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Wada, Yuki*; Matsumoto, Takahiro*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Furuta, Yoshihiro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Okada, Go*; Nanto, Hidehito*; et al.
Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12
Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*
Annals of Nuclear Energy, 162, p.108512_1 - 108512_10, 2021/11
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)The objectives of this study are as follows: to understand the characteristics, degree of passive safety features for heat removal were compared for RCCSs based on atmospheric radiation and based on atmospheric natural circulation under the same conditions. Next, simulations on accidental conditions, such as increasing average heat-transfer coefficient via natural convection due to natural disasters, were performed with STAR-CCM+, and methodology to control the amount of heat removal was discussed. As a result, a new RCCS based on atmospheric radiation is recommended because of the excellent degree of passive safety features/conditions, and the amount of heat removal by heat transfer surfaces which can be controlled. Finally, methodology to determine structural thickness of scaled-down heat removal test facilities for reproducing natural convection and radiation was developed, and experimental methods by using pressurized and decompressed chambers was also proposed.
Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*
Annals of Nuclear Energy, 151, p.107867_1 - 107867_11, 2021/02
Times Cited Count：1 Percentile：16.35(Nuclear Science & Technology)A new RCCS with passive safety features consists of two continuous closed regions. One is a region surrounding RPV. The other is a cooling region with heat transferred to the ambient air. The new RCCS needs no electrical or mechanical driving devices. We compared the RCCS using atmospheric radiation with that using atmospheric natural circulation in terms of passive safety features and control methods for heat removal. The magnitude relationship for passive safety features is heat conduction 
radiation natural convection. Therefore, the magnitude for passive safety features of the former RCCS can be higher than that of the latter RCCS. In controlling the heat removal, the former RCCS changes the heat transfer area only. On the other hand, the latter RCCS needs to change the chimney effect. It is necessary to change the air resistance in the duct. Therefore, the former RCCS can control the heat removal more easily than the latter RCCS.
Sheikh, M. A. R.*; Liu, X.*; Matsumoto, Tatsuya*; Morita, Koji*; Guo, L.*; Suzuki, Toru*; Kamiyama, Kenji
Energies (Internet), 13(19), p.5018_1 - 5018_15, 2020/10
Times Cited Count：7 Percentile：22.89(Energy & Fuels)Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*
Annals of Nuclear Energy, 133, p.830 - 836, 2019/11
Times Cited Count：2 Percentile：21.58(Nuclear Science & Technology)A RCCS having passive safety features through radiation and natural convection was proposed. The RCCS design consists of two continuous closed regions: an ex-reactor pressure vessel region and a cooling region with a heat-transfer surface to ambient air. The RCCS uses a novel shape to remove efficiently the heat released from the RPV through as much radiation as possible. Employing air as the working fluid and ambient air as the ultimate heat sink, the RCCS design can strongly reduce the possibility of losing the working fluid and the heat sink for decay-heat-removal. Moreover, the authors started experiment research with using a scaled-down heat-removal test facility. Therefore, this study propose a comparative methodology between an actual RCCS and a scaled-down heat-removal test facility.
Wada, Yuki*; Enoto, Teruaki*; Nakamura, Yoshitaka*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakazawa, Kazuhiro*; Morimoto, Takeshi*; Sato, Mitsuteru*; Matsumoto, Takahiro*; Yonetoku, Daisuke*; et al.
Communications Physics (Internet), 2(1), p.67_1 - 67_9, 2019/06
Times Cited Count：49 Percentile：93.08(Physics, Multidisciplinary)Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*
Annals of Nuclear Energy, 122, p.201 - 206, 2018/12
Times Cited Count：3 Percentile：30.05(Nuclear Science & Technology)A RCCS having passive safety features through radiation and natural convection was proposed. The RCCS design consists of two continuous closed regions: an ex-reactor pressure vessel region and a cooling region with a heat-transfer surface to ambient air. The RCCS uses a novel shape to remove efficiently the heat released from the RPV through as much radiation as possible. Employing air as the working fluid and ambient air as the ultimate heat sink, the RCCS design can strongly reduce the possibility of losing the working fluid and the heat sink for decay-heat-removal. This study addresses an improvement of heat-removal capability using heat conduction on the RCCS. As a result, a heat flux removed by the RCCS could be doubled; therefore, it is possible to halve the height of the RCCS or increase the thermal reactor power.
Hosomi, Seisuke*; Akashi, Tomoyasu*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Takamatsu, Kuniyoshi
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 7 Pages, 2018/11
A new RCCS with passive safety features consists of two continuous closed regions. One is a region surrounding RPV. The other is a cooling region with heat transferred to the ambient air. The new RCCS needs no electrical or mechanical driving devices. We started experiment research with using a scaled-down test section. Three experimental cases under different emissivity conditions were performed. We used Monte Carlo method to evaluate the contribution of radiation to the total heat released from the heater. As a result, after the heater wall was painted black, the contribution of radiation to the total heat could be increased to about 60%. A high emissivity of RPV surface is very effective to remove more heat from the reactor. A high emissivity of the cooling part wall is also effective because it not only increases the radiation emitted to the ambient air, but also may increase the temperature difference among the walls and enhance the convection heat transfer in the RCCS.
Kato, Masatsugu*; Funakoshi, Kanji*; Liu, X.*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Kamiyama, Kenji
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-11) (Internet), 7 Pages, 2018/11
Sheikh, Md. A. R.*; Son, E.*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Matsuba, Kenichi; Kamiyama, Kenji; Suzuki, Toru*
Journal of Nuclear Science and Technology, 55(6), p.623 - 633, 2018/06
Times Cited Count：14 Percentile：79.66(Nuclear Science & Technology)During core-disruptive accidents in sodium-cooled fast reactors, the sedimentation behavior of fragmented debris is crucial for in-vessel retention. The height of the beds formed may influence both the cooling of the bed and the neutronic characteristics. To develop an experimental database of bed formation behavior, a series of experiments using simulant materials, namely, Al
O
, ZrO, and stainless steel, were performed under gravity-driven discharge of solid particles from a nozzle into a quiescent cylindrical water pool. The bed height was measured for particles of different size, density, and sphericity, and an injection nozzle with varying diameter, injection velocity, and injection height. From these experiments, an empirical correlation was established to predict the bed height for both homogeneous and mixed particles for the different properties. This correlation reproduces reasonably well the experimental trend in bed height.
Shamsuzzaman, M.*; Horie, Tatsuro*; Fuke, Fusata*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Tagami, Hirotaka; Suzuki, Toru*; Tobita, Yoshiharu
Annals of Nuclear Energy, 111, p.474 - 486, 2018/01
Times Cited Count：17 Percentile：85.18(Nuclear Science & Technology)Kawata, Ryo*; Ohara, Yohei*; Sheikh, Md. A. R.*; Liu, X.*; Matsumoto, Tatsuya*; Morita, Koji*; Guo, L.*; Kamiyama, Kenji; Suzuki, Toru
Proceedings of 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17) (USB Flash Drive), 14 Pages, 2017/09
Sheikh, M. A. R.*; Son, E.*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Matsuba, Kenichi; Kamiyama, Kenji; Suzuki, Toru
Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 10 Pages, 2016/11
During the material relocation phase of core disruptive accidents in sodium-cooled fast reactors, the sedimentation behavior of fragmented debris leading to the formation of debris beds is crucial for in-vessel retention by debris bed cooling. In this study, a series of experiments using simulant materials was performed to develop an experimental database of bed formation behavior by gravity driven discharge of solid particles from a nozzle into a quiescent cylindrical water pool. The bed height as well as the bed shape was measured. Three types of spherical and non-spherical particles, namely AlO, ZrO and stainless steel with different size were employed to study the effect of key experimental parameter on debris bed mound shape. Based on the experimental results, an empirical correlation as experimental database was proposed to predict the particle bed height. The proposed correlation reasonably reproduces the experimental trend of the bed height variation on the crucial factors. This result demonstrates a wide applicability of the proposed empirical model to predict the bed height in terms of all crucial factors with reasonable accuracy.
Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Morita, Koji*
Annals of Nuclear Energy, 96, p.137 - 147, 2016/10
Times Cited Count：5 Percentile：43.41(Nuclear Science & Technology)After Fukushima Daiichi nuclear disaster by TEPCO, a cooling system to prevent core damage became more important from the perspective of defense in depth. Therefore, a new, highly efficient RCCS with passive safety features without a requirement for electricity and mechanical drive is proposed. Employing the air as the working fluid and the ambient air as the ultimate heat sink, the new RCCS design strongly reduces the possibility of losing the heat sink for decay heat removal. The RCCS can always stably and passively remove a part of the released heat at the rated operation and the decay heat after reactor shutdown. Specifically, emergency power generators are not necessary and the decay heat can be passively removed for a long time, even forever if the heat removal capacity of the RCCS is sufficient. We can also define the experimental conditions on radiation and natural convection for the scale-down heat removal test facility.
Sheikh, M. A. R.*; Son, E.*; Kamiyama, Motoki*; Morioka, Toru*; Matsumoto, Tatsuya*; Morita, Koji*; Matsuba, Kenichi; Kamiyama, Kenji; Suzuki, Toru
Proceedings of 11th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-11) (USB Flash Drive), 12 Pages, 2016/10
This paper reports an experimental evaluation on debris bed formation characteristics in core-disruptive accidents cogitating the heterogeneous mixture of particles. In the present study, to appraise the characteristics, a series of experiments was accomplished by gravity driven discharge of solid binary mixtures of particles as simulant debris from a nozzle into a quiescent water pool in isothermal condition at room temperature. Currently, two types of spherical particles, namely Alumina and stainless steel with different diameter are employed to study the effect of key experimental parameters on bed mound shape. In experimental investigation both convex and concave mound shapes were perceived based on the effect of particle size and nozzle diameter. The present outcomes could be useful to validate numerical models and simulation codes of particulate debris sedimentation.
Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Morita, Koji*
Proceedings of 2016 International Congress on Advances in Nuclear Power Plants (ICAPP 2016) (CD-ROM), p.1250 - 1257, 2016/04
After Fukushima Daiichi nuclear disaster by TEPCO, a cooling system to prevent core damage became more important from the perspective of defense in depth. Therefore, a new, highly efficient RCCS with passive safety features without a requirement for electricity and mechanical drive is proposed. Employing the air as the working fluid and the ambient air as the ultimate heat sink, the new RCCS design strongly reduces the possibility of losing the heat sink for decay heat removal. The RCCS can always stably and passively remove a part of the released heat at the rated operation and the decay heat after reactor shutdown. Specifically, emergency power generators are not necessary and the decay heat can be passively removed for a long time, even forever if the heat removal capacity of the RCCS is sufficient. We can also define the experimental conditions on radiation and natural convection for the scale-down heat removal test facility.
Cheng, S.; Tagami, Hirotaka; Yamano, Hidemasa; Suzuki, Toru; Tobita, Yoshiharu; Takeda, Shohei*; Nishi, Shimpei*; Nishikido, Tatsuya*; Zhang, B.*; Matsumoto, Tatsuya*; et al.
Journal of Nuclear Science and Technology, 51(9), p.1096 - 1106, 2014/09
Times Cited Count：25 Percentile：87.38(Nuclear Science & Technology)Cheng, S.; Tagami, Hirotaka; Yamano, Hidemasa; Suzuki, Toru; Tobita, Yoshiharu; Nakamura, Yuya*; Takeda, Shohei*; Nishi, Shimpei*; Zhang, B.*; Matsumoto, Tatsuya*; et al.
Mechanical Engineering Journal (Internet), 1(4), p.TEP0022_1 - TEP0022_16, 2014/08
Cheng, S.; Tagami, Hirotaka; Yamano, Hidemasa; Suzuki, Toru; Tobita, Yoshiharu; Zhang, B.*; Matsumoto, Tatsuya*; Morita, Koji*
Annals of Nuclear Energy, 63, p.188 - 198, 2014/01
Times Cited Count：33 Percentile：92.29(Nuclear Science & Technology)Cheng, S.; Tagami, Hirotaka; Yamano, Hidemasa; Suzuki, Toru; Tobita, Yoshiharu; Nakamura, Yuya*; Zhang, B.*; Matsumoto, Tatsuya*; Morita, Koji*
Proceedings of International Conference on Power Engineering 2013 (ICOPE 2013) (USB Flash Drive), 6 Pages, 2013/10
