Failure probability estimation of multi-walled vessels for mercury target

Wakui, Takashi  ; Futakawa, Masatoshi  ; Kogawa, Hiroyuki  ; Ishikura, Shuichi

A liquid mercury target for MW-class pulse spallation neutron sources is being developed. Failure probability analyses on the mercury target that will be installed at the material and life science facility in the Japan Proton Accelerator Research Complex (J-PARC) were carried out taking account of the stress condition caused by various types of loading and material degradation due to neutron irradiation and pitting damages. The mercury target consists of multi-walled vessels; a mercury vessel and a safety hull, to prevent mercury leakage to the outside, i.e. the mercury vessel that is in contact with mercury is covered by the safety hull. The failure probability of the safety hull was estimated to be lower than 10 for the expected designed lifetime. On the other hand, the failure probability of the mercury vessel directly subjected to thermally shocked pressure waves in mercury increased with the operation time and the proton beam power, and was estimated to be ca. 99.9 % for the designed lifetime of the MW-class target.