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Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.
Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07
This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.
Ashida, Takashi; Nakamura, Toshiyuki*; Ito, Hideaki
JAEA-Technology 2017-024, 198 Pages, 2017/11
JAEA-Technology-2017-024.pdf:55.8MB
JAEA-Technology-2017-024-appendix(CD-ROM)-1.zip:298.09MBJAEA-Technology-2017-024-appendix(CD-ROM)-2.zip:210.77MB
In the experimental fast reactor Joyo, the disconnecting of an irradiation test subassembly MARICO-2 (Material Testing Irradiation Rig with Temperature Control) from its holding mechanism was conducted in May 2007. After the operation, the rotating plug was rotated despite the fact that the test subassembly was not disconnected completely. Consequently, top of wrapper tube of the MARICO-2 subassembly was bent onto the in-vessel storage rack. Since the overhanging part of the subassembly was in the height in which contacts with the upper core structure, it had damaged the bottom surface of the upper core structure. As the result, it was necessary to replace the damaged upper core structure and to retrieve the bent MARICO-2 subassembly for Joyo restart. Retrieval devices for MARICO-2 subassembly consist of a gripper mechanism to lift subassembly together with transfer pot, a guide tube built-in a pantograph mechanism to adjust lifting axis and safety mechanisms to prevent or mitigate falling of MARICO-2 subassembly, a retrieval cask and so on. Design of the retrieval devices have been verified in ex-vessel partial or full-scale mock-up tests and in-vessel function tests. In 2014, MARICO-2 subassembly was successfully retrieved from the reactor vessel by applying these retrieval devices. Then, retrieved subassembly was transported to a hot-cell facility for post-irradiation examinations. Devices have demonstrated expected performance under the actual environmental conditions of a sodium cooled fast reactor. This is a synthetic report about the retrieval work of the deformed and irradiated test subassembly in Joyo. This report includes the detail design and fabrication of the special retrieval device, results of tests for confirmation including the mock-up tests in manufacturer's factory, and results of MARICO-2 retrieval work from the reactor vessel.
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.
Koga, Kazuhiro*; Ohara, Norikazu*; Ino, Hiroichi*; Kondo, Katsumi*; Ito, Hideaki; Ashida, Takashi; Nakamura, Toshiyuki
FAPIG, (190), p.3 - 8, 2015/07
no abstracts in English
Ashida, Takashi; Miyamoto, Kazuyuki; Okazaki, Yoshihiro*; Ito, Hideaki
JAEA-Technology 2012-047, 106 Pages, 2013/06
JAEA-Technology-2012-047.pdf:11.09MBJAEA-Technology-2012-047-appendix(CD-ROM).zip:15.46MB
In the experimental fast reactor Joyo, failure of disconnecting the irradiation test subassembly MARICO-2 (Material Testing Irradiation Rig with Temperature Control) was occurred and top of the MARICO-2 test subassembly was bent onto the in-vessel storage rack. As a result of this incident, the operation area of rotating plug for the fuel exchange in Joyo is limited. The replacement of the damaged UCS and retrieving the bent MARICO-2 are required to Joyo restoration. This report describes about investigations and some tests to know the status of MARICO-2 test subassembly and the optimized detail design of retrieval device reflecting those results.
Takamatsu, Misao; Ashida, Takashi; Kobayashi, Tetsuhiko; Kawahara, Hirotaka; Ito, Hideaki; Nagai, Akinori
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Safe Technologies and Sustainable Scenarios (FR-13) (USB Flash Drive), 10 Pages, 2013/03
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 bent onto the in-vessel storage rack (IVS) as an obstacle and had damaged the Upper Core Structure (UCS). This incident necessitates the replacement of the UCS and the retrieval of MARICO-2 S/A for Joyo re-start. Along with four stages involving jack-up and retrieval of the existing damaged UCS (ed-UCS), retrieval of the MARICO-2 S/A, and installation of the new UCS (n-UCS) in the restoration work plan, current conditions at Joyo are being carefully investigated, and the results are applied to the designs of special handling equipment, which is being manufactured and scheduled for operation in 2014.
Ito, Hideaki; Ashida, Takashi; Takamatsu, Misao
UTNL-R-0483, p.6_1 - 6_10, 2013/03
no abstracts in English
Ito, Hideaki; Maeda, Shigetaka; Naito, Hiroyuki; Akiyama, Yoichi; Miyamoto, Kazuyuki; Ashida, Takashi; Noguchi, Koichi; Ito, Chikara; Aoyama, Takafumi
JAEA-Technology 2010-049, 129 Pages, 2011/03
JAEA-Technology-2010-049.pdf:6.99MB
The in-vessel gamma dose rate was measured in the experimental fast reactor Joyo to evaluate the activation of reactor structural components and the radiation exposure of the fiber scope used for in-vessel visual inspection. The measurement system, which requires a wide sensitivity range and high durability in a high-temperature environment, was specifically developed for use in the sodium cooled fast reactor. Using this system, the in-vessel gamma dose rate with cooling times of 450 and 720 days after reactor shutdown was measured in Joyo, which has been operated for 71,000 hours over approximately 30 years. The gamma dose rate was calculated using QAD-CGGP2 code with the gamma source intensity obtained by the ORIGEN2 code. The neutron flux used as input to the ORIGEN2 was evaluated by the Joyo dosimetry method. The ratio between the calculated and experimental values ranged from 1.1 to 2.4, confirming the accuracy of gamma dose rate and component activation calculation.
Ito, Chikara; Isozaki, Kazunori; Ashida, Takashi; Sumino, Kozo; Kawahara, Hirotaka
IAEA-TECDOC-1633 (Internet), p.45 - 56, 2009/11
Itagaki, Wataru; Sekine, Takashi; Imaizumi, Kazuyuki; Maeda, Shigetaka; Ashida, Takashi; Takamatsu, Misao; Nagai, Akinori; Maeda, Yukimoto
Proceedings of 1st International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA 2009) (USB Flash Drive), 7 Pages, 2009/06
no abstracts in English
Sumino, Kozo; Isozaki, Kazunori; Ashida, Takashi;
Nuclear Technology, 150(1), p.56 - 66, 2005/04
Times Cited Count：5 Percentile：30.51(Nuclear Science & Technology)Focusing on the cover layer materials (as the Radon Barrier Materials), which could have the effect to restrain the radon from scattering into the air and the effect of the radiation shielding, we produced the radon barrier materials with crude bentonite on an experimental basis, using the rotary type comprehensive unit for grinding and mixing, through which we carried out the evaluation of the characteristics thereof.
Sumino, Kozo; Ashida, Takashi; Kawahara, Hirotaka; Ichige, Satoshi; Isozaki, Kazunori; Nakai, Satoru
Proceedings of Operating Nuclear Facility Safety(2004ONFS),p204-216, p.204 - 216, 2004/11
None
Oshima, Jun; Ashida, Takashi; Isozaki, Kazunori; Sumino, Kozo; Yamaguchi, Akira; Sakaba, Hideo; Ozawa, Kenji; Tomita, Naoki
JNC TN9410 2004-011, 279 Pages, 2004/04
JNC-TN9410-2004-011.pdf:68.76MB
The MK-III project to improve the irradiation capability of the experimental fast reactor JOYO have been carried out since 1987.The increase of fast neutron flux and the enlargement of irradiation field increase the reactor thermal power from 100MWt to 140MWt. To accommodate the increased thermal power,the IHXs and the IHX connecting piping were replaced. The IHXs were replaced with securing cooling system boundary in high dose rate surroundings and very limited operation space of the radiation controlled area in the containment vessel. Primary sodium contains radioactive 22Na,24Na and radioactive CPs such as 60Co and 54Mn,and this sodium adhered to the inner surface of IHXs and pipe. Therefore, the renovation procedure and method were carefully examined based on the JOYO operation and maintenance experiences and research and development results on the sodium handling technique.The major results obtained in the primary heat transport mechanical system (IHXs) renovation operation were shown as follows;
Ishii, Takayuki; Isozaki, Kazunori; Ashida, Takashi; Minakawa, Satoru; Terakado, Tsuguo; Nogami, Hiroshi*; Kakurai, Katsuhiko*; Ueda, Soji*; Kawahara, Hirotaka; Ichige, Satoshi; et al.
JNC TN9410 2002-013, 86 Pages, 2002/11
JNC-TN9410-2002-013.pdf:68.29MB
The MK-III project has been proceeding to improve the irradiation capability of the experimental fast reactor JOY0. The MK-III project has three major purposes such as increase high neutron flux, improvement of plant availability factor and upgrading in irradiation techniques. Thermal output by core transformation for high neutron flux was increased from 100MWt to 140MWt. The main components in the cooling system such as IHX(Intermediate Heat Exchanger) and DHX(Dump Heat Exchanger) were replaced in MK-III modification in order to increase heat removal capability. Heat transfer capacity of IHX was increased from 50MWt/Unit to 70MWt/Unit and that of DHX was increased from 25MWt/Unit to 35MWt/Unit. These components replacement has been safety completed from october 30, 2000 through September 21, 2001. This report summarizes the way, results and safety measures about dismantling of no sodium adhered components and such as DHX blower and sodium cleaning of sodium components such as the DHX, the pipes connected with DHX and secondary side of IHX. Dismantling and sodium cleaning of secondary cooling system components were performed safely and efficiently as almost planned. The total amount of removed sodium was about 13.5kg.
Isozaki, Kazunori; ; Oshima, Jun; ; Ashida, Takashi; Saito, Takakazu; Sumino, Kozo
JNC TN9410 2002-007, 142 Pages, 2002/07
JNC-TN9410-2002-007.pdf:10.92MB
The MK-III Project to improve the irradiation capability of the experimental fast reactor JOYO have been in underway since 1987. The increase of fast neutron flux and the enlargement of that field increase the reactor thermal rate from 100MWt To 140MWt. To increase cooling capacity of heat transport system, intermediate heat exchangers (IHXs), dump heat exchangers (DHXs), piping connecting to IHXs and DHXs, main motors on Primary and secondary main circulation pumps were replaced. The replacement of these large components was carried out under following hard conditions. (1)Limitation of work space, (2)Fuel subassembly and melten sodium in the reactor vessel, (3)high radiation circumstances for primary cooling system, (4)treatment of radioactive sodium (radioactive sodium and corrosion product such as 
CO, 
Mn). There are little experiences of this kind of work in the world. Therefore the organization, workmg plan and safety management points were carefully examined and established, based on the previous experience of JOYO operation and maintenance, research and development results of safety treatment of sodium, experience of previous work on sodium facilities. Following sresults were obtained and effectiveness was confirmed in the work. (1)Development of most suitable working plan derived from elements and full size mock up experiments, reduction of exposure time by workers training, reduction of radiation dose by installation of temporal radiation shielding were useful to reduce radiation dose. The usage of seal bag was useful to prevent the contamination spreading over. (2)The usage of seal bag, oxygen concentration monitoring in the seal bag, nitrogen concentration monitoring in the cooling system cover gas, low pressure control of cover gas were useful to reduce the inflow of oxygen to cooling system. (3)The bite cutting method for piping in air and press down cuttmg by roller cutter in the seal bag to prevent inflow of cutting piece, ...
; Ashida, Takashi; *; *; *; Isozaki, Kazunori;
JNC TN9450 2002-003, 52 Pages, 2002/05
JNC-TN9450-2002-003.pdf:6.24MB
The MK-III project has been proceeding to improve the irradiation capability of the experimental fast reactor JOYO since 1987. The MK-III project has three major purposes such as increasing high neutron flux, improvement of plant availability factor and upgrading in irradiation techniques. The increase of high neutron flux increased thermal output of core from 100MW to 140MW. The main components in the cooling system such as IHXs (Intermediate Heat Exchanger) and DHXs (Dump Heat Exchanger) were replaced in MK-III modification in order to increase heat removal capability. These components replacement has been safely carried out from october 30, 2000 to September 21, 2001. The radioactive corrosion products such as Co and Mn, and radioactive sodium were resided on the inner surface of old IHX which had been already removed from the system in the MK-III modification work. We may dismantle old IHX and remove the residual sodium only after enough decrease of their radioactivity. We have to store it safely over a fairly long Period. Therefore, we examined the safety storage way of old IHX. Based on the examination, we selected the free space inside the pump cleaning pit in the maintenance building as a radioactive waste storage facility. Before the modification work of pump cleaning pit, we needed the permission of design and the construction as well as the change of establishment for installation of radioactive waste storage facility. Modification work of the pump cleaning pit including removal of the interfering pipes were done for two months from April to May, 2000. Enlargement work of opening in pump cleaning pit and coating work of the wall surface were done from August, 2000 to January, 2001. Installation work of the metallic plate for shielding was done for two months from April to May of 2001 after installation of old IHXs in the pump cleaning pit. This report shows the records of installation of radioactive waste storage facility for ...
Ito, Hideaki; Nagai, Akinori; Tobita, Shigeharu; Ashida, Takashi; Kaito, Yasuaki; Katagiri, Genichi*; Kodama, Takemitsu*; Yoshimura, Tetsuji*
no journal, ,
no abstracts in English
dose rate and temperature distribution measurement in the experimental fast reactor JoyoIto, Hideaki; Maeda, Shigetaka; Ito, Chikara; Ashida, Takashi
no journal, ,
no abstracts in English
Okazaki, Yoshihiro; Ashida, Takashi; Miyamoto, Kazuyuki; Kaito, Yasuaki; Ito, Hideaki
no journal, ,
no abstracts in English
Ashida, Takashi; Takamatsu, Misao; Kawahara, Hirotaka; Maeda, Shigetaka; Maeda, Yukimoto; Hara, Masahide*; Kato, Jungo*
no journal, ,
no abstracts in English
