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Takamatsu, Misao; Kawahara, Hirotaka; Ito, Hiromichi; Ushiki, Hiroshi; Suzuki, Nobuhiro; Sasaki, Jun; Ota, Katsu; Okuda, Eiji; Kobayashi, Tetsuhiko; Nagai, Akinori; et al.
Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(1), p.32 - 42, 2016/03
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 been broken and bent onto the in-vessel storage rack as an obstacle and had damaged the upper core structure (UCS). This paper describes the results of the in-vessel repair techniques for UCS replacement, which are developed in Joyo. UCS replacement was successfully completed in 2014. In-vessel repair techniques for sodium cooled fast reactors (SFRs) are important in confirming its safety and integrity. In order to secure the reliability of these techniques, it was necessary to demonstrate the performance under the actual reactor environment with high temperature, high radiation dose and remained sodium. The experience and knowledge gained in UCS replacement provides valuable insights into further improvements for In-vessel repair techniques in SFRs.
Ushiki, Hiroshi*; Okuda, Eiji; Suzuki, Nobuhiro; Takamatsu, Misao; Nagai, Akinori
JAEA-Technology 2015-042, 37 Pages, 2016/02
JAEA-Technology-2015-042.pdf:16.51MB
The reactor vessel of a sodium-cooled fast reactor (SFR) is filled with sodium coolant and cover gas (argon gas). In case of a cover gas boundary open (ie., in-vessel repair), installation of a temporary cover gas boundary and controlling the cover gas pressure slightly positive are required to prevent the cover gas release and the contamination of impurities, and during upper core structure (UCS) replacement in the experimental SFR Joyo from March to December 2014, a vinyl bag was installed as a part of the temporary cover gas boundary. However, because it has inferior thermal resistance, supply a cooling gas too much was required to maintain proper temperature for two months. On the basis of this requirement, a cover gas recycling system with precise pressure control was developed and adopted for UCS replacement. The system has a good pressure controllability and recyclability. The successful results of this system contributed to the certain promotion of UCS replacement. In addition, the insights and the experience gathered in this development are expected to improve the in-vessel repair techniques in sodium-cooled fast reactors.
Ota, Katsu; Ushiki, Hiroshi*; Maeda, Shigetaka; Kawahara, Hirotaka; Takamatsu, Misao; Kobayashi, Tetsuhiko; Kikuchi, Yuki; Tobita, Shigeharu; Nagai, Akinori
JAEA-Technology 2015-026, 180 Pages, 2015/11
JAEA-Technology-2015-026.pdf:79.87MB
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.
Yasuda, Ryo; Iikura, Hiroshi; Matsubayashi, Masahito; Kajiwara, Kenichi*; Kagawa, Hideshi*; Kushiki, Kenichi*; Nagata, Yasuichi*
no journal, ,
In a recent year, many researchers and engineers in industrial fields have used TNRF in JRR-3 for their experiments. Such promotion of the industrial use is attributed to program of MEXT called as trial-use and establishing a system of which visitors could easily use several facilities in JAEA. From those industrial uses, some technological developments such as improvement of spatial resolution are required in TNRF. In this report, we would state detailed information about the current situation of research fields and main course of technological developments in TNRF.
Ushiki, Hiroshi; Ito, Hiromichi; Okuda, Eiji; Suzuki, Nobuhiro; Sasaki, Jun; Ota, Katsu; Kawahara, Hirotaka; Takamatsu, Misao; Nagai, Akinori; Okawa, Toshikatsu
no journal, ,
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) in 2007. As a part of the restoration work, UCS replacement was begun at March 24, 2014 and was completed at December 17. In-vessel repair (including observation) for sodium-cooled fast reactors (SFRs) is distinct from that for light water reactors and necessitates independent development. Application of developed in-vessel repair techniques to operation and maintenance of SFRs enhanced their safety and integrity. There is little UCS replacement experience in the world and this experience and insights, which were accumulated in the replacement work of in-vessel large sturucture (UCS) used for more than 30 years, are expected to improve the in-vessel repair techniques in SFRs.
Kawamura, Masaya*; Ushiki, Hiroshi*; Enuma, Yasuhiro; Futagami, Satoshi; Ogumo, Shinya*; Ichihara, Takashi*; Nakashima, Takashi*
no journal, ,
no abstracts in English
Kanda, Hironori; Enuma, Yasuhiro; Futagami, Satoshi; Chikazawa, Yoshitaka; Okano, Yasushi; Yoshioka, Naoki*; Ushiki, Hiroshi*
no journal, ,
Safety measures against sodium-water reaction have been discussed in Safety Design Guideline of GIF. In this study, redundancy and diversity of the design measures for steam generators were enhanced and consequences of multiple failures of the mitigation measures was assessed.
Kanda, Hironori; Enuma, Yasuhiro; Futagami, Satoshi; Kawamura, Masaya*; Ushiki, Hiroshi*; Ogumo, Shinya*; Ichihara, Takashi*; Nakashima, Takashi*
no journal, ,
Ota, Katsu; Ito, Hiromichi; Ushiki, Hiroshi; Yoshihara, Shizuya; Tobita, Shigeharu; Kawahara, Hirotaka; Hara, Masahide*; Okazaki, Hiroyoshi*; Tanaka, Junya*; Tatsuno, Takahiro*
no journal, ,
no abstracts in English
Okuda, Eiji; Ushiki, Hiroshi; Suzuki, Nobuhiro; Sasaki, Jun; Takamatsu, Misao
no journal, ,
no abstracts in English
Amano, Katsunori; Enuma, Yasuhiro; Futagami, Satoshi; Ushiki, Hiroshi*; Kawamura, Masaya*; Ichihara, Takashi*
no journal, ,
no abstracts in English
