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

Abstract

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, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> (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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> (wt.ppm) versus 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T$ </tex-math></inline-formula> . 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, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta H_{\mathrm {sol}}$ </tex-math></inline-formula> , 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.