Liquid Pb–Bi eutectic alloy is a good candidate as a coolant and neutron spallation source for the development of new accelerators driven system, one of the possible solutions for the nuclear waste problem, but liquid metal corrosion and embrittlement are the main issue.
The structure of the liquid alloy is not stable but undergoes relevant changes as the temperature increases (elemental clustering). To understand transformations occurring in the liquid state, the alloy has been water quenched from the liquid at different temperature. SPEM results evidenced a structural and microchemical rearrangement of the atoms in the melt consisting in the evolution of cluster size and composition.

The distribution of the two metals is characterized by the following: (i) Pb-enriched clusters, (ii) Bi-enriched clusters and (iii) a matrix in near eutectic composition. The average size of clusters is reduced by increasing temperature: it is in the range of 1 ÷ 3 μm at 313 °C and passes to 0.5 ÷ 0.9 μm at 518 °C.