36(f): Development of a Robust Thermodynamic Reference Electrode for Fluoride-based Molten Salt Applications

Problem Statement: The operational lifetime of thermodynamic reference electrodes (TREs) is short in molten salt environments—usually less than 200 hours. One of the main reasons for the short lifetime is that the reference chemistry is not stable. Without a stable TRE, electrochemical measurement techniques are severely limited. Project Approach: AlphaTech Research Corp is proposing the further development of a long-lifetime molten salt TRE (the ARC TRE). The ARC TRE introduces a novel reference chemistry. The ARC TRE has already demonstrated stability for over 1500 hours. The objective for Phase I is to characterize the chemical stability. Phase I Work: There are two major tasks in Phase I: permeability testing of the boron nitride separator and ion-ion stability mechanism testing. TREs will be inserted in between contaminated and clean fluoride salt to determine the permeability of various common constituents through the TRE separator. Other TREs will be inserted into fluoride salt with oxygen contamination and various ratios of ion concentrations. The data analysis methods include ICP-MS and square wave voltammetry. Commercial Application and Benefits: Molten salt is a harsh and aggressive environment with complex chemistry. The redox state of the salt must be monitored for control and material longevity. A TRE can provide knowledge of the redox state, and thus, the development of a stable, long-lifetime reference electrode is essential for nearly any application of molten salt technology. Both the molten salt reactor and pyroprocessing communities are in great need of this product. For example, reference electrodes can be used in important preliminary experimental work that simulates the conditions of a molten salt reactor or to monitor the salt during actual operation. In pyroprocessing efforts, electrochemical monitoring and selectivity are greatly affected by the stability of a reference electrode. The ARC TRE could provide the robust solution needed to enable the deployment of these developing technologies.