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Title: Simplified Reference Electrode for Electrorefining of Spent Nuclear Fuel in High Temperature Molten Salt

Abstract

Pyrochemical processing plays an important role in development of proliferation- resistant nuclear fuel cycles. At the Idaho National Laboratory (INL), a pyrochemical process has been implemented for the treatment of spent fuel from the Experimental Breeder Reactor II (EBR-II) in the last decade. Electrorefining in a high temperature molten salt is considered a signature or central technology in pyroprocessing fuel cycles. Separation of actinides from fission products is being demonstrated by electrorefining the spent fuel in a molten UCl3-LiCl-KCl electrolyte in two engineering scale electrorefiners (ERs). The electrorefining process is current controlled. The reference electrode provides process information through monitoring of the voltage difference between the reference and the anode and cathode electrodes. This information is essential for monitoring the reactions occurring at the electrodes, investigating separation efficiency, controlling the process rate, and determining the process end-point. The original reference electrode has provided good life expectancy and signal stability, but is not easily replaceable. The reference electrode used a vycor-glass ion-permeable membrane containing a high purity silver wire with one end positioned in ~2 grams of LiCl/KCl salt electrolyte with a low concentration (~1%) AgCl. It was, however, a complex assembly requiring specialized skill and talent to fabricate. The constructionmore » involved multiple small pieces, glass joints, ceramic to glass joints, and ceramic to metal joints all assembled in a high purity inert gas environment. As original electrodes reached end-of-life it was uncertain if the skills and knowledge were readily available to successfully fabricate replacements. Experimental work has been conducted to identify a simpler electrode design while retaining the needed long life and signal stability. This improved design, based on an ion-permeable membrane of mullite has been completed. Use of the silver wire and electrolyte composition remains the same. The resulting design maximizes the use of commercial components and can be fabricated with commonly available skills. This has resulted in a significant reduction of effort and cost to fabricate replacements. The piece count requiring assembly in a high purity glove box atmosphere has been reduced by over half and all specialized joints have been eliminated. The new design has been tested in a lab scale electrorefiner and has also been successfully scaled up and installed in the engineering scale electrorefiners.« less

Authors:
;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - NE
OSTI Identifier:
920409
Report Number(s):
INL/CON-07-12259
TRN: US0805566
DOE Contract Number:  
DE-AC07-99ID-13727
Resource Type:
Conference
Resource Relation:
Conference: Global 2007,Boise, Idaho,09/09/2007,09/13/2007
Country of Publication:
United States
Language:
English
Subject:
11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS , 12 - MGMT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; ACTINIDES; ANODES; BREEDER REACTORS; CATHODES; CERAMICS; DESIGN; EFFICIENCY; ELECTRODES; ELECTROLYTES; ELECTROREFINING; FISSION PRODUCTS; FUEL CYCLE; GLASS; MEMBRANES; MOLTEN SALTS; MONITORING; MULLITE; NUCLEAR FUELS; SPENT FUELS; Electrorefining; Molten Salt; Pyroprocessing

Citation Formats

Davies, Kim, and Li, Shelly X. Simplified Reference Electrode for Electrorefining of Spent Nuclear Fuel in High Temperature Molten Salt. United States: N. p., 2007. Web.
Davies, Kim, & Li, Shelly X. Simplified Reference Electrode for Electrorefining of Spent Nuclear Fuel in High Temperature Molten Salt. United States.
Davies, Kim, and Li, Shelly X. Sat . "Simplified Reference Electrode for Electrorefining of Spent Nuclear Fuel in High Temperature Molten Salt". United States. https://www.osti.gov/servlets/purl/920409.
@article{osti_920409,
title = {Simplified Reference Electrode for Electrorefining of Spent Nuclear Fuel in High Temperature Molten Salt},
author = {Davies, Kim and Li, Shelly X},
abstractNote = {Pyrochemical processing plays an important role in development of proliferation- resistant nuclear fuel cycles. At the Idaho National Laboratory (INL), a pyrochemical process has been implemented for the treatment of spent fuel from the Experimental Breeder Reactor II (EBR-II) in the last decade. Electrorefining in a high temperature molten salt is considered a signature or central technology in pyroprocessing fuel cycles. Separation of actinides from fission products is being demonstrated by electrorefining the spent fuel in a molten UCl3-LiCl-KCl electrolyte in two engineering scale electrorefiners (ERs). The electrorefining process is current controlled. The reference electrode provides process information through monitoring of the voltage difference between the reference and the anode and cathode electrodes. This information is essential for monitoring the reactions occurring at the electrodes, investigating separation efficiency, controlling the process rate, and determining the process end-point. The original reference electrode has provided good life expectancy and signal stability, but is not easily replaceable. The reference electrode used a vycor-glass ion-permeable membrane containing a high purity silver wire with one end positioned in ~2 grams of LiCl/KCl salt electrolyte with a low concentration (~1%) AgCl. It was, however, a complex assembly requiring specialized skill and talent to fabricate. The construction involved multiple small pieces, glass joints, ceramic to glass joints, and ceramic to metal joints all assembled in a high purity inert gas environment. As original electrodes reached end-of-life it was uncertain if the skills and knowledge were readily available to successfully fabricate replacements. Experimental work has been conducted to identify a simpler electrode design while retaining the needed long life and signal stability. This improved design, based on an ion-permeable membrane of mullite has been completed. Use of the silver wire and electrolyte composition remains the same. The resulting design maximizes the use of commercial components and can be fabricated with commonly available skills. This has resulted in a significant reduction of effort and cost to fabricate replacements. The piece count requiring assembly in a high purity glove box atmosphere has been reduced by over half and all specialized joints have been eliminated. The new design has been tested in a lab scale electrorefiner and has also been successfully scaled up and installed in the engineering scale electrorefiners.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2007},
month = {9}
}

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