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The volumetric properties and the binary diffusion coefficients of liquid sodium–lead alloys in the concentration interval 0–70 at. % Pb


R. Khairulin1, S. Stankus1, O. Yatsuk1 and R. Abdullaev2

1Kutateladze Institute of Thermophysics, Novosibirsk, Russia
2Novosibirsk State University, Russia

Keywords: liquid
property: density, diffusion coefficient
material: sodium–lead alloys

The sodium–lead melts with a low content of Pb are considered as promising heat carriers for fast neutron reactors. However, many thermodynamic and kinetic properties of liquid Na–Pb system are still not sufficiently explored, which considerably hinders an examination of perspectives on the use of these melts as coolants. In this work, the density and the thermal expansion coefficients of liquid sodium and sodium–lead alloys (to X=70 at. % Pb) have been determined using gamma-ray attenuation technique over the temperature range from liquidus line to 950 K. The experimental uncertainty of the density measurements is estimated to be within ± 0.2–0.4 %. Using the obtained results and literature data, the temperature and concentration dependences of the volume properties for Na–Pb system have been constructed. In particular, it has been confirmed that the concentration dependence of the molar volume of the liquid system strongly deviates from the law for ideal solution. Kinetics of homogenisation of the melts with mean composition of 2.5, 5.0, 7.5, 10.0, and 21.0 at. % Pb has been investigated in the temperature range from 550 to 970 K. The measurement technique is based on direct registration of the evolution of composition profile in inhomogeneous liquid sample. The coefficients of binary diffusion D have been derived from these experiments. The experimental uncertainty of the D measurements is estimated to be within ± 10 %. A comparison with literature data [1] has shown that the binary diffusion coefficients for Na-rich melts are about three times greater than the D values for Pb-rich liquid alloys. The behavior of the D(X) dependence confirms a tendency for compound formation, or, in other words, for chemical short-range ordering in the liquid state. We gratefully acknowledge the Russian Foundation for Basic Research (Grant No 09-08-00254) for providing the partial financial support for this research.

References
  1. J.B. Edwards, E.E. Hucke, J.J. Martin, J. Electrochem. Soc. 115, 488 (1968)

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