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The corrosion behavior of GH3535 alloys in KCl–MgCl2eutectic salts with or without magnesium (Mg) was investigated using the static immersion tests. The effect of purification treatment on the corrosion of GH3535 specimens was also evaluated by the different analysis. The KCl–MgCl2salts purified with Mg and reducing service temperature can slow down the corrosion rate of GH3535 specimens. Infrared spectra results showed that purification treatment reduced the content of crystal water in the KCl–MgCl2salts. The difference of hydrate content in KCl–MgCl2salts and the diffusion rate of Cr in alloy are the main reasons for the change of GH3535 specimens corrosion rate.

Two kinds of NaCl-KCl-FeCl3eutectic salts were developed based on the thermodynamic calculation and experimental measurement for the low-temperature thermal energy storage. The NaCl-FeCl3and KCl-FeCl3systems were firstly carried out through the CALculation of PHAse Diagrams method, where the calculated values were in excellent agreement with the experimental data. A set of reliable thermodynamic parameter of the NaCl-KCl-FeCl3system was finally obtained. The predicted two eutectic temperature (T = 138.6 °C and T = 140.0 °C) of the NaCl-KCl-FeCl3system are in excellent agreement with the present experimental data (T = 138.2 ± 0.2 °C and T = 140.2 ± 0.3 °C). The actual eutectic points of the NaCl-KCl-FeCl3system are placed at 138.2 ± 0.2 °C &XNaCl = 0.35 mol, XKCl = 0.17 mol, and XFeCl3 = 0.48 mol and 140.2 ± 0.3 °C &XNaCl = 0.34 mol, XKCl = 0.13 mol, and XFeCl3 = 0.53 mol. The fusion enthalpies of the NaCl-KCl-FeCl3system are 70.05 ± 1.18 and 75.18 ± 1.27 J/g, respectively. The average specific heat capacities are 0.80 ± 0.02 J/g·°C and 0.90 ± 0.02 J/g·°C, separately. Their decomposition temperatures are 389.4 ± 0.2 °C and 399.6 ± 0.3 °C. The weight losses are still less than 6 wt% even at 400 °C for 300 h. Two kinds of NaCl-KCl-FeCl3eutectic salts have relatively low melting temperature, good thermal stability, suitable working temperature and low cost, which can be considered as one of the promising candidate thermal energy storage materials.

The corrosion behaviors of 316 stainless steel (316 SS) in NaNO3-NaCl-NaF molten salt and vapor were investigated at 450 °C for 130 h under argon gas and air conditions, respectively. 316 SS suffered from weight gain under the argon gas condition yet experienced weight loss under the air condition. Fe-O enriched layer with different crystal forms (i.e., whisker-like, flake, and grain shapes) was detected by XRD. The crystal forms were relatively homogeneously distributed after the NaNO3-NaCl-NaF molten salt corrosion but were not uniform after the NaNO3-NaCl-NaF vapor corrosion. 316 SS experienced a more serious corrosion attack in salts vapor than that in NaNO3-NaCl-NaF molten salt regardless of the experimental condition. The corresponding corrosion mechanisms were also investigated, and results show that the oxides helped mitigate further corrosion attacks. These findings provide direct guidelines for choosing the appropriate molten salts and alloys for CSP.

FLiNaK (LiF–NaF–KF: 46.5–11.5–42 mol %) is a promising candidate as the secondary loop coolant in molten salt reactor. The thermo-physical properties of pure FLiNaK and FLiNaK containing up to 6000 ppm (equivalent to mg/kg) corrosion product CrF3were measured. The results indicate that the effects of CrF3on melting point, enthalpy, specific heat capacity, density and thermal diffusivity of FLiNaK in liquid state are negligible within the allowable error range, meanwhile the change of thermal diffusivity is significant for FLiNaK in solid state. This work provides fundamental knowledge for the thermo-physical properties of coolant in molten salt reactor.

A comprehensive thermodynamic model of KF-CrF3system was established. The intermediate phases K2Cr5F17, KCrF4, K2CrF5and K3CrF6were described by the stoichiometric compound model and the liquid phase by associated solution model. All the model parameters were optimized by the experimental phase equilibria data assisted by the first-principles prediction within the framework of the calculation of phase diagram(CALPHAD) method. It is demonstrated that the calculated results are fairly consistent with the experimental data, thus we obtained a set of self-consistent and reliable thermodynamic parameters which could well describe the phase equilibria and thermodynamic properties of KF-CrF3 system.

NaNO3-NaCl-NaF salts were investigated by thermodynamic calculation and experimental measurement. A set of self-consistent thermodynamic parameter for the NaNO3-NaCl-NaF salts was finally obtained, by which the predicted melting point (i.e., 288.2 °C) is in excellent agreement with the experimental value (i.e., 288.0 °C). The actual eutectic point of the NaNO3-NaCl-NaF salts is placed at 288.0 °C and XNaNO3 = 0.905 mol, XNaCl = 0.059 mol, and XNaF = 0.036 mol. The fusion enthalpy of the NaNO3-NaCl-NaF salts is 210.0 J/g, and the average liquidus specific heat capacity is 1.760 ± 0.030 J/g·°C. Weight loss is only 5.0 wt% at 650 °C, and its thermal stability is high. The fusion enthalpy is increased by 86.7% than that of NaNO3-KNO3and 252.0% than that of NaNO3-NaNO2-KNO3. Furthermore, the cost of storage solid-liquid phase change heat of the NaNO3-NaCl-NaF salts is only 50% of that of NaNO3-KNO3salt and 25% of that of NaNO3-NaNO2-KNO3salts. The developed NaNO3-NaCl-NaF eutectic salts has relatively superior thermophysical properties, suitable working temperature and good economy performance, and can be used as one of the candidate thermal energy storage fluids. This work provides fundamental reference for the selection of thermal energy storage materials and enriches molten salts databases.

•The latent heat of novel NaF-KCl reciprocal salt is up to 454.8 J/g.•Key thermophysical properties of NaF-KCl were first experimental determined.•Physical property prediction method of reciprocal salts were systematic evaluated.•Cost of per kJ energy of NaF-KCl was 7%-68% lower than that of established molten salts.