Effects of Grain Size on Ultrasonic Attenuation in Type 316L Stainless Steel.

A lead bismuth eutectic (LBE) spallation target will be installed in the Target Test Facility (TEF-T) in the Japan Proton Accelerator Research Complex (J-PARC). The spallation target vessel filled with LBE is made of type 316L stainless steel. However, various damages, such as erosion/corrosion damage and liquid metal embrittlement caused by contact with flowing LBE at high temperature, and irradiation hardening caused by protons and neutrons, may be inflicted on the target vessel, which will deteriorate the steel and might break the vessel.

Suppression of cavitation inception by gas bubble injection: a numerical study focusing on bubble-bubble interaction.

The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in spallation neutron sources, in which liquid mercury is bombarded by a high-power proton beam. In the present paper, we describe numerical investigations of the dynamics of cavitation bubbles in liquid mercury using a multibubble model that takes into account the interaction of a cavitation bubble with preexisting gas bubbles through bubble-radiated pressure waves.

Direct observation and theoretical study of cavitation bubbles in liquid mercury.

The direct observation of cavitation bubbles emerging in liquid mercury under the action of mechanical impacts and theoretical investigations on the experimental results have been made. Through a glass wall, the image of cavitation bubbles appearing near or in contact with the wall was captured by high-speed cameras. Discrepancies found between the bubbles' growth rates determined experimentally and given by a single-bubble theory have been discussed using a theoretical model of Rayleigh-Plesset type that takes into account bubble-bubble and bubble-wall interactions.