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Nakamura, Hironori*; Hayakawa, Satoshi*; Shibata, Akihiro*; Sasa, Kyohei*; Yamano, Hidemasa; Kubo, Shigenobu
Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 7 Pages, 2022/10
In order to evaluate long-term coolablity of the debris-bed with decay heat, a three-dimensional calculation method coupled with the debris bed module was developed in this study. The coupled code calculation results show that natural circulation of the coolant between the hot pool and the cold pool is established through the four intermediate heat exchangers after the activation of the dipped direct heat exchangers. The cold pool with the debris-bed is continually cooled not only by the natural circulation flow, but also by heat transfer to the hot pool through the plenum separation plate between the hot pool and the cold pool. The effect of the three-dimensional flow field around the core catcher on the temperature in the debris-bed is about 20K under the current calculation condition.
Yamano, Hidemasa; Kubo, Shigenobu; Sasa, Kyohei*; Shibata, Akihiro*; Hourcade, E.*; Dirat, J. F.*
Proceedings of 29th International Conference on Nuclear Engineering (ICONE 29) (Internet), 9 Pages, 2022/08
This paper describes coolability evaluations of a debris bed with a variety of decay heat removal system (DHRS) operating conditions with a whole vessel model assuming fuel accumulation on the core catcher in a short term. The evaluation tool is a one-dimensional plant dynamics code, Super-COPD, with a debris bed module. The coolability evaluations have indicated that the current core catcher design secures sufficient natural circulation flows around the core catcher to ensure the debris bed cooling when at least one circuit of DHRS was activated. Sensitivity analyses under a pessimistic condition have shown that the debris bed is coolable with at least one circuit of improved DHRS even if most of fuel accumulates on the core catcher in a short term.
Matsuo, Eiji*; Sasa, Kyohei*; Koyama, Kazuya*; Yamano, Hidemasa; Kubo, Shigenobu; Hourcade, E.*; Bertrand, F.*; Marie, N.*; Bachrata, A.*; Dirat, J. F.*
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 5 Pages, 2019/05
Discharged molten-fuel from the core during Core Disruptive Accident (CDA) could become solidified particle debris by fuel-coolant interaction in the lower sodium plenum, and then the debris could form a bed on a core catcher located at the bottom of the reactor vessel. Coolability evaluations for the debris bed are necessary for the design of the core catcher. The purpose of this study is to evaluate the coolability of the debris bed on the core catcher for the ASTRID design. For this purpose, as a first step, the coolability calculations of the debris beds formed both in short term and later phase have been performed by modeling only the debris bed itself. Thus, details of core catcher design and decay heat removal system are not described in this paper. In all the calculations, coolant temperature around the debris bed is a parameter. The calculation tool is the debris bed module implemented into a one-dimensional plant dynamics code, Super-COPD. The evaluations have shown that the debris beds formed both in short term and later phase are coolable by the design which secures sufficient coolant flow around the core catcher located in the cold pool.
Nishimura, Satoshi*; Satake, Masaaki*; Nishi, Yoshihisa*; Nemoto, Yoshiyuki; Kaji, Yoshiyuki
Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 8 Pages, 2019/05
In this study, accident progression analyses in the SFP were performed to investigate cooling effects of the SFP spray and an alternate water injection in the loss-of-pool water accident with MAAP ver. 5.05 beta. Fuel cladding oxidation model which was created by JAEA based on their experimental data was selected and applied in the present calculations. In case of an assessment of SFP spray effects, decay heat, spray fraction going into the fuel assembly, spray droplet diameter, spray start time were selected as analytical parameters. When the SFP spray of 12.5 kg/s (200 GPM) starts 4 hours after the onset of the accident against the spent fuels with 4 months cooling and if the spray fraction going into the fuel assembly is greater than 30%, the maximum cladding temperature can be maintained under 727
C (1000 K), resulting in avoiding the cladding failure.
Matsumoto, Toshinori; Kawabe, Ryuhei; Sugiyama, Tomoyuki; Maruyama, Yu
Proceedings of 10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-10) (USB Flash Drive), 9 Pages, 2016/11
During severe accident at nuclear power stations, molten core material jet could be discharged from the reactor pressure vessel into the water pool formed at the pedestal or cavity in the containment vessel. To improve the JASMINE code, The method for determining particle diameters which follow the Rosin-Rammler distribution was implemented. The jet breakup experiments, DEFOR-A conducted by KTH (Royal Institute of Technology, Sweden) were analyzed with the code. The influence of the experimental conditions, such as water subcooling, melt jet diameter and superheat were discussed. A crust layer formation model was also implemented in the code. The analyses using the model were carried out for the melt spreading experiments, PULiMS conducted by KTH. The spreading area was overestimated. Further improvement of the melt spreading model were discussed to close the gaps by introducing additional models such as heat conduction in the substrate materials, void formed inside the melt and so on.
Sugiyama, Tomoyuki; Fuketa, Toyoshi
IAEA-TECDOC-1320, p.102 - 110, 2002/11
This report discusses effect of cladding surface pre-oxidation on fuel rod coolability during reactivity initiated accident (RIA) conditions. NSRR irradiated fuel experiments had shown cladding surface temperature lower than fresh fuel experiments. One possible speculation for the temperature difference is that oxide layer at the cladding outer surface enhanced heat transfer. To verify the speculation, pulse irradiation tests were performed on fuel rods with three different surface conditions: without oxide layer, with 1
m-thick and 10m-thick oxide layer. Transient records of the cladding surface temperature showed the critical heat flux and the minimum heat flux increased for the oxidized fuel rods. These effects depend on presence of the oxide layer, not on the thickness of the layer, because no difference existed between results from 1m and 10m rods.
Hidaka, Akihide; Maruyama, Yu; Ueno, Shingo*; Sugimoto, Jun
JAERI-Conf 99-005, p.49 - 55, 1999/07
no abstracts in English
Yamano, N.; Maruyama, Yu; Moriyama, Kiyofumi; Sugimoto, Jun
NEA/CSNI/R(96)24, 0, p.1 - 49, 1996/00
no abstracts in English
Yamano, N.; Maruyama, Yu; Moriyama, Kiyofumi; Kudo, Tamotsu; H.S.Park*; Sugimoto, Jun
Proc. of 11th KAIF/KNS Annual Conf., 0, p.827 - 838, 1996/00
no abstracts in English
Sugimoto, Jun; Hashimoto, Kazuichiro; Yamano, N.; Maruyama, Yu
Nihon Genshiryoku Gakkai "Genshiro Kakuno Yoki Shinraisei Jissho Shiken Ni Kansuru Chosa Hokokusho, Heisei-5-Nendo", 0, p.3 - 192, 1994/00
no abstracts in English
Yamano, N.; Sugimoto, Jun; Maruyama, Yu; Soda, Kunihisa
NUREG/CP-0127, 0, p.271 - 281, 1993/00
no abstracts in English
Maruyama, Yu; Abe, Yutaka; *; Soda, Kunihisa
JAERI-M 89-054, 142 Pages, 1989/05
no abstracts in English
Abe, Yutaka; Maruyama, Yu; *; Soda, Kunihisa
JAERI-M 89-048, 58 Pages, 1989/05
no abstracts in English
Matsumoto, Toshinori; Kawabe, Ryuhei; Sugiyama, Tomoyuki; Maruyama, Yu
no journal, ,
no abstracts in English
Kawabe, Ryuhei; Matsumoto, Toshinori; Sugiyama, Tomoyuki; Maruyama, Yu
no journal, ,
no abstracts in English
Kawabe, Ryuhei; Matsumoto, Toshinori; Ajima, Kohei; Sugiyama, Tomoyuki; Maruyama, Yu
no journal, ,
no abstracts in English
Kido, Kentaro
no journal, ,
no abstracts in English
Kikuchi, Wataru*; Akiba, Miyuki*; Hotta, Akitoshi*; Alexander, K.*; Walter, V.*; Sevostian, B.*; Matsumoto, Toshinori
no journal, ,
To develop the analytical models for jet breakup and debris bed formation, we are conducting experiments that simulate these behaviors. Various uncertainty items associate to the experiment were clarified, and the reflection in the analysis model was examined.
Nakamura, Hironori*; Shibata, Akihiro*; Hayakawa, Satoshi*; Yamano, Hidemasa; Kubo, Shigenobu
no journal, ,
The coolablity of the debris-bed on a core catcher was evaluated using a three-dimensional CFD code coupled with the debris bed module in this study. The coupled code calculation results showed the prospect to attain a long-term stable cooling.
