Thesis: The Rhône and the Loire are the most nuclearized french rivers with several nuclear power plants (NPPs). From the middle of the 20th century, the uranium mines located in the Loire watershed extracted the uranium ore used for the manufacture of nuclear fuel. Along the Rhône, nuclearization began with the construction of the first reactors intended for the production of plutonium for military use. Medicine, scientific research, agriculture and even watchmaking have also led to the spread of artificial radionuclides or changes of concentrations of naturel origin radionuclides. These rivers collect also artificial radionuclides drained from soils marked by atmospheric fallout from military nuclear tests (between 1945 and 1980), then from the Chernobyl accident (1986). Since the early 1980s, these rivers have been regularly monitored for radioactivity levels. However, knowledge gaps remain regarding several radionuclides for which analysis techniques were not developed or concerning their origins (watershed or industries). Investigating long-term time series is fundamental in order to identify the origin of radionuclides, better understand their trajectory at the watershed scale and assess the time needed for these environments to clean up these contaminants (resilience). The study of multiple radionuclides and physico-chemical parameters measured in sedimentary archives collected in sediment accumulation zones of the Rhône and the Loire allowed to retrace the nuclear history of these rivers