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Previously [1], the density of a molten lead-bismuth eutectic was investigated in the range from the melting point of 398.1 K [2] to 726 K. These measurements were performed by the pycnometer method in an experimental facility described in detail in [3]. Because the measuring cell in [1] was made of molybdenum glass, the maximal temperature of these experiments could not exceed 750 K. In order to investigate the thermal properties of a liquid Pb-Bi alloy of eutectic composition at higher temperatures, stainless chrome-nickel steel must be used as the structural material of the working ampoules.At present, the method of γ radiation is used most extensively for measuring the density of metal melts in a wide temperature range. This method was thoroughly developed and described by Stankus and Khairulin, in particular,in [4,5]; in [6], detailed assessment was made of the error of experimental data on the density of liquid metals obtained using this method.Therefore, the method of penetrating γ radiation as interpreted by Stankus [7] was used to investigate the density of molten lead-bismuth eutectic at high temperatures. The working ampoule was made of 12Kh18N10T (chrome-nickel-titanium) stainless steel, and the temperature of the melt in the ampoule was measured by a PP-1 Pt-Pt/Rh thermocouple calibrated by the method of comparison with a standard Pt-Pt + 10%Rh thermocouple. A 137 Cs isotope with an activity of ~2.5×10 11 Bq was used as the radiation source.The Pb-Bi alloy of eutectic composition to be investigated was supplied by the Leipunskii Institute of Energy Physics. It was prepared by the weighing method from highly pure lead and bismuth. Its chemical analysis performed by chelatometry revealed the following content of the main components: 44.5% by mass Pb and 55.5% by mass Bi. The error of this analysis did not exceed ±0.2% by mass. The content of metallic impurities in the investigated alloy was determined by mass spectrometry before and after the experiment. It hardly varied in the course of measurements and did not exceed 1×10 -3 % by mass. This is described in more detail in [1].The content of gas impurities in highly pure lead and bismuth of which the lead-bismuth eutectic was prepared is not regulated by state standards. However, according to the manufacturer of these low-melting metals, the overall content of gas impurities in each of the metals did not exceed 1×10 -3 % by mass.The calculation results showed the correction to density in the presence of the above-identified amounts of metallic and gas impurities to be one or two orders of magnitude less than the error of basic measurements.The investigation of the density of a Pb-Bi alloy of eutectic composition in the liquid state was performed in the temperature range from 404 to 678 K. The measurements were performed with increasing temperature. In so doing, the rate of the melt temperature rise during transition from one temperature level (mode) to another was maintained equal to 1 K/min. HIGH TEMPERATURE Vol. 42 No. 6 2004 1000 STANKUS, KHAIRU...

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