Characterization of a Thermodynamic Reference Electrode for Molten LiF-BeF₂(FLiBe)

Abstract

2LiF-BeF2 (FLiBe) is proposed as coolant for advanced nuclear fission and fusion reactors designs. Electrochemical techniques can be used to answer important research questions about the chemistry, mass transport, and corrosion behavior of FLiBe. The use of electrochemical techniques is predicated upon a thermodynamic reference electrode (RE) for FLiBe. This paper reports the design and characterization of a RE for FLiBe based on the Ni/Ni(II) redox couple, a boron nitride body, and a LaF3 ionic membrane. This electrode, tested in the range of 500°C–600°C shows stability of +/−1 mV for ten hours, good polarizability behavior, and Nernstian behavior. This data is comparable to other RE data reported for other fluoride salt mixtures. This paper also shows that beyond ten hours the RE potential drifts and there is evidence of Ni(II) depletion from the RE. We discuss some of the mechanisms that may cause this drift.

Design and operation of a molten salt electrochemical cell

“…Preventing electroplating beryllium on the platinum wire simplifies the tests and increases the speed of the electrochemical measurements. The electrochemical cell is also designed to house a Ni/Ni(II) thermodynamic reference electrode, designed as described in detail in[ 14 , 15 ].…”

Review—Electrochemical Measurements in Molten Salt Systems: A Guide and Perspective

“…Wang, 10 Park, 11 and Davies 12 investigated novel designs of Ag/AgCl REs enclosed in ceramic and glass tubes. Carotti, 13 Kelleher, 14 Afonichkin, 15 and Klie 16 investigated REs for use in fluoride salt systems proposed for molten salt reactors (MSRs). Bagri 17 investigated a saturated Gd/GdCl 3 RE for thermodynamic measurements of GdCl 3 in LiCl-KCl eutectic salt.…”

Simultaneous measurement of lithium isotope and lithium/beryllium ratios in FLiBe salts using MC-ICP-MS

“…17 Recent papers have used analytical methods for determination of major, minor, and trace element compositions using sophisticated instrumentation designed for trace element analysis. 16,18,19 These methods are suitable for determination of the overall purity of the salts. However, these methods are not ideal for high accuracy Li/Be ratio determinations due to the inherent uncertainties in individual measurements of elemental concentrations.…”