The Chemical Treatment of (U, Pu)C Dissolver Solutions as a Preliminary Step for the Purex Reprocessing

Abstract

Oxalic acid constitutes the main interference in the recovery of plutonium from dissolved irradiated carbide fuels by solvent extraction in the Purex process.The effectiveness of various chemical oxidants in the destruction of oxalic acid was investigated.The oxidants were also tested on solutions obtained by dissolving mixed uranium-plutonium carbides in nitric acid.Their effects were evaluated based on the evolution of CO,, on the changes in absorption spectra (400-850 nm) and on the extractability of plutonium with TBP from the resulting solution. Although, none of the chemicals studied were ideally suited, Mn0 2 was the most promising.

Electrochemical behavior of UC in acidic media: Preliminary results

“…The results of MPSC and LV measurements indicate that the electrochemical behavior of UC was similar in the HNO 3 and HClO 4 (0.1-2 M) solutions. In the range of potentials from the open circuit potential to 0.4 V/SCE, the poorly soluble compound (presumably uranium oxycarbide UC x O 1−x ) accumulated at the electrode forms a protective layer.…”

“…However, uranium oxidation was accompanied by the accumulation of undefined organic species in the electrolyte [3,4]. Photochemical [5] and electrochemical [6] techniques were applied to oxidize the organic species to CO 2 and to accelerate UC dissolution.…”

Chemical Head-end Steps for Aqueous Reprocessing of Carbide Fuels

“…Chemical [4 -6], electrochemical [7] and photochemical [8,9] methods have been investigated for this purpose. Flanary et al [4] and Choppin et al [5] investigated the effect of refluxing the dissolver solution as a preliminary step for the preparation of a feed solution suitable for the PUREX process and concluded that it was not possible to prepare a feed solution free from interfering organic species. However, the concentrations of nitric acid used were only 6.7 Μ in the former and 4 Μ in the latter study.…”

“…Flanary et al [4] and Choppin et al [5] studied the effectiveness of various oxidizing agents for the destruction of the organic compounds in the dissolver solutions, and recommended KMn0 4 and Mn0 2 respectively as suitable oxidizing agents. But Mn0 2 was found to adsorb plutonium resulting in its loss.…”

Oxalate Complexation in Dissolved Carbide Systems

“…In this paper we report on studies, whose purpose was to determine which of the organic species were responsible for the interference in the Purex process. A further paper [4] will describe the application of various oxidizing agents for the destruction of such carbonaceous by-products in the dissolver Solution, aiming at the elimination of their adverse effects. Previous papers from this laboratory [5,6] have dealt with other aspects of the head-end treatment of mixed uranium, plutonium carbides dissolved in nitric acid.…”