Visualization of phase distribution in lead-bismuth eutectic during one-dimensional solidification process

伊藤 大介*; 佐藤 博隆*; 齊藤 泰司*; Parker, J. D.*; 篠原 武尚   ; 甲斐 哲也   

Ito, Daisuke*; Sato, Hirotaka*; Saito, Yasushi*; Parker, J. D.*; Shinohara, Takenao; Kai, Tetsuya

Solidification process of lead-bismuth eutectic (LBE) is one of the key phenomena to prevent flow channel blockage accident in an LBE-cooled accelerator-driven system. However, the solidification of liquid metal cannot be observed optically and it is difficult to detect noninvasively. In this study, the one-dimensional solidification process of the LBE was visualized by pulsed neutron transmission imaging. Neutrons have higher transmittivity to the LBE than X-ray and neutron transmission spectrum of the LBE sample can be obtained by pulsed neutron imaging technique. The solid and liquid phases of the LBE were identified during the solidification process by the presence or absence of Bragg edge in the measured neutron transmission spectrum, and the transient behavior of the solid-liquid interface could be visualized. In addition, the characteristic spatial distribution of the crystalline structure was found in Bragg-edge transmission image after the solidification.