JRP CALL information
Supported By

European Commission

Short description of the work

The overall goal of the proposed study is to unravel the effects of solute and surface speciation of redox sensitive radionuclide and of the nature of Fe associated to clay minerals on the RN reduction kinetics and efficiency. Structural iron affects the physicochemical properties of clay minerals and, depending on its redox state, may oxidize or reduce radionuclides at their surface thus altering their mobility and/or (bio) availability. The study focuses on a natural montmorillonite (SWa), but also on a nontronite (a Fe rich smectite) interacting with two different radionuclides: Tc and the actinide U. By performing Tc(VII)/U(VI) and Tc(IV) adsorption/reduction experiment on clay samples with increasing levels of reduction, and by combining Tc/U EXAFS analysis and 57Fe Mössbauer analysis to wet chemical analyses (especially Tc/U retention and solid Fe speciation), it is possible to discriminate the contributions of the different mechanisms leading to the overall Tc(VII)/U(VI) adsorption and reduction kinetics. Tc experiments will be a good test to judge if predictive adsorption/reduction model could be established based on the changes of the clay surface properties as a function of pH and redox while U experiments will help to understand the effects of surface and solute speciation changes on redox interactions.

Main visitor contact data
Name: Christophe Tournassat
Organisation: BRGM

JRP Identification
JRP nr: TALI-C03-15
JRP title: Influence of Fe associated to clay minerals on the retention of uranium and technetium: Surface induced redox reactions and kinetics
JRP scope: Scope 2: Actinide in the geological environment

Visited Associated Pooled Facility
Visited APF during the stay: HZDR - ROBL
Name of the APF Contact Person: Andreas Scheinost

Other APF and organisation involved in the JRP
Other organisations involved: PSI-LES (Maria Marques Fernandes); Univ. Bern (Jebril Hadi); UPC (Irene Canals Albiol)
Other APF involved in the project:

Description of the work done at the associated pooled facility
Start date of the stay: 9/26/2015
End date of the stay: 11/13/2015
Quantity of access: 18
Access Unit: Shifts
Misc.: Work during week-ends

Other APF visitors of the JRP during the stay
Visitor 2: Maria Marques Fernandes (PSI-LES)
Visitor 3: Jebril Hadi (Univ. Bern)