Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Ashida, Takashi; Ito, Hideaki; Miyamoto, Kazuyuki*; Nakamura, Toshiyuki; Koga, Kazuhiro*; Ohara, Norikazu*; Ino, Hiroichi*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(4), p.210 - 222, 2016/12
In the experimental fast reactor Joyo, it was confirmed that the top of the irradiation test sub-assembly of material testing rig named "MARICO-2" had been broken and bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). As the result, for Joyo restart, it was necessary to replace the damaged UCS and to retrieve the bent sub-assembly. This paper describes in-vessel repair techniques performed in the retrieval work of the obstacle inside of the reactor vessel. The devices which were prepared for this work demonstrated expected performance under the environmental conditions of an SFR such as high temperature and radiation dose, and the work was completed in 2014. The successful operation of this retrieval work of the damaged component inside of a reactor vessel will contribute to the development of in-service inspections and repair technics in an SFR.
Okuda, Eiji; Sasaki, Jun; Suzuki, Nobuhiro; Takamatsu, Misao; Nagai, Akinori
JAEA-Technology 2016-017, 20 Pages, 2016/07
JAEA-Technology-2016-017.pdf:5.75MB
In-Vessel Observation (IVO) techniques for Sodium Cooled Fast Reactors (SFRs) in service are important for confirming their safety and integrity. Since IVO equipment for an SFR has to be designed to tolerate the severe conditions (high temperature, high radiation dose and limited access route), fiberscopes used to be used in previous IVO for SFRs. However, in order to attain an IVO with higher quality and resolution, IVO using a radiation resistant camera was conducted in the fast experimental reactor Joyo and obtained some results. The demonstration results provided valuable insights for use in further improving and verifying IVO techniques in SFRs.
Ashida, Takashi; Takamatsu, Misao; Ito, Hideaki; Okawa, Toshikatsu; Yoshihara, Shizuya
no journal, ,
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 broken and bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). This incident necessitated the replacement of the UCS and the retrieval of the MARICO-2 sub-assembly for Joyo restoration. This paper describes the summary of Joyo restoration works. In-vessel repair techniques for sodium cooled fast reactors (SFRs) are important in confirming safety and integrity of SFRs. However, the demonstrated techniques under the actual reactor environment with high temperature, high radiation dose and remaining sodium are not enough to secure the reliability of these techniques. The experience and knowledge accumulated in the UCS replacement provides valuable insights into further improvements for in-vessel repair techniques in SFRs.
Emura, Yuki; Kamiyama, Kenji; Matsuba, Kenichi; Isozaki, Mikio
no journal, ,
In case of core disruptive accident in sodium-cooled fast reactors, it is thought that molten-core material will be discharged into the lower plenum and fragmented there due to fuel-coolant interactions. To understand this fragmentation behavior, we performed the simulation test in which molten stainless steel discharged into sodium pool and fragmentation behavior was observed using a visualization system combined X-ray and high-speed camera. Both successful visualization of fragmentation behavior by above visualization system and rapid cooling of molten stainless steel due to fragmentation are presented in this study.
Suzuki, Masaaki*; Ito, Mari*; Hashidate, Ryuta; Takahashi, Keita; Yada, Hiroki; Takaya, Shigeru
no journal, ,
Maintenance scheduling is typically performed manually, which is a time- and resource-consuming process due to the many components and constraints that must be considered. Besides, to develop next-generation power plants with excellent operability, it is necessary to make it possible to evaluate maintainability in advance at the design stage. Thus, this paper proposes a maintenance-scheduling model based on swarm intelligence to develop an automatic scheduling system for addressing the inspection process scheduling problem in a SFR plant.
