Heterogeneous modeling of the uranium in situ recovery: Kinetic versus solubility control

The uranium in situ recovery (ISR) is a mining technique, which involves injecting an acid or alkaline solution, into the deposit to selectively dissolve uranium. The solution enriched in uranium is pumped out and processed. Once the uranium is removed, reagent is added to the solution, which is then reinjected. This method is particularly suited to deep and low-grade deposits located in confined aquifers. In this work, we focus on the case of the Tortkuduk deposit, in Kazakhstan, where the reagent is sulfuric acid. The main objective of this work is to understand how the uranium production can be increased while the sulfuric acid consumption is maintained as low as possible. It requires devising and validating an ISR phenomenological model, using all available tools: experiments, production data and numerical simulation, from 1D homogeneous to 3D heterogeneous models

Kinetic reactive transport modelling of column tests for uranium In Situ Recovery (ISR) mining

International audienceNumerical modelling of the interaction between solution and rock is examined in order to improve the management of U In Situ Recovery (ISR) mining. Two ‘classical’ types of leaching experiments were performed: (1) tests in batch reactors; and (2) extraction in flow-through columns. A comprehensive interpretation of the complete leaching test results (mineralogy of the samples and chemical analysis of leachates) led to the development of a conceptual model with reasonable assumptions about dissolution and precipitation reactions during the acid leach of the columns. This conceptual model was tested and validated by numerical modelling of the two types of laboratory experiments. Batch experiments were simulated with the geochemical code CHESS in order to model the leachate solutions and to calibrate the geochemical reaction paths and their kinetic laws. The geochemical models with kinetics successfully simulated the trend of leachate’ chemistry in the two types of experimental tests (batch and column). They resulted in a proposal of a 1D hydrogeochemical transport model of the ISR process at laboratory-scale. Furthermore, a sensitivity analysis conducted on the 1D-calibrated model made it possible (1) to determine factors controlling leaching reactions; and (2) to quantify their respective influence on the uranium recovery in terms of acid consumption and leachate volume to treat in the plant

Amino Acid Availability Controls TRB3 Transcription in Liver through the GCN2/eIF2α/ATF4 Pathway

In mammals, plasma amino acid concentrations are markedly affected by dietary or pathological conditions. It has been well established that amino acids are involved in the control of gene expression. Up to now, all the information concerning the molecular mechanisms involved in the regulation of gene transcription by amino acid availability has been obtained in cultured cell lines. The present study aims to investigate the mechanisms involved in transcriptional activation of the TRB3 gene following amino acid limitation in mice liver. The results show that TRB3 is up-regulated in the liver of mice fed a leucine-deficient diet and that this induction is quickly reversible. Using transient transfection and chromatin immunoprecipitation approaches in hepatoma cells, we report the characterization of a functional Amino Acid Response Element (AARE) in the TRB3 promoter and the binding of ATF4, ATF2 and C/EBPβ to this AARE sequence. We also provide evidence that only the binding of ATF4 to the AARE plays a crucial role in the amino acid-regulated transcription of TRB3. In mouse liver, we demonstrate that the GCN2/eIF2α/ATF4 pathway is essential for the induction of the TRB3 gene transcription in response to a leucine-deficient diet. Therefore, this work establishes for the first time that the molecular mechanisms involved in the regulation of gene transcription by amino acid availability are functional in mouse liver

Rapid response to the M_w 4.9 earthquake of November 11, 2019 in Le Teil, Lower Rhône Valley, France

On November 11, 2019, a Mw 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE-SW La Rouviere normal fault in reverse faulting in agreement with the present-day E-W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics

Reactive transport upscaling at the Darcy scale: A new flow rate based approach raises the unsolved issue of porosity upscaling

International audienceThis article demaonstrates that permeability upscaling, which can require complex techniques, is not necessary to significantly decrease the CPU time in reactive transport modeling. CPU time depends more on the geochemistry than the flow calculation. Flow rate upscaling is proposed as an alternate method to permeability upscaling, which is more suited to time-consuming flow resolution. To apply this method, a finite volume approach is most convenient

In the shade of the truncated gaussian simulation

International audienc

Reactive transport simulation of Uranium ISL at the block scale: a tool for testing designs and operation scenarios

International audienceThis study details the development of a tool simulating in the 3D fluid flow as well as the coupled physical and chemical processes in an ISL production block. The model relies on an appropriate description of uranium bearing aquifer: 3D geologic model, geostatistical simulation of hydrodynamic parameters, the uranium and other mineral concentrations. Also, a correct assessment of the chemical reactions at stake is necessary. It is then possible to simulate the ISL operations with a reactive transport approach (code HYTEC). Among other simulation results available, the evolution of the uranium concentration at production wells can be predicted. The model was applied at a technological block scale (75 technical wells). The simulations allow to reproduce the behaviour in terms of uranium recovery and to test scenarios of production for optimization purposes

Reactive transport simulation of Uranium ISL at the block scale: a tool for testing designs and operation scenarios

International audienceThis study details the development of a tool simulating in the 3D fluid flow as well as the coupled physical and chemical processes in an ISL production block. The model relies on an appropriate description of uranium bearing aquifer: 3D geologic model, geostatistical simulation of hydrodynamic parameters, the uranium and other mineral concentrations. Also, a correct assessment of the chemical reactions at stake is necessary. It is then possible to simulate the ISL operations with a reactive transport approach (code HYTEC). Among other simulation results available, the evolution of the uranium concentration at production wells can be predicted. The model was applied at a technological block scale (75 technical wells). The simulations allow to reproduce the behaviour in terms of uranium recovery and to test scenarios of production for optimization purposes