Short description of the work
The goal of this study was to improve the scientific knowledge of the catalytic phenomenon due to the redox properties of Tc. The role of hydrazinium, hydroxylammonium, U(IV) and Pu(III) were evaluated in both 1.0 M nitric and 1.0 M perchloric acids at room temperature by Uv-Vis spectroscopy for determination of reduced technetium species from pertechnetic acid, Tc(VII). The information obtained from the spectra will be used to choose candidates for XAFS measurements and potential speciation of Tc within these systems.
The reactions performed in 1.0 M perchloric acid initially showed no reduction of pertechnetic acid, Tc(VII) in hydrazinium and hydroxylammonium solutions. The solutions were revisited after 20 days with a noticeable change in absorbance for hydranizium perchlorate solution and an indication of no Tc(VII) remaining in solution with new absorbance peaks at 257 nm and 336 nm. As for the hydroxylammonium perchlorate solution, a small increase in absorbance in the 450-470 nm range(broad) similar to reduced species of Tc within literature but no true species has been assigned.

Reduction of Tc(VII) in 1.0 M nitric acid systems is more rapid than the perchloric acid system. Hydrazinium solutions show fast reaction times of 5 minutes with increasing absorbance(450-470 nm) over several hours. Observation by repeated scans of the hydrazinium nitrate solution over 24 days indicated that the solution contains multiple species of Tc. Similarly to the hydrazinium solution the hydroxylammonium nitrate reduction of Tc(VII) started within a few minutes of mixing resulting in an increasing absorbance at 460-480 nm over 24 hrs. After 20 days the solution contains a different absorbance peak and shape from that of the hydrazinium sample indicating dissimilar Tc complexation.
Uranium (IV) solutions with hydrazinium and hydroxylammonium nitrate in 1.0 M nitric acid were explored. No noticeable reduced Tc species with hydrazinium solution. However, an extremely fast reaction takes place with pertechnetate Tc(VII), U(IV) and hydroxylammonium nitrate showing an increase absorbance at 471 nm. The peak may be due to a reduced Tc species coordinated to uranyl, U(VI). This observation is new and a quick literature review yields no similar information. Reactions with Pu(III) are ongoing with no observable reduction of pertechnetate.
Currently this work has presented five possible candidates containing reduced species of Tc for XAFS measurements.

Main visitor contact data
Name: William Kerlin
Organisation: University of Nevada Las Vegas

JRP Identification
JRP nr: TALI-C05-05
JRP title: Speciation of Technetium in the PUREX Process: Redox Behavior, Hydrolysis, and Complexation
JRP scope: Scope 1: Actinide separation chemistry

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

Other APF and organisation involved in the JRP
Other organisations involved: University of Nevada Las Vegas (Prof. Frederic Poineau)
Other APF involved in the project: CEA - ATALANTE

Description of the work done at the associated pooled facility
Start date of the stay: 10/5/2015
End date of the stay: 12/18/2015
Quantity of access: 37
Access Unit: Days