Behaviour of ²³⁸U family radionuclides in continental environment: Case of the U mining area near Limoges (France)

¹ Laboratoire des Sciences du Climat et de l'Environnement, Domaine du CNRS, Av. de la Terrasse, 91198 Gif-sur-Yvette, France
² Present address: IRSN/DEI/SARG/LERAR, BP. 17, 92262 Fontenay-aux-Roses, France

Abstract

The objectives of this work are to study the behaviour of ²³⁸U and its daughters in the continental environment and to determine the radiological impact of U mining past activities in the Haute-Vienne French administrative division. The distribution of radionuclides among different size fractions was investigated upstream and downstream mines. Particulate (>0.45μm) and dissolved (<0.45μm) fractions were separated by filtration and analysed by gamma spectrometry. A preconcentration step by evaporation was elaborated and validated for liquid samples. Results indicate that radiological impacts of U mines are the enhancement of radionuclides activities and a change of their distribution between particulate and dissolved fractions at 0.45μm. While activity levels depend on the input intensity, the distribution is controlled by the mine water treatment witch reduces drastically the contribution of mine radionuclides in streams. Analysis of particles from traps and sediments confirms that the distribution of mine radionuclides promote their accumulation in lacustrian sediments. Nevertheless, the impact of the past activities is very limited in space. Indeed, it becomes weak at 10 km downstream the inputs and is no more detectable at 30 km downstream.