Pressure wave issues in high power mercury target

A liquid mercury target system for the MW-class pulse spallation neutron source is being developed in the world. Failure probability analysis on the mercury target that will be installed at the material and life science facility in J-PARC was carried out as taking into account the repeatedly loading by pressure waves and material degradation due to pitting and neutron irradiation damages. It was quantitatively evaluated that the failure probability of the safety hull in the target is lower than 10−11 throughout the expected lifetime in design. On the other hand, the failure probability of the mercury vessel directly subject to the pressure waves and the pitting damage increases gradually with proton-beam power and gets to be ca. 99.9% in MW-class target lifetime expected in the design.