JRP 07-21

Partners

FZK

CNRS

FZD

Contact

Prof. Laurent Charlet
Université Joseph Fourrier, CNRS, LGIT, University of Grenoble I / CNRS, LGIT, BP 53, F-38041 Grenoble Cedex France
E-mail e-mail

Reduction of uranium(VI) by adsorbed Fe(II) on several clays and by structural Fe(II) in smectite in O2, CO2 free atmosphere.

Status

 
Terminated - Planned from June 2007 till December 2008

Goals

This project will investigate the possibility of uranium (VI) immobilisation by reduction reaction with various iron(II) species in the structure of clay minerals or adsorbed at their surfaces. In reducing environments, such as radioactive waste repository sites, the following iron species can be encountered: Fe specifically adsorbed on high energy clay surfaces sites (Fe(II)he), Fe exchangeable (Fe(II)ex) and Fe in the structure of clay minerals (Fe(II)str). This project will focus on the analyse of the oxidoreduction reaction between U(VI) and these three iron species: Fe(II)he, Fe(II)ex and (Fe(II)str.

The analysis of oxidoreduction reaction will be performed using methods adapted to the system in consideration and to the species concentrations. In the homogeneous reaction of U(VI) with Fe(II) and in the reference system U(VI) + clay without Fe(II)str, TRLFS will be applied. Uranium and iron oxidation state in heterogeneous reactions will be analysed by combining spectroscopic and chemical methods: wet chemistry for total iron and total uranium in solution , Mössbauer spectrometry for iron speciation using 57Fe as soluble iron species, EXAFS and XANES for uranium and iron speciation.

One step further in the study of the electron pathways, will be performed by analysing the location and the nature of the precipitate oxidoreduction products by AFM.

Expected results

Expected impact on applied issues in the field of nuclear fission energy

The fate of uranium released in the near field and far field will greatly depend on (i) complexation with mobile organic acids (as U(IV)) and carbonate ions (as U(VI)) and (ii) the reaction of U(VI) with Fe+2 released from container corrosion. In a previous work ([3], [2]) we addressed the catalytic effect of iron (III) oxides on the U(VI)-Fe(II) redox reaction. In the present project, we will focus on the catalytic effect of clays.

Expected impact on long term integration

The project supported by ACTINET will allow to improve scientific cooperation between UJF (Prof. L. Charlet, ROBL (Dr. Scheinost), INE (Dr. Bosbach) and FZD Dresden (Dr. Geipel) , LPEC (Dr. Grenèche) in the field of fundamental nuclear geochemistry.

Reports