Design and manufacture of Joyo upper core structure for replacement

Ota, Katsu; Ushiki, Hiroshi*; Maeda, Shigetaka   ; Kawahara, Hirotaka ; Takamatsu, Misao ; Kobayashi, Tetsuhiko; Kikuchi, Yuki; Tobita, Shigeharu ; Nagai, Akinori

In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly of "MARICO-2" (material testing rig with temperature control) had bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). The replacement of the UCS was conducted from May to December 2014. The design and manufacture of UCS was started from 2008, and the installation of UCS was completed successfully in November 21th 2014. The major results gained during the design and manufacture of UCS is as follows.