JRP CALL information
Supported By

European Commission

Short description of the work
This joint research project has studied Np(V)-U(VI) cation-cation interactions (CCIs) in organic solution (TBP/TPH), which are relevant to solvent reprocessing applications. CCIs are characteristic of pentavalent actinyl ions, and it is thought that the formation of a Np(V)-U(VI) species may synergistically enhance the extraction of Np(V) in the PUREX process, as well as affecting the redox rates of reactions. Spectroscopic techniques (UV-vis-nIR and Raman) available at CEA Marcoule (Atalante) have been used to study organic solutions (TBP/TPH) containing Np(V) in the presence and absence of U(VI). An additional opportunity arose to analyse these organic solutions by EXAFS at the European Synchrotron Radiation Facility. EXAFS data acquired at the ERSF is currently undergoing analysis, which is challenging due to difficulties faced with controlling Np(V) disproportionation (results presented in TALI-C05-01).
UV-vis-nIR spectroscopy results have shown that many different Np(V) species can exist in organic solution, for example Np(V)-TBP, Np(V)-Np(IV)-TBP, Np(V) U(VI)-TBP and possibly Np(V)-U(VI)-DBP depending on the solution conditions. However, for the recorded Raman spectra of Np(V)-, Np(VI) and Np(V)-U(VI) in 30 % TBP, no spectral shift of the Raman bands was observed. The Raman band for NpO2+ may have been observed at 770 cm-1 in 30 % TBP/TPH; however, further Raman spectroscopy must be performed to determine the vibrational bands due to nitrate and TBP. Additionally, more concentrated Np and U solutions in TBP/TPH could be prepared to try to observe the Raman vibrational peaks for the Np(V) U(VI) CCI.

Main visitor contact data
Name: Dr Tamara Griffiths
Organisation: National Nuclear Laboratory

JRP Identification
JRP nr: TALI-C04-18
JRP title: Stability and Structure of Np(V)-U(VI) Cation-Cation Interactions in TBP Organic Phase
JRP scope: Scope 1: Actinide separation chemistry

Visited Associated Pooled Facility
Visited APF during the stay: CEA - ATALANTE
Name of the APF Contact Person: Marie-Christine Charbonnel

Other APF and organisation involved in the JRP
Other organisations involved:
Other APF involved in the project: HZDR - ROBL, NNL - Central Lab

Description of the work done at the associated pooled facility
Start date of the stay: 9/14/2015
End date of the stay: 12/4/2015
Quantity of access: 58
Access Unit: Days