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Maeda, Shigetaka; Ito, Chikara; Aoyama, Takafumi; Maeda, Yukimoto; Chatani, Keiji
Transactions of the American Nuclear Society, 103(1), p.581 - 582, 2010/11
The experimental fast reactor Joyo of the Japan Atomic Energy Agency is the first liquid sodium fast reactor in Japan. Thirty years of successful operation of Joyo has shown excellent safety and reliability, and has contributed much to the LMFBR development program. Many kinds of irradiation experience have been accumulated to develop the fuels and materials for the prototype reactor Monju and future fast reactors. Accumulated data have been registered with OECD/NEA database with expectation that these data will be widely used. Joyo is presently temporary shutdown because of periodical inspection including in-vessel inspection and repair. After restart, Joyo will play a key role for a wide variety of science and technology fields as fast neutron irradiation bed.
Maeda, Yukimoto; Ito, Chikara; Soga, Tomonori
Transactions of the American Nuclear Society, 102(1), p.742 - 743, 2010/06
The experimental fast reactor Joyo is the first sodium cooled fast reactor in Japan. Irradiation tests in Joyo were commenced from 1983 after the completion of core conversion work from the MK-I breeder core to the MK-II irradiation test bed core. Many valuable irradiation tests were carried out to develop fuels and materials for the prototype fast reactor Monju and a demonstration fast reactor. After the 35 duty cycles operation by the MK-II core, Joyo was upgraded to the high performance MK-III core to increase irradiation capability in 2003. Unique irradiation tests for the FaCT project such as MA bearing MOX fuel and ODS ferritic steel were carried out in the MK-III core. In light of the shutdown of several fast reactors around the world, the ability to make such major contributions to reactor development takes on even greater significance. Irradiation tests in Joyo contribute to the FaCT project, and also to promote the international cooperation such as Generation-IV.
Takamatsu, Misao; Imaizumi, Kazuyuki; Nagai, Akinori; Sekine, Takashi; Maeda, Yukimoto
Journal of Power and Energy Systems (Internet), 4(1), p.113 - 125, 2010/00
During the investigation of an incident that occurred with the experimental fast reactor Joyo, in-vessel observations using a standard Video Camera (VC) and a Radiation-Resistant Fiberscope (RRF) took place at (1) the top of the Sub-Assemblies (S/As) and the In-Vessel Storage rack (IVS), (2) the bottom face of the Upper Core Structure (UCS) under the condition with the level of sodium at -50 mm below the top of the S/As. A simple 6 m overhead view of each S/A, through the fuel handling or inspection holes etc, was photographed using a VC fixed to the rotating-plug with the acrylic panel for making observations of the top of S/As and IVS. About 650 photographs were required to create a composite photograph of the top of the entire S/As and IVS, and a resolution was estimated to be approximately 1 mm. In order to observe the bottom face of the UCS, a remote handling device equipped with RRFs (approximately 13 m long) was specifically developed for Joyo with a tip that could be bent into an L-shape and inserted into the 70 mm gap between the top of the S/As and the bottom of the UCS. A total of about 35,000 photographs were needed for the full investigation. Regarding the resolution, the sodium flow regulating grid of 0.8 mm in thickness could be discriminated, and the base of thermocouple sleeves 6 mm in diameter located 450 mm above the top of S/As were also clearly observed. In both types of observations, it was confirmed that lighting adjustments play a critical role. Particularly in narrow space observations, scattered lighting with automatic dimming controlled light source was available for achieving close observations of the in-vessel structures. In addition to the successful result of the incident investigation, these experiments provided valuable insights for use in further improving and verifying in-vessel observation techniques in sodium cooled fast reactors.
Takamatsu, Misao; Imaizumi, Kazuyuki; Nagai, Akinori; Sekine, Takashi; Maeda, Yukimoto
Proceedings of 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 10 Pages, 2009/07
During the investigation of an incident in Joyo, in-vessel observations using a Video Camera (VC) and a Radiation-Resistant Fiberscope (RRF) took place at (1) the top of the Sub-Assemblies (S/As) and the In-Vessel Storage rack (IVS), (2) the bottom face of the Upper Core Structure (UCS). A simple 6 m overhead view of each S/A was photographed using a VC fixed to the rotating-plug for making observations of the top of S/As and IVS. A resolution was estimated to be approximately 1mm. In order to observe the bottom face of the UCS, a remote handling device equipped with RRFs was specifically developed for Joyo with a tip that can be bent into an L-shape and inserted into the 70 mm gap between the top of the S/As and the bottom of the UCS. The sodium flow regulating grid of 0.8mm in thickness could be discriminated. These experiments provided valuable insights for use in further improving and verifying in-vessel observation techniques in sodium cooled fast reactors.
Itagaki, Wataru; Saito, Takakazu; Imaizumi, Kazuyuki; Nagai, Akinori; Aoyama, Takafumi; Maeda, Yukimoto
Dai-14-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.435 - 438, 2009/06
no abstracts in English
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
Aoyama, Takafumi; Sekine, Takashi; Maeda, Shigetaka; Yoshida, Akihiro; Maeda, Yukimoto; Suzuki, Soju; Takeda, Toshikazu*
Nuclear Engineering and Design, 237(4), p.353 - 368, 2007/02
Times Cited Count：17 Percentile：72.04(Nuclear Science & Technology)Many changes were made in the recent upgrade of the experimental fast reactor JOYO to the MK-III design. The core changes which were made to achieve a fourfold increase in irradiation capacity include the introduction of a second enrichment zone, an increase in core radius and a decrease in core height. Performance tests done at low power, during the rise to power, and at full power, which focus on the neutronics characteristics, are presented. These tests include the nuclear instrumentation system response, the approach to criticality and excess reactivity evaluation, control rod worth calibration, isothermal temperature coefficient evaluation, the calibration of the nuclear instrumentation system with reactor thermal power, and the burn-up reactivity coefficient evaluation. The measurements and comparisons with calculated predictions are shown. The design predictions are consistent with the performance test results, and all technical safety specifications are satisfied. The JOYO MK-III core will provide enhanced irradiation testing capability, as well as serve as a test bed for improving fast reactor operation, performance and safety. Through the performance test evaluation, the core characteristics of a small size sodium cooled fast reactor with a hard neutron spectrum are clarified.
Aoyama, Takafumi; Maeda, Shigetaka; Maeda, Yukimoto; Suzuki, Soju
Journal of Nuclear and Radiochemical Sciences, 6(3), p.279 - 282, 2005/12
The present study examines the potential for the demonstration of fission product transmutation in the experimental fast reactor JOYO at JNC's Oarai Engineering Center. The possibility of creating a highly-efficient transmutation irradiation field by loading neutron moderating subassemblies in the reflector region of JOYO was examined in a series of scoping calculations. A cluster of reflector subassemblies was replaced with beryllium or zirconium hydride (ZrH1.65) moderated subassemblies. These moderated subassemblies surrounded one central test subassembly that would contain 
Tc or 
I target material. The Tc transmutation rate was 16.2% using ZrH
and 13.9% using beryllium as moderator. As a result of this study, basic characteristics of LLFP transmutation in JOYO using relevant moderator materials were investigated and the future feasibility was shown.
Aoyama, Takafumi; Maeda, Shigetaka; Maeda, Yukimoto; Suzuki, Soju
Journal of Nuclear and Radiochemical Sciences, 6(3), p.279 - 282, 2005/12
no abstracts in English
Isozaki, Kazunori; Ogawa, Toru; Nishino, Kazunari; Kaito, Yasuaki; Ichige, Satoshi; Sumino, Kozo; Suto, Masayoshi; Kawahara, Hirotaka; Suzuki, Toshiaki; Takamatsu, Misao; et al.
JNC TN9440 2005-003, 708 Pages, 2005/05
JNC-TN9440-2005-003.pdf:31.46MB
Periodic safety review (Review of the aging management) which consisted of Technical review on aging for the safety related structures, systems and components and Establish a long term maintenance program was carried out up to April 2005.1. Technical review on aging for the safety related structures, systems and components It was technically confirmed to prevent the loss of function of the safety related structures, systems and components due to aging phenomena, which (1) irradiation damage, (2) corrosion, (3) abrasion and erosion, (4) thermal aging, (5) creep and fatigue, (6) Stress Corrosion Cracking, (7) insulation deterioration and (8) general deterioration, under the periodic monitoring or renewal of them 2. Establish a long term maintenance program The long term maintenance program during JPY2005 to 2014 were established based on the technical review on aging for the safety related structures, systems and components. It was evaluated that the inspection or renewal based on the long term maintenance program, in addition to the spontaneous inspection long-term schedule of the long term voluntary inspection plan, could prevent the loss of function of the safety related structures, systems and components in future.
Sekine, Takashi; Maeda, Yukimoto; Aoyama, Takafumi; Ariyoshi, Masahiko
Nihon Genshiryoku Gakkai Wabun Rombunshi, 4(4), p.259 - 275, 2005/04
The MK-III upgrading project was completed in the experimental fast reactor JOYO to increase irradiation capability for irradiation tests. After modification work of cooling system, the system function tests were carried out between August 2001 and March 2003. As a result of these tests, it was confirmed that the performance of whole plant included the modified components, which were the intermediate heat exchanger (IHX) and the dump heat exchanger (DHX) etc., was satisfied with the design. The performance tests were carried out from June 2003 as the last phase of MK-III modification work. During the performance tests, the reactor power was raised step by step as 20%, 50%, 75%, 90% and 100% (140MWt), while confirming the nuclear and thermal characteristics of MK-III core and the heat removal capability of IHX and DHX. All performance tests was successfully carried out and it was confirmed that the performance of JOYO MK-III plant was satisfied with the design. Certificate of pre-use inspection about JOYO MK-III was conferred from Ministry of Education, Culture, Sports, Science and Technology in 27th November 2003 and the MK-III modification work was completed. This report shows the results of the system function tests and the performance tests of JOYO MK-III.
Ito, Chikara; Ito, Hideaki; Ishida, Koichi; Hatoori, Kazuhiro; Oyama, Kazuhiro; Sukegawa, Kazuya*; Murakami, Takanori; Kaito, Yasuaki; Nishino, Kazunari; Aoyama, Takafumi; et al.
JNC TN9410 2005-003, 165 Pages, 2005/03
JNC-TN9410-2005-003.pdf:12.66MB
At experimental fast reactor JOYO, appraisal of detection efficiency of behavior and FFD and FFDL of the fission product which is discharged inside the furnace as one of safety research of the country, is carried out. In MK-II core, the slit in the gas plenum part of the test sub-assembly, the test which irradiates this(1985 April, FFDL in-pile test(I)), providing the slit in the fuel column part of the test sub-assembly, the test which it irradiates(1992 November, FFDL in-pile test(II)) were carried out.MK-III reactor core replacement was completed and started in 2004. That the behavior in the system of FP with the reactor core replacement and so on changes in the MK-III reactor core and to have an influence on the sensitivity and the replying of FFD and FFDL are thought of. Therefore, behavior of FP in the fuel failure in the MK-III reactor core, the performance of FFD and FFDL must be confirmed beforehand. Moreover, to prepare for the fuel failure and the RTCB test which is doing a future plan, and to confirm a plant operation procedure in the fuel failure in MK-III reactor core operation and to attempt for the correspondency to improve are important.Therefore, in the period from 2004 November 11th to November 29th, it carried out the FFDL in-pile(III). It did a series of plant operation to stop a nuclear reactor after loading a reactor core center with the fuel element for the test which provided an artificial slit for the fuel cladding in the MK-III reactor core and irradiating it and detecting fuel damaging and to take out fuel. And it confirmed the operation procedure of the fast reactor in the fuel failure.Also, the improvement items such as the improvement of the operation and the procedure and the remodeling and the service of the facilities could be picked up. In the future, it attempts these compatible, and it prepares for the MK-III reactor core operation and it incorporates a final examination result by the improvement of the safety of FBR.
Maeda, Yukimoto; Kashimura, Yoichi; Suzuki, Toshiaki; Isozaki, Kazunori; Hoshiba, Hideaki; Kitamura, Ryoichi; Nakano, Tomoyuki; Takamatsu, Misao; Sekine, Takashi
JNC TN9440 2005-001, 540 Pages, 2005/02
JNC-TN9440-2005-001.pdf:8.35MB
Periodic safety review (Review of the activity for safety) which consisted of "Comprehensive evaluation of operation experience" and "Incorporation of the latest technical knowledge" was carried out up to January 2005.
Maeda, Yukimoto
2004International Topical Meeting on Operating Nuclear Facility Safety P.217-228, p.217 - 228, 2004/11
None
Maeda, Yukimoto; Aoyama, Takafumi; Yoshida, Akihiro; Sekine, Takashi; Ariyoshi, Masahiko; Ito, Chikara; Masaaki, Nemoto; Murakami, Takanori; Isozaki, Kazunori; Hoshiba, Hideaki; et al.
JNC TN9410 2003-011, 197 Pages, 2004/03
JNC-TN9410-2003-011.pdf:10.26MB
MK-III performance tests began in June 2003 to fully characterize the upgraded core and heat transfer system. Then, the last pre-use inspection was finished in November 2003.This report summarize the result of each performance test.
Sekine, Takashi; Maeda, Shigetaka; Yokoyama, Kenji; Chiba, Go; Aoyama, Takafumi; Maeda, Yukimoto
Saikuru Kiko Giho, (21), 99 Pages, 2004/00
The fast neutron fluence is 1.3 times larger in the JOYO MK-III core than in the MK-II core. To achieve this, the fuel region was expanded and subdivided into two enrichment zones, two of six control rods were shifted from 3rd row to 5th row, and reflector subassemblies were replaced by shielding subassemblies in the outer two rows. To accommodate the resulting 40 % power increase, the sodium coolant flow rate in the primary system was increased from 1100 t/h to 1350 t/h, and the two intermediate heat exchangers and four dump heat exchangers were replaced.MK-III performance tests began in July 2003 to characterize the upgraded core and heat transfer system.As a result of the reactor physics tests at low power, which were completed by early September, it was confirmed that calculation results agreed with the measurements within uncertainties. Thus, the validity of the nuclear design calculation was confirmed.
Takamatsu, Misao; Kono, Naomi; Amezawa, Takayuki; Mitsugi, Takeshi; Maeda, Yukimoto
Saikuru Kiko Giho, (22), p.80 - 82, 2004/00
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.
; Maeda, Yukimoto; Suzuki, Soju; Hara, Hiroshi
Russian Forum for Sci. and Tech. FAST NEUTRON REAC, 0 Pages, 2003/00
The experimental fast reactor JOYO attained its initial criticality in 1977 with the MK-I breeder core. In 1982, JOYO was modified to the MK-II irradiation core and finished its operation in 2000. Throughout the successful operation of MK-I and MK-II core, the net operation time has exceeded 60,000 hours, and experience on the operation, maintenance and core/fuel management of a fast reactor plant has been accumulated. Furthermore the MK-III modification program is underway to improve the irradiation capability of JOYO. When the MK-III core is started, it will support irradiation tests in feasibility studies for fast reactor and related fuel cycle research and development in Japan.
; Yoshida, Akihiro; Aoyama, Takafumi; Maeda, Yukimoto
Saikuru Kiko Giho, (21), p.5 - 25, 2003/00
A Joyo upgrade program named MK-III program was started to develop future FBR in 1987. The main objectives of this program are increasing the capability as an irradiation test bed core and developing innovative FBR technologies.In order to modify the irradiation capability, the core and plant modification program which consists of increasing the neutron flux density of the core, modification of the cooling system, modification of the plant availability factor and upgrading irradiation technologies were decided based on the result s of survey calculations. The licensing work completed in 1995, and all the modification work completed in 2003. JOYO will start rated power operation along with several irradiation tests in 2004. Also the installation and demonstration program of innovative technologies such as Self-actuated shut down system for demonstration FBR and double-walled steam generator for future FBR were investigated.
