Damage inspection of the first mercury target vessel of JSNS

Naoe, Takashi   ; Teshigawara, Makoto   ; Wakui, Takashi  ; Kinoshita, Hidetaka   ; Kogawa, Hiroyuki  ; Haga, Katsuhiro  ; Futakawa, Masatoshi  

A JSNS mercury target vessel composed of type 316L stainless steel suffers radiation damage in the proton and neutron environment. In addition to this damage, the inner wall of the target vessel in contact with mercury is damaged as a result of the cavitation. The target vessel was replaced with a new target in November 2011, because the pneumatic bellows were damaged during the earthquake. Before replacing the target, disk specimens were cut from the beam window of the target vessel in order to investigate the cavitation damage inside the target vessel and to evaluate the change in the mechanical properties due to radiation damage. As a result, it was confirmed that flow-induced erosion damage was not observed on the flow guide. The cavitation damage was concentrated at the center and around both sides approximately 15 mm from the center of the beam window. Based on the detailed measurements, it was concluded that the eroded damage depth of the beam window was 250 m.