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Title: Electrochemical investigation into the mechanism of plutonium reduction in electrorefining

Abstract

Currently impure plutonium metal is purified at Los Alamos National Laboratory by a molten salt electrorefining process. Electrorefining is an effective method for producing high-purity plutonium metal (> 99.95%). In general this process involves the oxidation of impure plutonium metal from a molten plutonium anode or a solvent metal/plutonium anode, transport of plutonium ions through a molten salt electrolyte, and reduction of the plutonium ions at a tungsten cathode to pure plutonium metal. Purification of the plutonium metal from impurities is based on the difference in free energies of formation between the various metallic impurities associated with plutonium. To obtain a better understanding of the overall electrorefining process and its inefficiencies, an electrochemical investigation into the mechanism for plutonium reduction in a typical electrorefining environment was undertaken. Cyclic voltammetry was selected as the method for determining the electrode mechanism for plutonium reduction at tungsten electrodes. In addition to the standard electrorefining melt (equimolar NaCl-KCl), additional melts that were being investigated in our solvent anode work were also investigated. With insight gained from this investigation, it was hoped that a better selection of electrorefining operating parameters could be obtained.

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (USA)
OSTI Identifier:
6930689
Report Number(s):
CONF-8711195-
Journal ID: CODEN: TANSA; TRN: 88-028492
Resource Type:
Conference
Resource Relation:
Journal Name: Trans. Am. Nucl. Soc.; (United States); Journal Volume: 55; Conference: American Nuclear Society winter meeting, Los Angeles, CA, USA, 15 Nov 1987
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ELECTROREFINING; CHEMICAL REACTION KINETICS; PLUTONIUM; EFFICIENCY; IMPURITIES; LASL; OXIDATION; REDUCTION; RESEARCH PROGRAMS; ACTINIDES; CHEMICAL REACTIONS; ELECTROLYSIS; ELEMENTS; KINETICS; LYSIS; METALS; NATIONAL ORGANIZATIONS; PROCESSING; REACTION KINETICS; REFINING; TRANSURANIUM ELEMENTS; US AEC; US DOE; US ERDA; US ORGANIZATIONS 052001* -- Nuclear Fuels-- Waste Processing

Citation Formats

McCurry, L.E., and Moy, G.M.M.. Electrochemical investigation into the mechanism of plutonium reduction in electrorefining. United States: N. p., 1987. Web.
McCurry, L.E., & Moy, G.M.M.. Electrochemical investigation into the mechanism of plutonium reduction in electrorefining. United States.
McCurry, L.E., and Moy, G.M.M.. 1987. "Electrochemical investigation into the mechanism of plutonium reduction in electrorefining". United States. doi:.
@article{osti_6930689,
title = {Electrochemical investigation into the mechanism of plutonium reduction in electrorefining},
author = {McCurry, L.E. and Moy, G.M.M.},
abstractNote = {Currently impure plutonium metal is purified at Los Alamos National Laboratory by a molten salt electrorefining process. Electrorefining is an effective method for producing high-purity plutonium metal (> 99.95%). In general this process involves the oxidation of impure plutonium metal from a molten plutonium anode or a solvent metal/plutonium anode, transport of plutonium ions through a molten salt electrolyte, and reduction of the plutonium ions at a tungsten cathode to pure plutonium metal. Purification of the plutonium metal from impurities is based on the difference in free energies of formation between the various metallic impurities associated with plutonium. To obtain a better understanding of the overall electrorefining process and its inefficiencies, an electrochemical investigation into the mechanism for plutonium reduction in a typical electrorefining environment was undertaken. Cyclic voltammetry was selected as the method for determining the electrode mechanism for plutonium reduction at tungsten electrodes. In addition to the standard electrorefining melt (equimolar NaCl-KCl), additional melts that were being investigated in our solvent anode work were also investigated. With insight gained from this investigation, it was hoped that a better selection of electrorefining operating parameters could be obtained.},
doi = {},
journal = {Trans. Am. Nucl. Soc.; (United States)},
number = ,
volume = 55,
place = {United States},
year = 1987,
month = 1
}

Conference:
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  • Electrocatalysis for the oxygen reduction reaction (ORR) on five binary Pt alloy electrocatalysts (PtCr/C, PtMn/C, PtFe/C, PtCo/C and PtNi/C) supported on carbon have been investigated. The electrochemical characteristics for ORR in a proton conducting fuel cell environment has been correlated with the electronic and structural parameters determined under in situ conditions using XANES and EXAFS technique respectively. Results indicate that all the alloys possess higher Pt 5d band vacancies as compared to Pt/C. There is also evidence of lattice contraction in the alloys (supported by XRD results). Further, the Pt/C shows increase in Pt 5 d band vacancies during potentialmore » transitions from 0.54 to 0.84 V vs. RHE, which has been ration@ on the basis of OH type adsorption. In contrast to this, the alloys do not exhibit such an enhancement. Detailed EXAFS analysis supports the presence of OH species on Pt/C and its relative absence in the alloys. Correlation of the electrochemical results with bond distances and d-band vacancies show a volcano type behavior with the PtCr/C on top of the curve.« less
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  • They are developing a solvent anode as an alternate method for producing plutonium metal of high purity by an electrorefining process. The goals are to produce metal of 99.98% purity with an anode residue containing less than 2% of the plutonium in the feed material. If they are successful, they will design and demonstrate a system utilizing semi-continuous and remotely controlled operations. Establishing a solvent anode method should lead to improved yields and a substantial reduction in the amount of residues generated by the electrorefining process. The new method should be a viable pyrochemical technique for recovering both plutonium andmore » uranium from spent reactor fuel. Initially, the anode consists of a tantalum rod immersed in a pool of liquid cadmium at 740C. Impure plutonium or a solid anode residue is in contact with the cadmium. As current passes through the anode, plutonium in the cadmium is oxidized and transfers into the molten salt as tripositive plutonium. More plutonium dissolves into the cadmium and the oxidation continues. The tri-positive plutonium is carried through the salt to the cathode, where it is reduced to pure, liquid metal. This metal, which is heavier than the salt, drips from the cathode into an annulus between the anode and cathode compartments and forms a product ring.« less