1. Introduction 28632. Theoretical Considerations 28643. Electro-deoxidation under Controlled Voltage orPotential 28663.1. Earlier Attempts to Describe the ReductionMechanism 28663.2. Three-Phase Interline (3PI) PropagationModels 28673.3. Alkali Ternary Oxides Intermediates 28673.3.1. Niobium Oxide 28673.3.2. Tantalum Oxide 28683.3.3. Chromium Oxide 28683.3.4. Titanium Oxide 28683.3.5. Zirconium Oxide 28703.3.6. Tungsten Oxide 28703.3.7. Aluminum Oxide 28703.4. Electro-deoxidation of Mixed Oxides andOxide Solid Solutions 28713.5. Attempts to Use Inert Anode 28734. Cyclic Voltammetry 28744.1. Understanding the Cathodic ReductionReactions 28744.2. Determining the Optimum Operation Po-tential 28764.3. Exploring the Surface Phenomenon 28774.4. Studying the Complex Side Processes andDetecting the High Temperature Intermedi-ate Phases 28774.5. Providing Direct Insights into the Kinetics ofElectrode Reactions 28785. Electro-deoxidation under Constant CurrentChronopotentiometry 28796. Summary and Future Direction 2882Author Information 2883Corresponding Author 2883Notes 2883Biographies 2883References 2884

DC Voltammetry of Electro-deoxidation of Solid Oxides

Passive Nondestructive Assay of Nuclear Materials

Electrochemical processing of spent nuclear fuels: An overview of oxide reduction in pyroprocessing technology

Solid state reactions play crucial roles in highly efficient electrochemical energy conversion and storage devices, typically lithium ion batteries and ruthenium oxide supercapacitors. Electrolytic processes may also involve solid-to-solid changes such as the anodisation of metals for designated surface nanostructures and functionalities. More recently, a novel and green route for the production of metals and alloys in molten salts has drawn worldwide attention. It is based on the electro-reduction of metal compounds, particularly oxides, to the respective metals or alloys in the solid-state. This article reviews recent advancement of this new process in terms of potential applications and fundamental understanding.

Solid state reactions: an electrochemical approach in molten salts

Electrochemical reduction behavior of U3O8 powder in a LiCl molten salt

The
electrolytic reduction of U3O8 powder was carried out
using LiCl-Li2O molten salt in a 20-kg U3O8
batch cell to verify the feasibility of the process. As the current passes the
cell, the decomposition of Li2O and the reduction of U3O8
occur simultaneously in a cathode assembly and oxygen gas evolvs at the anode.
The results from a 20-kg U3O8 scale cell were compared
with data obtained from a bench scale cell. The results suggest a successful
demonstration of this process, exhibiting a reduction conversion of U3O8
of more than 99% in a batch.

Electrolytic production of metallic uranium from U3O8 in a 20-kg batch scale reactor

The Advanced Spent Conditioning Process (ACP) developed by the KAERI is based on pyrometallurgy and the electrolytic reduction plays a central role in transforming spent oxide fuels into metals. The constituents of the spent fuels are distributed between a salt and a reduced metal phase during electrolysis. Lithium metal is produced in a molten LiCl-Li2O cell and then it reacts with the metal oxides of the spent fuel producing Li2O and reduced metals. By focusing on the activity of Li2O and the electric potential, the electrolytic reduction process of the ACP is discussed. Thermodynamic considerations are defined and operation conditions are proposed including Li2O activity and cell potential.

Electrolytic reduction of spent oxide fuel in a molten LiCl-Li2O system

Optimization of hybrid-type instrumentation for Pu accountancy of U/TRU ingot in pyroprocessing.

Input nuclear material accountancy is crucial for a pyroprocessing facility safeguards. Until a direct Pu measurement technique is established, an indirect method based on code calculations with burnup measurement and neutron counting for 244Cm could be a practical option. Burnup can be determined by destructive analysis (DA) for final dispositive accuracy or by nondestructive assay (NDA) for near-real time accountancy. In the present study, an underwater burnup measurement system based on gamma-ray spectroscopy with the CZT detector was developed and tested on a spent fuel assembly. Burnup was determined according to the 134Cs/137Cs activity ratio with efficiency correction by Geant4 Monte Carlo simulations. The activity ratio as a function of burnup was obtained by ORIGEN calculations. The measured burnup error was 8.6%, which was within the measurement uncertainty. It is expected that the underwater burnup measurement system could fulfill an important role as a means of near-real time accountancy at a future pyroprocessing facility.

Burnup measurement of spent fuel assembly by CZT-based gamma-ray spectroscopy for input nuclear material accountancy of pyroprocessing

This paper presents results of the first experimental demonstration of the Californium Interrogation Prompt Neutron (CIPN) instrument developed within a multi-year effort launched by the Next Generation Safeguards Initiative Spent Fuel Project of the United States Department of Energy. The goals of this project focused on developing viable non-destructive assay techniques with capabilities to improve an independent verification of spent fuel assembly characteristics. For this purpose, the CIPN instrument combines active and passive neutron interrogation, along with passive gamma-ray measurements, to provide three independent observables. This paper describes the initial feasibility demonstration of the CIPN instrument, which involved measurements of four pressurized-water-reactor spent fuel assemblies with different levels of burnup and two initial enrichments. The measurements were performed at the Post-Irradiation Examination Facility at the Korea Atomic Energy Institute in the Republic of Korea. The key aim of the demonstration was to evaluate CIPN instrument performance under realistic deployment conditions, with the focus on a detailed assessment of systematic uncertainties that are best evaluated experimentally. The measurements revealed good positioning reproducibility, as well as a high degree of insensitivity of the CIPN instrument׳s response to irregularities in a radial burnup profile. Systematic uncertainty of individual CIPN instrument signals due to assembly rotation was found to be <4.5%, even for assemblies with fairly extreme gradients in the radial burnup profile. These features suggest that the CIPN instrument is capable of providing a good representation of assembly average characteristics, independent of assembly orientation in the instrument.

Californium interrogation prompt neutron (CIPN) instrument for non-destructive assay of spent nuclear fuel—Design concept and experimental demonstration

Se-Hwan Park

Papers

Electrolytic production of metallic uranium from U3O8 in a 20-kg batch scale reactor

Electrolytic reduction of spent oxide fuel in a molten LiCl-Li2O system

Optimization of hybrid-type instrumentation for Pu accountancy of U/TRU ingot in pyroprocessing.

Burnup measurement of spent fuel assembly by CZT-based gamma-ray spectroscopy for input nuclear material accountancy of pyroprocessing

Californium interrogation prompt neutron (CIPN) instrument for non-destructive assay of spent nuclear fuel—Design concept and experimental demonstration