Abstract

The temperature dependences of the dynamic viscosity of molten lithium and beryllium fluorides, which are considered as candidate compositions for fuel and coolant of the molten salt reactor (MSR) burner of long-lived actinides from spent nuclear fuel of a VVER 1000/1200 (pressurized water reactor), were obtained by rotational viscometry using an FRS 1600 high-temperature rheometer (Anton Paar, Austria). Molten salt mixtures 0.66LiF–0.34BeF₂ and (0.73LiF–0.27BeF₂) + UF₄ containing 1 and 2 mol % UF₄ were studied with regard to the intermediate and fuel circuits of the MSR. The salt mixtures were prepared by direct melting of components and certified using X-ray phase and elemental analyses. The shear rate parameter was selected according to the viscosity curves obtained in the melts at a temperature of 700°C. It was found that the viscosity does not depend on the shear rate in the range of γ = 6–20 s^–1. When measuring the temperature dependence of viscosity, the γ value was 11 s^–1. The experimentally obtained values of the viscosity of the LiF–BeF₂–UF₄ melts in the temperature range from liquidus to 800°C are described by the linear equation log η = a + b/t, but their temperature coefficients differ noticeably, which indicates a significant dependence of the viscosity of these melts on composition and temperature. The obtained viscosity values for the 0.66LiF–0.34BeF₂ melt agree with the available published data within 7–10% in the temperature range of 650–750°C. With an increase in the LiF content, the viscosity of the melt decreases: it is 20% lower in the 0.73LiF–0.27BeF₂ melt at t = 650°C. However, when 2 mol % UF₄ is added, the viscosity of the fuel salt 0.73LiF–0.27BeF₂ + UF₄ increases by 10% at the same temperature.

中文翻译：

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基于 LiF-BeF2 体系的熔盐粘度

摘要

熔融锂和氟化铍的动态粘度的温度依赖性，它们被认为是熔盐反应堆 (MSR) 燃烧器的燃料和冷却剂的候选成分，该燃烧器来自 VVER 1000/1200（加压）乏核燃料的长寿命锕系元素水反应器），通过使用 FRS 1600 高温流变仪（Anton Paar，Austria）的旋转粘度测定法获得。熔盐混合物 0.66LiF–0.34BeF ₂和 (0.73LiF–0.27BeF ₂ ) + UF ₄含有 1 和 2 mol % UF ₄研究了 MSR 的中间和燃料回路。盐混合物是通过直接熔化组分制备的，并使用 X 射线相和元素分析证明。根据在 700°C 温度下熔体中获得的粘度曲线选择剪切速率参数。^{发现粘度在 γ = 6–20 s –1}范围内不依赖于剪切速率。在测量粘度的温度依赖性时，γ 值为 11 s ^–1。实验获得的 LiF–BeF ₂ –UF ₄熔体在液相线至 800°C 的温度范围内的粘度值由线性方程 log η = a + b / t描述，但它们的温度系数明显不同，这表明这些熔体的粘度对组成和温度有很大的依赖性。获得的 0.66LiF–0.34BeF ₂熔体的粘度值在 650–750°C 的温度范围内与现有公布的数据一致，误差在 7–10% 范围内。随着 LiF 含量的增加，熔体的粘度降低：在t = 650°C时，0.73LiF–0.27BeF ₂熔体的粘度降低 20%。然而，当添加2 mol % UF ₄时，燃料盐0.73LiF–0.27BeF ₂ + UF ₄在相同温度下的粘度增加10%。