Etude de la reactivite du dioxyde d'uranium monocristallin vis-a-vis des processus de dissolution en milieu acide cinetique et reactivite aux interfaces.

International audienc

Capability of the Kd model to predict radionuclides behaviour and transport in unsaturated columns under steady flow conditions

In the frame of the IRSN Chernobyl Pilot Site Project, a waste trench containing hot particles was instrumented to study the fate of radioactive pollutants. Results have shown the formation of a 90Sr plume in the downstream aquifer, mainly present in the Aeolian layer after 15 years. Laboratories experiments were performed to analyse the transport of 90Sr and 137Cs in the Aeolian sand in both saturated and unsaturated conditions. Batch experiments were performed to study the chemical equilibrium state of the soil/solution system under static conditions. Stirred flow-through reactor experiments were performed to study the kinetics and reversibility of sorption reactions at the surface of solid particles under dynamic conditions. Column experiments in the structured porous media were also performed in saturated and unsaturated flow conditions. Experimental data pointed out a non-linear, instantaneous and reversible sorption process of 90Sr. 137Cs exhibits a non-linear behaviour with a partial irreversible sorption process. A suitable cation-exchange model was used to describe the solute/soil reactions. The former model was coupled with transport models to describe behaviour of 90Sr and 137Cs in both saturated and unsaturated steady flow conditions. Main transport parameters were identified and discussed. An effective simple Kd type approach to describe radionuclides transport properties under unsaturated conditions was evaluate

Evaluation of distribution coefficients for the prediction of strontium and cesium migration in a natural sand at different water contents

Contaminant distribution coefficient determined under saturated conditions are often used to model solute transport in the vadose zone. However, the water content of porous media may affect the transport behaviour of conservative and sorbing solutes. We performed column experiments using sand from Chernobyl area and we investigated the transport of tritiated water as conservative tracer, $^{85}$Sr and $^{134}$Cs as reactive solutes at different water saturation levels. The results indicate that when the Kd model is applicable, a decrease of the water content leads to a decrease of the Kd value

Impact of complex irradiation scenarios on the structure and the properties of the International Simple Glass

International audienceThis study addresses the consequences of three irradiation scenarios on the structure and macroscopic properties of the ISG glass. The coupling effect between 2.5 MeV electron irradiation (simulating the effects of beta particles and gamma rays) and 7 MeV Au irradiation (simulating the nuclear collisions of the recoil nuclei of alpha decays) was studied by comparing two monobeam irradiations with a sequential double beam irradiation. Various experimental techniques were used to characterize the glass structure and properties, combining Raman, NMR, IR-ATR spectroscopies, hydrostatic weighing, He pycnometry, X-Ray Reflectivity, AFM, surface tension and Vickers microhardness measurements. Electron irradiation up to 3.25 GGy induces only small changes of ISG glass structure and macroscopic properties than Au irradiation. Moreover, the magnitude of the changes induced by the sequential irradiation scenario, i.e. electron followed by Au ions, are the same as the one induced by the monobeam irradiation by Au ions, except for the surface tension. Because the bulk damage state are similar, this work demonstrates that there is no coupling between the damage generated by the electron irradiation and the subsequent nuclear collision generated by Au ions. Finally, the hardness and density changes of ISG glass are very similar to those of SON68 glass when submitted to similar irradiation conditions by electron or nuclear collisions. Therefore ISG glass is found to be a good glass surrogate with respect to radiation ageing of the SON68 glass

Etude de la réactivité du dioxyde d'uranium monocristallin vis-à-vis des processus de dissolution en milieu acide : cinétique et réactivité aux interfaces

International audienc

Etude de la réactivité du dioxyde d'uranium monocristallin vis-à-vis des processus de dissolution en milieu acide : cinétique et réactivité aux interfaces

International audienc