Lifetime estimation of mercury target vessel that suffers pitting damage and repeated stress

Wakui, Takashi  ; Hanano, Kohei; Kogawa, Hiroyuki  ; Haga, Katsuhiro  ; Futakawa, Masatoshi  

The high power mercury target for the spallation neutron source is being developed for JSNS. The pulsed proton beams create pressure waves by thermal shock in the mercury. The pressure waves cause stress transients in the mercury vessel and pitting damage on the contact surface with the mercury. The pitting damage on the surface of the mercury vessel influences the fatigue life. The lifetime estimation of the mercury target vessel that suffers pitting damage and repeated stress simultaneously is carried out taking account into account of fatigue crack propagation from multi pits. Probability of fatigue failure in JSNS mercury vessel increased with an increase of the operation time, and was estimated to be ca 0.999 for 2500 hours operation. When failure probability of 0.1 was assumed, the lifetime of the JSNS mercury target was about 270 hours at 1 MW.