FKZr的热物性及热稳定性研究

Experimental investigation on the thermal physical properties and thermal stability of FKZr

熔盐堆冷却剂的热物性是熔盐堆物理、热工水力学设计以及安全分析的重要参数。KF-ZrF4(58-42 mol%)(FKZr)是熔盐堆中的一个具有潜在应用价值的冷却剂。该组成熔盐的热物性在文献中鲜有报道,这为其实际应用带来困难。分别采用差示扫描量热(Differential Scanning Calorimetry,DSC)、阿基米德和热重分析等方法测量和表征了FKZr熔盐的熔点、熔化焓、密度等重要的热物性参数和热稳定性。实验结果表明FKZr的熔点为693.6 K,与文献报道结果一致,符合熔盐堆中冷却剂的要求;熔化焓为71.8 J·g?1;密度为??3.3841?0.8954?10?3T(753?923 K);热重分析表明FKZr在873 K下性质稳定,不发生明显的挥发现象。

Background： Molten fluorides are used as a fuel carrier and coolant in the Molten Salt Reactor（MSR） and have been proposed to be the primary and secondary coolants for Advanced High Temperature Reactor（AHTR） and Very High Temperature Reactor（VHTR） in recent years. KF-ZrF4（58-42 mol%）（FKZr） is of great potential for the above applications. Thermophysical properties of FKZr such as density, liquidus temperature, viscosity, thermal conductivity have important influences on the reactor physics and thermal hydraulic design. Few reports can be found in literature, and obvious discrepancies exist among the data obtained by different researchers. Purpose： On the basis of preparation of qualified FKZr salt, thermophysical properties such as melting point, enthalpy of fusion, density and thermal stability were measured and characterized by experiments. Methods： Differential Scanning Calorimetry（DSC）, Archimedes and thermal gravimetric（TG） were used to measure the melting point, enthalpy of fusion, density and thermal stability of FKZr. Results： The measured melting point of FKZr is 693.6 K which is identical with the results in literature; the enthalpy of fusion is 71.8 J·g·1; the density is p=3.384 1-0.895 4 ×10-3 T（753-923 K） with the uncertainty less than 0.005 g·cm-3; no apparent weightlessness appears below 883 K; at 973 K, the weight loss is about 0.1%, and increases dramatically at 1 053 K. Conclusion： The melting point of FKZr is appropriate as coolant in MSR. FKZr shows good stability and no obvious volatiles below 873 K;but at higher operating temperature, the problems caused by vapor pressure need to be investigated further.