Special issue of JNM Study on Phase Transition of Pb-Bi Eutectic Alloy by Neutron Transmission Spectroscopy

LBE (Lead Bismuth Eutectic), which is a candidate for spallation targets, has some problems. One of them is expansion after solidification, which may bring about serious damage of an LBE loop. Two solid phases of β-phase (inter-metallic compound) and γ-phase (solid solution of Pb in Bi) appear in LBE, and it was reported that an increase of the γ-phase observed by X-ray corresponds to the volume expansion of LBE. We performed neutron spectroscopic transmission experiments using a pulsed neutron source in order to observe crystal transformation depending on the position and time for slow and rapid cooling LBE samples. It was found that the crystal structure of the slow cooling LBE varied depending on position while it was rather homogeneous for the rapid cooling sample. The re-crystallization of the γ-phase was more clearly observed for the rapid cooling sample than the slow one. We were able to obtain information of re-crystallization over the whole volume of the samples. 1