JRP CALL information
Supported By

European Commission

Short description of the work

The structures of Tc and Np complexes generated during a reaction between Tc species at selected oxidation states and Np(III and VI) ions have been studied by EXAFS. 9 samples containing a mixture of Tc and Np compounds and a reference sample containing initially Tc(IV) in the presence of nitric acid were prepared at HZDR in Dresden. The Tc K-edge EXAFS spectra were recorded for all solutions using a fluorescence detector. The energy scales for XANES scans for Tc and Np were calibrated with Mo (Mo K-edge at 20000 eV) and Y (Y K-edge at 17038 eV) metals foils, respectively.
The results of the experiments show that in strongly acidic media the pertechnetates are reduced by Np(III) to technetium(III/IV or IV) species while Np(III) ions are transformed not only to Np(IV) but also to Np(VI). Neptunyl(VI) ions are probably generated by a disproportionation of Np(V) ions, the latter species are unstable products of Tc(VII)-Np(III) interaction. In the presence of nitric acid technetium(III/IV or IV) species are completely oxidized to pertechnetates while neptunium is transformed to species with valence states of +4 and +6. An analysis of the oxidation states of neptunium showed that the concentration ratio of Np(VI)/Np(IV) generated during Tc(VII)-Np(III) interaction increases from 0.08 for 0.7M HNO3 to 0.18 for 3M HNO3.
An analysis of the samples containing various concentration of technetium and fixed concentration of neptunium in acidic media confirmed multistep pathway of Tc(red)-Np(ox) interaction. These observations point out to a significant role of Tc(V) and Np(V) in redox chemistry of both elements.

 

Main visitor contact data
Name: Dr Maciej Chotkowski
Organisation: University of Warsaw

JRP Identification
JRP nr: TALI-C05-11
JRP title: Interaction of technetium(III, IV and III,IV) with neptunium in acidic media
JRP scope: Scope 1: Actinide separation chemistry

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

Other APF and organisation involved in the JRP
Other organisations involved:
Other APF involved in the project: HZDR - IRE

Description of the work done at the associated pooled facility
Start date of the stay: 10/2/2015
End date of the stay: 10/6/2015
Quantity of access: 9
Access Unit: Shifts
Misc.: Work during week-ends

Other APF visitors of the JRP during the stay
Visitor 2: Damian Polomski, University of Warsaw