Abstract

Low-cost benchtop-scale molten fluoride salt cleaning was investigated in FLiBe (LiF-BeF2), focusing on electrochemical cleaning and filtration. FLiBe filtration was demonstrated using both pressurized and open filtration systems. Copper and 400 Monel meshes were effective and reusable. Wetting appears to be the primary obstacle to FLiBe filtration. Oxygen oxidation behavior in FLiBe was examined using cyclic voltammetry (CV) and cyclic square wave voltammetry (CSWV) techniques. Standard addition height measurement was used to determine electrode surface area. Results support a single-step 2-electron process, matching observations in literature. Pt electrodes may be prone to oxidative side reactions, although more investigation is required. Graphite anodes were assessed for oxygen oxidation using CV and chronoamperometry (CA). Results indicated incomplete contaminant reduction and possible carbon contamination. 5.127 grams of powder UF4 was added to 77.717 grams of molten FLiBe, causing bubbling and changing the salt color to green. Subsequent CSWV showed no discernable oxygen peak. We believe the oxygen reacted with trace HF contamination in the UF4 and volatilized as H2O. More testing is required to confirm this. The number of electrons transferred during U+4 oxidation in fluoride salt was estimated using CSWV for the first time. Results ranging from 1.01 to 1.52 support prior theories of a single-electron transfer to U+5. Increased self-dissociation of U+5 to U+6 and U+4 at longer pulse times may occur, although more testing is required. The equilibrium potential of the oxidation of U+4 in FLiBe was measured via CSWV and found to be ~0.3 V more anodic than the equilibrium potential of the O-2/O reaction based on the oxidation limit of the Pt working electrode (WE). Pt WE lifespan was substantially decreased by UF4 oxidation testing.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Chemical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-08-07

Document Type

Thesis

Keywords

nuclear energy, molten salt, MSR, fluoride salt, FLiBe, beryllium, high-temperature ionic liquid, electrochemistry, uranium, oxygen, cyclic voltammetry, square wave voltammetry, FLiBe filtration, 3-electrode cell, uranium pentafluoride, uranium tetrafluoride

Language

english

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