Investigation of the Quasi-Binary Phase Diagram FLiNaK-NdF3

Abstract

The NdF3 solubility in molten eutectic FLiNaK, which is a conceivable medium for a molten salt reactor (MSR), was determined by the quasi-binary phase diagram FLiNaK-NdF3. The eutectic mixture FLiNaK was prepared by direct melting of components LiF, NaF and KF·HF. The acidic anhydrous salt (KF·HF) was used instead of the hygroscopic KF. The NdF3 was sintered by hydrofluorination of Nd2O3. The oxygen impurity in the prepared eutectic FLiNaK, determined by an oxygen analyzer LECO OH836, was 0.036 wt.%, whereas the NdF3 contained 0.04 wt.% of oxygen. A part of the FLiNaK-NdF3 quasi-binary phase diagram was obtained using two thermal analysis techniques: differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The FLiNaK-NdF3 phase diagram in the region of 0–30 mol.% NdF3 contains one eutectic at 2 mol.% NdF3 and 450 °C and two peritectic points: 8 mol.% NdF3 at 500 °C and 22 mol.% NdF3 at 575 °C. The region of the FLiNaK-NdF3 phase diagram below the liquidus line is rather complicated due to the complex structure of the multicomponent system in its molten state, as in its solid state. The NdF3 solubility in FLiNaK is about 5 mol.% at 490 °C and 29 mol.% at 700 °C; this means that the process of the MA transmutation in the MSR can be carried out in molten FLiNaK with a content of actinides as high as 15–20 mol.% in the temperature range of 550–650 °C.

Molecular Dynamics and Experimental Study of the Effect of CeF3 and NdF3 Additives on the Physical Properties of FLiNaK

“…KF·HF decomposes at 673–773 K; the released HF prevents the hydrolysis of salts and simultaneously fluorinates oxygen-containing impurities. The preparation technique is described in detail in our previous work …”

“…The preparation technique is described in detail in our previous work. 53 The neodymium and cerium trifluorides were prepared by hydrofluorination of Nd 2 O 3 and CeO 2 oxides according to the technique described in our previous work. 53 X-ray fluorescence analysis (Rigaku MiniFlex 600) of the obtained samples confirms the presence of NdF 3 and CeF 3 phases only, correspondently.…”

Dynamic Viscosity of the NaF-KF-NdF3 Molten System

“…The mixture was kept at 923 K for at least 2 h. After cooling, the sample was transferred to a glovebox with an inert argon atmosphere. The preparation technique is described in detail elsewhere [ 25 ]. The contents of LiF, NaF and KF in the prepared sample were confirmed by the elemental chemical analysis (Li, Na, K) carried out using ICP-OES (iCAP 6300 Duo, Thermo Scientific, Waltham, MA, USA).…”

“…The neodymium trifluoride (NdF 3 ) was prepared by hydrofluorination of Nd 2 O 3 according to technique described in [ 25 ]. The XRD confirmed the presence of a single hexagonal phase of NdF 3 .…”

Viscosity of fluoride melts promising for molten salt nuclear reactors

“…The NdF3 and CeF3 were prepared by hydrofluorination of their oxides Nd2O3 and CeO2. Techniques for the NdF3 and CeF3 preparation were described in detail elsewhere [18,19]. The obtained products (NdF3 or CeF3) were analyzed by the XRD using a MiniFlex 600 instrument (Japan).…”