Effect evaluation of partial termination of local sampling system in Hot Laboratory at Oarai Nuclear Engineering Institute; Airflow analysis on diffusion of radioactive material

Fukui, Makoto; Chizuwa, Shingo*; Kikuchi, Norihiro; Tanaka, Masaaki; Hashimoto, Makoto

JAEA-Review 2025-045, 42 Pages, 2025/12

JAEA-Review-2025-045.pdf:2.95MB

Hot laboratory (HL) at Oarai Nuclear Engineering Institute is a facility that conducts post-irradiation testing of fuel samples and reactor materials in hot cells. A set of local sampling system (LSS) is installed as a radiation control equipment to monitor the concentration of radioactive materials in the air in work environment. The LSS of HL equipped 23 sampling points, which are called as local sampling ends (LSE). It was recognized that air sampling had not operated at some of the LSE, and the concentration of radioactive materials in the air was not measured as prescribed. In this report, we evaluated the effect of partial termination of the LSS and the resulting increase in sampling intervals on the control of radioactive material concentrations in the air using airflow analysis assuming the diffusion of radioactive materials from hot cells in the controlled area of HL. The Service Area of the HL, where 10 LSEs were set in a wide area, was selected as an evaluation area. Airflow analysis including the diffusion of virtual contaminant particles was conducted on the evaluation area. Diffusion of virtual contaminants from hot cells and sampling of virtual contaminants at LSEs are simulated in the case of LSS in fully working and LSS with termination of 4 LSEs. The evaluation results showed that the effect of the partial termination of LSS and the resulting increase in sampling intervals on the control of the concentration of radioactive materials in the air are small.

Monitoring of airborne C discharge at RI facilities; A Comparison of collection and oxidation methods

Ueno, Yumi; Koarashi, Jun; Iwai, Yasunori; Sato, Junya; Takahashi, Teruhiko; Sawahata, Katsunori; Sekita, Tsutomu; Kobayashi, Makoto; Tsunoda, Masahiko; Kikuchi, Masamitsu

Hoken Butsuri, 49(1), p.39 - 44, 2014/03

http://doi.org/10.5453/jhps.49.39

http://doi.org/10.5453/jhps.49.2

The Japan Atomic Energy Agency has conducted a monthly monitoring of airborne C discharge at the forth research building (RI facility) of the Tokai Research and Development Center. In the current monitoring, C, which exists in various chemical forms in airborne effluent, is converted into CO with CuO catalyst and then collected using monoethanolamine (MEA) as CO absorbent. However, this collection method has some issues on safety management because the CuO catalyst requires a high heating temperature (600C) to ensure a high oxidation efficiency and the MEA is specified as a poisonous and deleterious substance. To establish a safer, manageable and reliable method for monitoring airborne C discharge, we examined collection methods that use different CO absorbents (MEA and Carbo-Sorb E) and oxidation catalysts (CuO, Pt/Alumina and Pd/ZrO). The results showed 100% CO collection efficiency of MEA during a 30-day sampling period under the condition tested. In contrast, Carbo-Sorb E was found to be unsuitable for the monthly-long CO collection because of its high volatile nature. Among the oxidation catalysts, the Pd/ZrO showed the highest oxidation efficiency for CH at a lower temperature.

Mock-up test results of monoblock-type CFC divertor armor for JT-60SA

Higashijima, Satoru; Sakurai, Shinji; Suzuki, Satoshi; Yokoyama, Kenji; Kashiwa, Yoshitoshi; Masaki, Kei; Shibama, Yusuke; Takechi, Manabu; Shibanuma, Kiyoshi; Sakasai, Akira; et al.

Fusion Engineering and Design, 84(2-6), p.949 - 952, 2009/06

https://doi.org/10.1016/j.fusengdes.2009.02.021

An upgrading device of JT-60 tokamak with fully superconducting coils (JT-60SA) is constructed under both the Japanese domestic program and the international program "Broader Approach". The maximum heat flux to JT-60SA divertor is estimated to 15 MW/m for 100 s, and a monoblock-type CFC divertor armor is promising. The JT-60SA armor consists of CFC monoblocks, a cooling CuCrZr screw-tube, and a thin OFHC-Cu buffer layer, and the brazed joints are essential for the armor. Metalization inside CFC monoblock is applied for further improvement, and we confirmed again that the mock-up has heat removal capability in excess of ITER requirement. For optimization of the fabrication method and understanding of the production yield, the mock-ups corresponding to quantity produced in one furnace is also produced, and the half of the mock-ups could remove 15 MW/m as required. This summarizes the recent progress of design and mock-up test results for JT-60SA divertor armor.

Conceptual design of superconducting magnet system for JT-60SA

Yoshida, Kiyoshi; Kizu, Kaname; Tsuchiya, Katsuhiko; Tamai, Hiroshi; Matsukawa, Makoto; Kikuchi, Mitsuru; della Corte, A.*; Muzzi, L.*; Turt, S.*; Di Zenobio, A.*; et al.

IEEE Transactions on Applied Superconductivity, 18(2), p.441 - 446, 2008/06

https://doi.org/10.1109/TASC.2008.921970

The upgrade of JT-60U magnet system to superconducting coils (JT-60SA) has been decided by both parties of Japan and EU in the framework of the Broader Approach agreement. The magnet system for JT-60SA consists of 18 toroidal field (TF) coils, a central solenoid (CS) with four modules, seven equilibrium field (EF) coils. TF case encloses the winding pack and is the main structural component. CS consists of four winding pack modules with its pre-load structure. Seven EF coils are attached to the TF coil cases through supports which include flexible plates. Since CS modules are operated at high magnetic field, NbSn superconductor is used. While NbTi superconductor is used in TF coils and EF coils. The magnet system has large heat load from nuclear heating by DD fusion and large AC loss from control actions. This paper descries the technical requirements, the operational interface and the conceptual design of the superconducting magnet system for JT-60SA.

Feasibility of lead-bismuth-cooled accelerator-driven system for minor-actinide transmutation

Tsujimoto, Kazufumi; Oigawa, Hiroyuki; Kikuchi, Kenji; Kurata, Yuji; Mizumoto, Motoharu; Sasa, Toshinobu; Saito, Shigeru; Nishihara, Kenji; Umeno, Makoto*; Takei, Hayanori

Nuclear Technology, 161(3), p.315 - 328, 2008/03

https://doi.org/10.13182/NT08-A3929

Feasibility was discussed for lead-bismuth cooled accelerator-driven system (ADS) to transmute minor actinides partitioned from high-level radioactive waste. Since lead-bismuth will cause considerable corrosion and erosion effects at high temperature, the fuel clad temperature must be kept as low as possible. Moreover, the most critical issue of ADS design is engineering viability of the high-power spallation target and the beam window. Thermal-hydraulic and structural analysis was carried out for both the fuel assembly and the beam window. In addition to the analysis in steady state, transient behaviors were also studied during typical transient and unprotected accidents. The results showed that engineering viability is reasonably achievable in nominal operation. For beam trip which will be the most frequent transient, the number of events to cause the failure of the beam window is estimated as more than . For safety aspects of ADS during unprotected accidents, estimated results showed that ULOF would cause the most significant problem, if beam operation was kept. Therefore, high reliability of the beam shutdown is required for the ADS safety.

Prospective performances in JT-60SA towards the ITER and DEMO relevant plasmas

Tamai, Hiroshi; Fujita, Takaaki; Kikuchi, Mitsuru; Kizu, Kaname; Kurita, Genichi; Masaki, Kei; Matsukawa, Makoto; Miura, Yukitoshi; Sakurai, Shinji; Sukegawa, Atsuhiko; et al.

Fusion Engineering and Design, 82(5-14), p.541 - 547, 2007/10

https://doi.org/10.1016/j.fusengdes.2007.07.019

JT-60SA is positioned as the ITER satellite tokamak to conduct research elements to support and supplement ITER towards DEMO under the joint collaboration of Japan and EU. After the discussions in JA-EU Satellite Tokamak Working Group in 2005, the heating power is increased up to 41MW, 100s to ensure the ITER support research. With such increased heating power, the prospective plasma performances are analysed by the equilibrium and transport analysis codes. Operation window of a fully non-inductive current drive is extended to high density region. Simultaneous achievement of high equivalent Q and high normalised beta is also expected in wide operational margin. Those prospects strongly indicate that JT-60SA is suitable machine to conduct the advanced research orienting to ITER and DEMO.

Conceptual design of magnet system for JT-60 super advanced (JT-60SA)

Kizu, Kaname; Tsuchiya, Katsuhiko; Ando, Toshinari*; Sborchia, C.*; Masaki, Kei; Sakurai, Shinji; Sukegawa, Atsuhiko; Tamai, Hiroshi; Fujita, Takaaki; Matsukawa, Makoto; et al.

IEEE Transactions on Applied Superconductivity, 17(2), p.1348 - 1352, 2007/06

https://doi.org/10.1109/TASC.2007.898966

no abstracts in English

Tokamak and spherical tokamak research in Japan

Takase, Yuichi*; Kikuchi, Mitsuru; Maekawa, Takashi*; Matsukawa, Makoto; Nagata, Masayoshi*; Nishio, Satoshi; Ono, Yasushi*; Sato, Konosuke*; Tobita, Kenji

Fusion Science and Technology, 51(2T), p.46 - 51, 2007/02

https://doi.org/10.13182/FST07-A1311

Japanese tokamak and spherical tokamak (ST) research programs are described. Tokamak research will focus on steady state high( = 3.5-5.5) research on JT-60SA (formerly NCT) in support of ITER and DEMO. JT-60SA will also serve as the Satellite Tokamak under the JA-EU Broader Approach framework. ST research has been reorganized as the All-Japan ST Research Program, aiming for creative and innovative research focused on ultra-high and ultra-long pulse regimes. Results of plasma start-up, RF heating, and plasma merging reconnection experiments are summarized. Prospects of contribution of low aspect ratio tokamaks to fusion energy development, are presented.

Development of aluminum (Al5083)-clad ternary Ag-In-Cd alloy for JSNS decoupled moderator

Teshigawara, Makoto; Harada, Masahide; Saito, Shigeru; Oikawa, Kenichi; Maekawa, Fujio; Futakawa, Masatoshi; Kikuchi, Kenji; Kato, Takashi; Ikeda, Yujiro; Naoe, Takashi*; et al.

Journal of Nuclear Materials, 356(1-3), p.300 - 307, 2006/09

https://doi.org/10.1016/j.jnucmat.2006.05.017

We adopted silver-indium-cadmium (Ag-In-Cd) alloy as a material of decoupler for decoupled moderator in JSNS. However, from the heat removal and corrosion protection points of view, the Ag-In-Cd alloy is needed to clad between Al alloys (Al5083). We attempted to obtain good bonding conditions for between Al5083 and ternary Ag-In-Cd alloys by HIPing tests. The good HIP condition was found for small test piece (20mm). Though a hardened layer due to the formation of AlAg was found in the bonding layer, the rupture strength of the bonding layer was more than 20 MPa, which was the calculated design stress. Bonding tests of a large size piece (20020030 mm), which simulated the real scale, were also performed according to the results of small size tests. The result also gave good bonding and enough required-mechanical-strength, however the rupture strength of the large size test was smaller than that of small one.

Design optimization of ADS plant proposed by JAERI

Saito, Shigeru; Tsujimoto, Kazufumi; Kikuchi, Kenji; Kurata, Yuji; Sasa, Toshinobu; Umeno, Makoto*; Nishihara, Kenji; Mizumoto, Motoharu; Ouchi, Nobuo; Takei, Hayanori; et al.

Nuclear Instruments and Methods in Physics Research A, 562(2), p.646 - 649, 2006/06

https://doi.org/10.1016/j.nima.2006.02.078

JAERI is conducting R&D on the Accelerator Driven System (ADS) to transmute minor actinides (MAs) contained in the high-level radioactive waste under the OMEGA (Options Making Extra Gains from Actinides and fission products) program. The present study discusses the design of the ADS plant and various R&D on the ADS. The reference design of ADS plant in JAERI is the 800 MWth, Pb-Bi eutectic (LBE) cooled, tank-type subcritical reactor loaded with (MA+Pu) nitride fuel. LBE is selected as a spallation target material. In our results of the optimization study on the neutronics of the ADS, we have adopted the maximum multiplication factor (k) of 0.97. From the results of the thermal-hydraulic analysis around the LBE spallation target, partition wall and flow control nozzle are required to keep the structural integrity around the core and the beam window. Feasibility of beam window was also discussed for transient conditions of proton beam.