Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Takamatsu, Kuniyoshi
Kakushinteki Reikyaku Gijutsu; Mekanizumu Kara Soshi, Shisutemu Kaihatsu Made, p.179 - 183, 2024/01
The HTGR has excellent safety, and even in the event of an accident where the reactor coolant is lost, the decay heat and residual heat in the core can be dissipated from the outer surface of the RPV, so the fuel temperature never exceeds the limit value, and the core stabilizes. On the other hand, regarding the cooling system that transports the heat emitted from the RPV to the final heat sink, an active cooling system using forced circulation of water by a pump, etc., and a passive cooling system using natural circulation of the atmosphere have been proposed. However, there is a problem that the cooling performance is affected by the operation of dynamic equipment and weather conditions. This paper presents an overview of a new cooling system concept using radiative cooling, which has been proposed to solve the above problem, and introduces the results of analysis and experiments aimed at confirming the feasibility of this concept.
Banno, Masaki*; Funatani, Shumpei*; Takamatsu, Kuniyoshi
Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 7 Pages, 2023/05
A fundamental study on the safety of a passive cooling system for the RPV with radiative cooling is conducted. The object of this study is to demonstrate that passive RPV cooling system with radiative cooling is extremely safe and reliable even in the event of natural disasters. Therefore, an experimental apparatus, which is about 1/20 scale of the actual cooling system, was fabricated with several stainless steel containers. The surface of the heating element in the experimental apparatus simulates the surface of the RPV, and the heating element generates natural convection and radiation. A comparison of the Grashof number between the actual cooling system and the experimental apparatus confirmed that both were turbulent, and the experimental results as a scale model are valuable. Moreover, the experimental results confirmed that the heat generated from the surface of the RPV during the rated operation can be removed.
Takamatsu, Kuniyoshi; Funatani, Shumpei*
Proceedings of 2023 International Congress on Advanced in Nuclear Power Plants (ICAPP 2023) (Internet), 17 Pages, 2023/04
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. Therefore, the authors concluded that the proposed RCCS based on atmospheric radiation has the advantage that the temperature of the RPV can be stably maintained against disturbances in the outside air (ambient air). Moreover, methodology to utilize all the heat emitted from the RPV surface for increasing the degree of waste-heat utilization was discussed.
Banno, Masaki*; Funatani, Shumpei*; Takamatsu, Kuniyoshi
Yamanashi Koenkai 2022 Koen Rombunshu (CD-ROM), 6 Pages, 2022/10
A fundamental study on the safety of a passive cooling system for the reactor pressure vessel (RPV) with radiative cooling is conducted. The object of this study is to demonstrate that passive RPV cooling system with radiative cooling is extremely safe and reliable even in the event of natural disasters. Therefore, an experimental apparatus, which is about 1/20 scale of the actual cooling system, was fabricated with several stainless steel containers. The surface of the heating element in the experimental apparatus simulates the surface of the RPV, and the heating element generates natural convection and radiation. As a result of the experiments, we succeeded in visualizing the natural convection in the experimental apparatus in detail.
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.
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.
Ota, Hirokazu*; Ohgama, Kazuya; Yamano, Hidemasa
Proceedings of International Nuclear Fuel Cycle Conference / Light Water Reactor Fuel Performance Conference (Global/Top Fuel 2019) (USB Flash Drive), p.30 - 39, 2019/09
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.
Takamatsu, Kuniyoshi; Hu, R.*
Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 12 Pages, 2014/12
continuous closed regions; one is an ex-reactor pressure vessel (RPV) region and another is a cooling region having heat transfer area to ambient air assumed at 40 (
C). The RCCS uses novel shape so that the heat released from the RPV can be removed efficiently with radiation and natural convection. Employing the air as the working fluid and the ambient air as the ultimate heat sink, the new RCCS design greatly reduces the possibility of losing the heat sink for decay heat removal. Therefore, HTGRs and VHTRs adopting the new RCCS design can avoid core melting owing to overheating the fuels.
JAERI-Tech 97-045, 601 Pages, 1997/10
no abstracts in English
Honda, Takuro*; *; *; *; Seki, Yasushi; Aoki, Isao; Kunugi, Tomoaki
Journal of Nuclear Science and Technology, 32(4), p.265 - 274, 1995/04
Times Cited Count：8 Percentile：63.11(Nuclear Science & Technology)no abstracts in English
Murao, Yoshio
Genshiryoku Kogyo, 41(1), p.31 - 35, 1995/00
no abstracts in English
Asahi, Yoshiro; ; *
Nuclear Science and Engineering, 96, p.73 - 84, 1987/00
Times Cited Count：3 Percentile：51.95(Nuclear Science & Technology)no abstracts in English
Takamatsu, Kuniyoshi; Matsumoto, Tatsuya*; Morita, Koji*
no journal, ,
After the accident at the Fukushima NPPs, measures to prevent core damage in terms of defense in depth had become more and more important. Researches regarding cooling system having novel safety features are crucially essential subjects. Therefore, a new Reactor Cavity Cooling System (RCCS) having passive safety features is proposed. The RCCS does not require active cooling systems and never lost heat sink in the same way as the accident at the Fukushima NPPs. The RCCS can become a base load cooling system like a base load power station and remove a part of emissive heat in rated operation and a part of decay heat after reactor shutdown, constantly, stably and passively.
Ota, Hirokazu*; Ohgama, Kazuya; Yamano, Hidemasa
no journal, ,
no abstracts in English
Akashi, Tomoyasu*; Hosomi, Seisuke*; Ifuku, Hiroki*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Takamatsu, Kuniyoshi
no journal, ,
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.
Nishimori, Yuya*; Akashi, Tomoyasu*; Uwada, Shogo*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Takamatsu, Kuniyoshi
no journal, ,
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 for understanding effect of expansion of heat transfer areas of the cooling region on cooling performance and heat transfer characteristics. For example, two experiments with and without insulation covering a part of the heat transfer area of the cooling region were performed. As a result, in the case of the experiment without the insulation, the heater power could be increased; therefore, it is effective for an actual RCCS to increase heat transfer areas.
Kusumi, Koji*; Ota, Hirokazu*; Ohgama, Kazuya; Yamano, Hidemasa; Futagami, Satoshi
no journal, ,
no abstracts in English
