An assessment of plutonium and americium distribution in the lower Rhone Valley environment (France)

¹ HEMISPHERES, 2 bis rue Fargès, 13008 Marseille, France
² IPSN/DPRE/SERNAT/LERCM, CE Cadarache, bâtiment 153, 13108 Saint-Paul-lez-Durance cedex, France

Abstract

As the result of global fallout occurring from 1945 to 1983, actinides are uniformly present at trace levels in the environment. However, in the lower Rhone valley, higher Pu and Am activities are measured, due to a direct or indirect input of radionuclides originated from Marcoule nuclear reprocessing plant releases. Associating measurement and modelling results, a balance of stocks and fluxes of these alpha-emitting actinides in the environment is proposed for the 1950-1998 period. The ²³⁸Pu/^239+240Pu activity ratio is used as a tool to trace and quantify the Marcoule installation's contribution to the total contamination of different environmental compartments. On a global surface of 11000 km², the soil is the main terrestrial reservoir where 770 GBq of Pu and Am alpha emitters are stocked. More than 95% of this soil contamination is due to the global fallout. Since 1950, the lower Rhone River carried more than 1000 GBq of ²³⁸Pu, ^239+240Pu and ²⁴¹Am to the Mediterranean Sea, of which 90% originated from Marcoule liquid release. Therefore, the Rhone River water is considered as another source term for the contamination of the terrestrial environment, because of irrigation practices and accidental floods.