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Molten salts as heat transfer and storage materials have been used to nuclear energy and concentrated solar power(CSP) applications. In this work, the system of molten salt mixture based on thermodynamic principles was designed as thermal energy storage(TES) materials. The substitutional solution model can be employed to describe the Gibbs energies of all liquid phase. Thermodynamic model parameters for the NaCl-NaNO3-Na2SO4 subsystems were conducted by thermodynamic evaluation and optimization based on experimental phase-equilibria data. Thus, a set of self-consistent thermodynamic database was eventually obtained to reliably calculate the whole phase diagram and thermodynamic properties for the NaCl-NaNO3-Na2SO4 ternary system. The results manifest that the eutectic point of theternary system located at T=280 °C and xNaCl=8.4%, $${x_{NaN{O_3}}}$$ =86.3% and $${x_{N{a_2}S{O_4}}}$$ =5.3%. Moreover, the results predicted were verified experimentally using differential scanning calorimetry(DSC) and the agreement between the measured value[T=(287±2) °C] and predicted value(T=280 °C) was satisfactory. Thus, the thermodynamic calculation method will be used to design and develop novel molten salt mixture as thermal energy storage materials.

The phase diagrams of NaF-BeF2, NaF-ThF4 and NaF-UF4 systems were assessed based on thermodynamic principles, and diverse thermodynamic models were adapted to different systems. Associate solution model (ASM) was used to describe the Gibbs energies of liquid phase of the NaF-BeF2 system, whereas other systems(NaF-ThF4 and NaF-UF4) were treated with the substitutional solution model(SSM) and intermediate compounds were described as stoichiometric compounds according to the Neumann-Kopp rule. All the thermodynamic model parameters were optimized by the least squares procedure until good coincidence was achieved between the calculated results and the experimental data. The derived thermodynamic parameters will be merged into the NaF-BeF2-ThF4-UF4 database to develop the thorium molten salt reactor(TMSR) project.

The effect of CrF3 on the corrosion behaviour of Hastelloy-N and 316L austenitic stainless steel alloys in FLiNaK at 700 °C was investigated using synchrotron radiation and other characterisation techniques. The results showed that CrF3 considerably accelerated the corrosion of both tested alloys by promoting the dissolution of Cr, Fe, and Mn from alloy matrices into molten salt. The 316L stainless steel alloys mainly exhibited intergranular corrosion, whereas the Hastelloy-N alloys tended to exhibit intergranular and pitting corrosion. After corrosion, the lattice parameter of both alloys decreased and Cr1.07Fe18.93 was formed on the surface of the 316L stainless steel alloys.

The suitability of ZrC-SiC-based ceramics was assessed as candidate materials for fluoride. An immersion corrosion with ZrC-SiC composites was performed in molten FLiNaK salts (LiF-NaF-KF: 46.5/11.5/42 mol%) at 850 degrees C. Results indicated that ZrC-SiC-based ceramics were more corrosion resistant than the ZrC ceramic. ZrC-40SiC ceramic exhibited 50% weight-loss to ZrC. This carbide exhibited minimal corrosion attack because of strong resistance to dissolution in molten fluorides. Furthermore, XRD results were consistent with weight-loss and SEM results. The corrosion behavior of ZrC-SiC-based ceramics was affected by impurities, particularly oxygen content. Oxygen and/or oxygen ion participated in corrosion of ceramic. Corrosion of carbide ceramics is mainly due to C4- in ceramics. This ion is oxidized to elemental C by oxidants or impurities in the molten salt. The addition of C may inhibit corrosion of molten salts and thus improve the corrosion resistance of carbide ceramics. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The thermal conductivity of high temperature liquid fluoride salt was measured by laser flash technique for the first time. A graphite crucible was specially designed to exclude the dissolved gas and avoid overflowing of molten salt, meanwhile, a special treat process was used for preparing homogeneous sample. The combined model is feasible for data analysis. The reliability of laser flash method involving crucible structure, sample preparation and data analysis is verified by distilled water and pure KNO3 molten salt. Further, the thermal diffusivity of 46.5 mol%LiF–11.5 mol%NaF–42 mol%KF (FLiNaK) molten salt is determined to be 1.64 × 10−3–2.48 × 10−3 cm2/s at the temperature range of 773–973 K with the blanket atmosphere of helium. Based on specific heat capacity determined by differential scanning calorimetry (DSC) as a constant of 1.88 ± 0.08 J/g K and density measured by our group, the thermal conductivity of FLiNaK molten salt is calculated to be 0.652–0.927 W/m K with the uncertainty of ±0.023 W/m K in the temperature range of 773–973 K.

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 CrF3 were measured. The results indicate that the effects of CrF3 on 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.

Relations of equilibrium phases in the Al-Ca-Li system were calculated by means of the CALPHAD (calculation of phase diagram) method. The reported thermodynamic model parameters for all the constituent binary systems were directly used in the present calculation. A novel thermodynamic description for the three ternary intermetallic compounds(tau (1), tau (2) and tau (3)) was made on the basis of experimental phase equilibria in the Al-Ca-Li system. Comparison between the calculated and experimental phase equilibria shows that we have successfully derived a set of self-consistent thermodynamic parameters for the Al-Ca-Li system. These parameters were then used for the prediction of the selected isothermal and isopleth sections and projected liquidus surface of this ternary system over the entire composition range.