238Pu, 239+240Pu and 241Am levels in the terrestrial and aquatic environment of the Loire and Garonne rivers basins (France)

Plutonium and americium long-lived alpha emitter isotopes can be found in the environment because of atmospheric global fallout due to thermonuclear tests performed between 1945 and 1980, to the American SNAP 9A satellite explosion in 1964, to the Chernobyl nuclear power plant accident,... In France, the nuclear safety authority does not allow the release of artificial alpha emitters from nuclear power plants. Thus, monitoring is performed to verify the absence of these alpha emitters in liquid discharges to respect the limits set by the regulations. These thresholds ensure a very low dosimetric impact to the population compared to other radionuclides. With the objective of environmental monitoring around nuclear facilities, activity measurements of long-lived alpha emitters are carried out to detect the traces of these radionuclides. Analysis of low activity by alpha spectrometry after chemical steps were performed and used to determine the 238Pu, 239+240Pu and 241Am activities on a large set of environmental solid samples likely to be encountered in environmental monitoring as soils, sediments, terrestrial and aquatic bio-indicators. The samples collected in the terrestrial and aquatic environment of the Loire and Garonne rivers basins (France) was investigated for the 2009-2014 period. It was found that the mean activity concentration of the most frequently detected was for the radionuclide 238Pu: from <0.00031 to 0.0061 Bq/kg dry in terrestrial samples and from <0.00086 to 0.011 Bq/kg dry in aquatic samples; for the radionuclide 239+240Pu: from 0.00041 to 0.150 Bq/kg dry in terrestrial samples and from 0.0023 to 0.240 Bq/kg dry in aquatic samples and for the radionuclide 241Am: from <0.00086 to 0.087 Bq/kg dry in terrestrial samples and from 0.0022 to 0.120 Bq/kg dry in aquatic samples. 238Pu/239+240Pu and 241Am/239+240Pu ratios determined are in accordance with an environmental contamination due to thermonuclear tests. Document available in abstract form only. (authors)