Development of repair techniques in the reactor vessel of the experimental fast reactor Joyo; MARICO-2 S/A retrieving

Kaito, Yasuaki; Ashida, Takashi ; Imaizumi, Kazuyuki ; Izawa, Osamu; Naito, Hiroyuki

In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly(S/A) of MARICO-2 (material testing rig with temperature control) had been bent onto the in-vessel storage rack as an obstacle, and the MARICO-2 S/A had been stuck in the transfer pot owing to its deformation. Since the MARICO-2 S/A cannot be retrieved with the existing handling equipment, special handling equipment was developed while considering the anomalous conditions. Emphasis had been placed on (1) how to precisely control the gripper position in the reactor vessel, and (2) how to retrieve the MARICO-2 S/A together with transfer pot with high reliability in the design and development of equipment. The MARICO-2 S/A was retrieved successfully together with transfer pot in 2014. This paper describes the in-vessel repair techniques for MARICO-2 S/A retrieval.