated by the Chernobyl accident reached France in early May 1986, mainly between 1 ^er and May 5. . Of the ten or so radionuclides from this accident detected in the air and in plants, the three main ones were iodine-131 and caesium-134 and -137. Iodine-131 largely disappeared over the following three months through radioactive decay; caesium-134 could be measured in the environment until the early 2000s; only caesium-137 remains detectable today in most environmental components.

The mass and volume activities of radionuclides from nuclear weapons testing and the Chernobyl accident in atmospheric, terrestrial, continental aquatic and marine environments make up the bulk of the artificial radionuclide "background" in the French metropolitan environment....