Solubility of Bi in Li-Pb Eutectic Alloy Between 508 and 623 K

Liquid lithium-lead (Li-Pb) eutectic alloy is one of the candidate liquid tritium breeding materials of fusion blanket and it contains bismuth (Bi) as an initial impurity or transmutation product from lead. The saturated solubility of Bi, S (wt.ppm), in Li-Pb was measured in the temperature range from 508 to 623 K. The measured results were plotted on the graph with S (wt.ppm) versus 1/T. From these plots, a positive temperature dependence, where the solubility decreases as the temperature is lowered, is confirmed. The equation of the solubility of Bi in Li-Pb was obtained, too. In addition, the dissolution enthalpy of Bi in Li-Pb, Delta H-sol, was quantified from this equation. The precipitation morphology of Bi in Li-Pb was also investigated. X-ray diffraction was used to analyze the precipitates collected from the surface of the liquid phase. As a result, the peak pattern of Li3Bi was found from the precipitate. Moreover, the amount of polonium produced when the cold trap is introduced to a Li-Pb loop of a fusion reactor was predicted from the solubility obtained in this study.