Experimental thermodynamic modelling study of RbF-CeF3 system and its application to the RbF-PuF3 system
Bibliographic record
Abstract
The thermodynamic characterisation of the RbF-PuF 3 system was undertaken using CeF 3 as a non-radioactive surrogate for PuF 3 , a promising candidate fuel component for Molten Salt Reactors (MSRs). The UK's existing plutonium stockpile, if converted to PuF 3 , represents a viable option for molten salt reactor fuels. Incorporating PuF 3 into multicomponent systems may optimise both thermophysical and neutronic properties, making the binary RbF-PuF 3 system a key foundation for more complex fuel salt compositions. Novel DSC data from the RbF-CeF 3 binary, combined with literature sources, enabled a systematic description of phase equilibria across different compositions and temperatures. Particular emphasis was placed on compound purity, phase coexistence, and the use of lightweight custom-designed crucibles, which proved essential for reliable phase diagram reconstruction. In the absence of complete experimental data for intermediate compounds, their thermodynamic properties were estimated using the Neumann–Kopp relation and the CALPHAD method. The liquid phase was described using the Modified Quasichemical Model in the Quadruplet Approximation (MQMQA), applied here for the first time to include liquid complexes of the type [MF 6 ] 3− (M = Ce, Pu). Raman spectroscopy has independently confirmed the presence of these species for M = La and Ce, revealing specific short-range ordering at X(MF 3 ) = 0.33. This structural information serves as an important reference for the reliable optimisation of more complex RbF-MF 3 systems in future thermodynamic modelling. CeF 3 was selected over LaF 3 in this study due to its closer similarity to PuF 3 in melting point, enthalpy of fusion, and ionic radius. Its use revealed eutectics at lower temperatures and higher actinide solubility than comparable AlkF-MF 3 (Alk = Li, Na; M = Ce, Pu) systems. Finally, Rb m M n F 3n+m solid complexes were shown to strongly affect phase behaviour and eutectics, offering greater thermodynamic stability relative to single-eutectic systems such as LiF-PuF 3 and NaF-PuF 3 , albeit with slightly higher melting points. The optimised RbF-PuF 3 liquid solution was further assessed with an Ellingham diagram to evaluate redox potentials and possible corrosion resistance improvements.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".