Abstract
In the Molten Salt Reactor (MSR) concept, metal fluorides are key components of possible fuel and coolant salts. The fast reactor option opens the possibility for alternatives to the Li based matrix salts, avoiding the costly 7Li enrichment and the tritium production from residual 6Li. Such alternatives can be based on NaF and KF as matrix components. In this study, two pseudo-binary phase diagrams of NaF-UF4 and KF-UF4, and the NaF-KF-UF4 pseudo-ternary system were experimentally investigated using Differential Scanning Calorimetry (DSC). The obtained data were used to perform a full thermodynamic assessment of the NaF-KF-UF4 system. The calculated pseudo-ternary eutectic was found at 807 K and a 68.9-7.6-23.5 mol% NaF-KF-UF4 composition. The comprehensive experimental and modelling data obtained in this work provide further extension of the JRCMSD thermodynamic database describing thermodynamic properties of key fuel and coolant salts for the MSR technology.
Highlights
In the Generation IV initiative, six advanced nuclear reactors were selected as promising candidates for a future nuclear fleet deployment
The phase equilibria temperatures experimentally obtained in this study by Differential Scanning Calorimetry (DSC) for the NaF-UF4 and KF-UF4 system are presented in Tables 3 and 4 and in Figures 2 and 3, respectively
The type of equilibria were identified by the phase diagram assessment and comparison to earlier studies [15,16]
Summary
In the Generation IV initiative, six advanced nuclear reactors were selected as promising candidates for a future nuclear fleet deployment. The higher alkali fluorides, NaF and KF, might serve as alternative key matrix components of the MSR fuel to replace LiF For this reason, the main focus of this study was to extend the existing JRCMSD thermodynamic database [6] by the full assessment of the NaF-KF-UF4 system. It is possible to predict relevant properties of a multi-component fuel This includes the melting behaviour, which plays a key role for the safety assessment, and in economic aspects of MSRs. It is possible to lower the melting temperature of a possible fuel salt mixture, by using a multicomponent fluoride salt [7,8,9,10]. To obtain the full thermodynamic description of the NaF-KF-UF4 system, thermodynamic optimisations of all related subsystems are necessary
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