Recent studies for structural integrity evaluation and defect inspection of J-PARC spallation neutron source target vessel

Wakui, Takashi  ; Wakai, Eiichi  ; Naoe, Takashi   ; Shintaku, Yohei*; Li, T.*; Murakami, Kazuya*; Kanomata, Kenichi*; Kogawa, Hiroyuki  ; Haga, Katsuhiro  ; Takada, Hiroshi   ; Futakawa, Masatoshi  

The mercury target vessel is designed as multi-walled structure with thin wall (min. 3 mm), and assembled by welding. In order to estimate the structural integrity of the vessel, it is important to measure the defects in welding accurately. For nondestructive tests of the welding, radiographic testing is applicable but it is difficult to detect for some defect shapes. Therefore it is effective to do ultrasonic testing together with it. Because ultrasonic methods prescribed in JIS inspect on the plate with more than 6 mm in thickness, these methods couldn't be applied as the inspection on the vessel with thin walls. In order to develop effective method, we carried out measurements using some testing method on samples with small defect whose size is specified. In the case of the latest phased array method, measured value agreed with actual size. It was found that this method was applicable to detect defects in the thin-walled structure for which accurate inspection was difficult so far.