[en] In this study, we focused on the study of samples from six naturally radioactive mineral springs of varying radioelement concentration gradient (<3.71 ppb U) in the Massif Central sampled in autumn, and of soil core samples from a wetland downstream of the old Rophin mine, characterised by a uranium rich layer (>1200 ppm U). The bacterial biodiversity of these samples was characterized by next generation sequencing (Illumina Miseq), targeting the ¹⁶S rRNA gene. In addition, the influence of the different physico-chemical parameters on these bacterial communities was studied. The results highlight the presence of bacterial populations specific to the environments most charged with uranium. To understand how these bacteria have adapted to these particular conditions, a culture on non-selective medium was performed for samples from these six mineral springs and a seventh with a higher concentration of uranium (15.91 ppb U); and from samples of the soil core of the wetland downstream of the former mine site. A collection of several hundred bacterial strains has been formed and identified, many of which are close to species known to be radioresistant. Some of these bacteria have been studied for their potential resistance and interaction with uranium. Indeed, the diversity of mechanisms used to resist high concentrations of uranium and other metals (biosorption, bioaccumulation, bioreduction, biomineralization) suggests that bacteria from these environments may have an impact on the migration and the toxicity of these elements into the environment

[en] The watershed has been equipped since 2019 with piezometers and surface sensors to monitor the water (electrical conductivity, temperature and water level). Meteorological data is available to identify patterns for precipitation and temperature regimes for the wet and dry seasons. First results from measurement campaigns of the water table in 2021 and 2022 confirm the presence of a groundwater table in the wetland, which is rather close to the surface and varies depending on meteorological conditions. A geophysical survey was carried out in October 2022 to provide the geometry of the different horizons of the wetland, as well as information on water content, permeability and CEC. In parallel, parameters such as soil permeability, soil porosity, diffusion coefficients and dispersivity will be obtained by laboratory measurements in Spring 2023. Surface mapping data (dose rates and gamma-ray spectroscopy analysis) and Light Detection and Ranging (Lidar) data are available as well as information about water chemical composition and soil/sediment mineralogy both in the wetland and in the Gourgeat stream. To evaluate radionuclides sorption onto the various soil layers and partition of radionuclides between solid and liquid phases, distribution coefficients are determined either experimentally (K_d) or modelled with the mechanistic 'Smart K_d' approach. A description of water flows and soil layers to be modelled is presented. In a first approach assuming a saturated zone, modelling of the three layers system will be performed in 1D and 2D. Two types of simulation will be considered, one with a low flux regime when the stream and the wetland seem to be disconnected and the other with a high flux regime when the stream and the wetland should be hydraulically connected. The aim is to evaluate the evolution of uranium and radium concentration within the layers of the wetland and also to quantify the concentrations of those radionuclides released into the environment, i.e., groundwater and Gourgeat stream

[en] The TIRAMISU collaboration gathers expertise from biologists, physicists, radiochemists and geologists within the Zone-Atelier Territoires Uranifères (ZATU) in France to analyze the radiation exposure of microorganisms living in naturally radioactive mineral springs. These springs are small waterbodies that are extremely stable over geological time scales and display different physicochemical and radiological parameters compared to their surroundings. Water and sediment samples collected in 27 mineral springs of the volcanic Auvergne region (Massif Central, France) have been studied for their microbial biodiversity and their radionuclide content. Among the microorganisms present, microalgae (diatoms), widely used as environmental indicators of water quality, have shown to display an exceptional abundance of teratogenic forms in the most radioactive springs studied (radon activity up to 3700 Bq/L). The current work presents a first assessment of the dose received by the diatoms inhabiting these ecosystems. According to ERICA tool, microorganisms living in most of the sampled mineral springs were exposed to dose rates above 10 μGy/h due to the large concentration of radium in the sediments (up to 50 Bq/g). Radiological analyses of water and sediments were used as inputs to Monte Carlo simulations at micro-(GATE) and nano- (Geant4-DNA) scale in order to assess the direct and indirect damages on the diatom DNA.

[en] The contributions of this collective book, proposed by experts and researchers in sociology, philosophy, physics and chemistry, first address the issue of ancient uranium mines. The authors discuss the historical and patrimonial aspects related to these sites, the inventory activities, and of course the associated risk management. The second part deals with the choice of future electronuclear reactors while considering time scale issues for their reactions, their control, their wastes, and also by discussing the various envisaged social and technical processes involved in the decisions on reactors of fourth generation. The third part addresses the issue of long life wastes, and more precisely the ability of science to model the long term (radioactivity and the long term, time models and their limitations, sciences involved in the issue of radioactive waste storage), the issue of an eternal deposit of long life wastes, and the genesis of the notion of waste

[en] Whereas it is impossible to describe the Big-Bang, stellar structures or matter birth without understanding what is going on at the infinitely small level (quarks, leptons, bosons, and so on), the author reports what is already known and what is being searched for in the infinitely small and infinitely large in order to develop theoretical models to explain black matter, black energy or quantum gravitation. He also presents large international installations which have been designed to perform these studies at the speed of light, and at the limits of matter properties