Creep and shrinkage of Intermediate Level Long Life containers concrete comparison between gamma-irradiated and non-irradiated material

International audienceMany of the facilities and structures involved in the radioactive waste repository call for reinforced concrete (RC) in their construction. RC is used for containers as well as for surface and deep geological structures. In this paper we will focus on concrete containers (about 2 cubic meter) which would receive 1 to 4 waste containers (steel or concrete waste packages) of Intermediate Level Waste Long Lived (ILW-LL). With regards to the present disposal concept these containers would be placed one above the others up to 4 levels in the repository cells. In such context, Andra has to demonstrate the continuous mechanical integrity of the structure all over the operating / reversibility period.Classical mechanical properties of this concrete, as compressive strength, tensile limit and Young modulus are well known in classical non irradiated environment and must be confirmed in irradiated environment. This present study deals with the assessment of creep, shrinkage and others physical properties both under and out gamma irradiation, the samples being at the same thermal and hydric conditions.Specific experiment has been developed to address these parameters using cylindrical concrete dedicated to creep measurement and prisms dedicated to shrinkage.Samples are split in two groups, half irradiated and half non-irradiated. Gamma-irradiation has been carried out at the dose level representative of such ILW-LL wastes ($\approx$30 Gy/h) during 8 months to reach a total dose near to 180 kGy in average.The results show only a very small dimensional differences between irradiated and non-irradiated concrete samples in the same order of magnitude both for creep and shrinkage samples. Irradiation at such dose does not induced significate mechanical deterioration of the cementitious material

Large-scale DNA-based survey of frogs in Amazonia suggests a vast underestimation of species richness and endemism

Aim: Mapping Amazonian biodiversity accurately is a major challenge for integrated conservation strategies and to study its origins. However, species boundaries and their respective distribution are notoriously inaccurate in this region. Here, we generated a georeferenced database of short mtDNA sequences from Amazonian frogs, revised the species richness and the delimitation of bioregions of the Eastern Guiana Shield and estimated endemism within these bioregions. Location: Amazonia, with a focus on the Eastern Guiana Shield. Taxon studied: Amphibia: Anura. Methods: We used an extensive DNA-based sampling of anuran amphibians of Amazonia using next-generation sequencing to delimit Operational Taxonomic Units (OTU) and their distribution. We analysed this database to infer bioregions using Latent Dirichlet Allocation modelling. We then compared endemism within these bioregions based on our results and the current IUCN database, and inferred environmental variables that contributed the most to the biogeographic pattern. Results: The recognized anuran species richness within the focal area increased from 440 species currently listed by the IUCN Red List to as much as 876 OTUs with our dataset. We recovered eight bioregions, among which three lie within the Eastern Guiana Shield. We estimated that up to 82% of the OTUs found in this area are endemic, a figure three times higher than the previous estimate (28%). Environmental features related to seasonal precipitations are identified as playing an important role in shaping Amazonian amphibian bioregions. Main conclusions: Our results have major implications for defining future conservation priorities of this vast area given that endemism in most Amazonian bioregions is vastly underestimated, and might therefore hide a large portion of threatened species. Moreover, these findings raise concern about meta-analyses based on public databases within Amazonia dealing with poorly known groups