UC Berkeley

This work describes the structure of molten mixtures of lithium fluoride and beryllium fluoride for their relevance to fission reactors and fusion machines, as well as the speciation of chromium in molten fluoride salts more broadly. In an operating molten salt system, a multitude of possible chemical species exist including solvent ions, oxidants from moisture, corrosion products, fission products, and activation products. Describing speciation in the salt entails identification of the possible species (their oxidation states, molecular structures of solvation and corresponding coordination numbers) in which an ion or molecule might exist in the melt. Understanding both solvation structure (first-nearest neighbors, and intermediate-range ordering in the melt) and speciation (oxidation states) is relevant to describing the interaction between the melt and its solutes. In addressing both the structure of LiF-BeF2 solvents (in Chapter 2) and chromium solute speciation (in Chapter 3), this work presents fundamental studies of solvent and solute behavior which are relevant to chemistry control in molten fluoride salt systems, providing novel refinements of the concept of fluoroacidity and broad structural interpretation across temperature and composition. In an attempt to make apparent the understandings of knowledge and engineering held by myself and more broadly in the nuclear engineering community, in the final chapter, I introduce the themes of knowing and being as a nuclear engineer, referring to the nature of engineering knowledge (epistemology) and the core identity of nuclear engineers. This reflexive thinking is made manifest in an embedded-values analysis of core nuclear engineering textbooks. Starting with the premise that epistemological norms affect the practice of engineering, I identify my own understanding of the nature of knowledge as well as trace statements in core textbooks about the role and responsibilities of the nuclear engineer. By reflecting on the conceptualizations of knowledge and identity within the field of nuclear engineering, this chapter presents foundational thought on pioneering the philosophy of nuclear engineering.