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Naoe, Takashi; Kinoshita, Hidetaka; Wakui, Takashi; Kogawa, Hiroyuki; Haga, Katsuhiro; Takada, Hiroshi
no journal, ,
A liquid mercury target system for the spallation neutron source has been in operation at J-PARC. In the mercury target, pressure waves are generated due to abrupt heat deposition by the proton beam injection, inducing cavitation. A 3-mm-thick beam window portion of the enclosure vessel made of 316L stainless steel, so-called target vessel, is severely damaged by the cavitation. To observe the cavitation damage inside the target vessel, the beam window was cut out with an annular cutter. In 2017, some tests were conducted to optimize cutting conditions for cutting out a sample from the target No.2. As a result, the cutting was smoothly done with a water soluble lubricant. Since dose rate of the sample was extremely high for direct observation with a microscope, a replica method was adopted to observe the cavitation damage on the cut specimen. In the presentation, progress in the beam window cutting and cavitation damage observation by remote handling will be reported.
Kinoshita, Hidetaka; Haga, Katsuhiro; Kai, Tetsuya; Wakui, Takashi; Kogawa, Hiroyuki; Teshigawara, Makoto; Naoe, Takashi; Takada, Hiroshi
no journal, ,
At the J-PARC, a mercury target system has been in operation as a neutron production target of the spallation neutron source driven by 3-GeV protons. It is loaded on a big target trolley (L12 W2.6 H4 m) which moves horizontally on a rail in a hot cell. The volume of the hot cell is as large as L43 W12 H15 m. Target vessel replacement is performed with full-remote handling devices such as a 6-axis power manipulator, 3 pairs of master/slave manipulators, an in-cell overhead 20 t crane and radiation resistant cameras. Since a large amount of radioactive gaseous nuclides are generated in mercury via the spallation reactions, the off-gas processing system is installed in a room nearby the hot cell to transfer the cover gas in a serge tank of the mercury circulation system to the off-gas processing system before replacing target vessel. More detailed design of hot cell and experiences on the target system maintenance will be presented.