Development of failure mitigation technologies for improving resilience of nuclear structures, 5; Resilience improvements of fast reactors by failure mitigation for beyond design high temperature accidents

Futagami, Satoshi; Ando, Masanori; Yamano, Hidemasa

Transactions of the 27th International Conference on Structural Mechanics in Reactor Technology (SMiRT 27) (Internet), 10 Pages, 2024/03

Investigation on natural circulation behavior for decay heat removal in reactor vessel of sodium-cooled fast reactor under severe accident condition, 1; Effect of decay-heat conditions on natural circulation behavior under dipped-type DHX operation conditions

Tsuji, Mitsuyo; Aizawa, Kosuke; Kobayashi, Jun; Kurihara, Akikazu

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 6 Pages, 2022/10

In sodium-cooled fast reactors (SFRs), decay heat removal after a core disruptive accident (CDA) is an important issue for the safety enhancement. Therefore, water experiments using a 1/10 scale experimental apparatus (PHEASANT) that simulates the reactor vessel of an SFR are conducted to investigate the natural circulation phenomena in the reactor vessel. In this study, experiments under the operation of the dipped-type DHX were conducted to investigate the effect of the heat generation ratio between the fuel debris on the core catcher in lower plenum and the reactor core remnant on the natural circulation behavior in the reactor vessel. The temperature distribution and the velocity distribution were measured under two heat generation conditions. Thus, the effect of the heat generation ratio between the fuel debris in the lower plenum and the reactor core remnant on the natural circulation behavior was quantitatively grasped under the dipped-type DHX operating conditions.

ASTRID nuclear island design; Advances in French-Japanese joint team development of decay heat removal systems

Hourcade, E.*; Curnier, F.*; Mihara, Takatsugu; Farges, B.*; Dirat, J.-F.*; Ide, Akihiro*

Proceedings of 2016 International Congress on Advances in Nuclear Power Plants (ICAPP 2016) (CD-ROM), p.1740 - 1745, 2016/04

In the framework of the French-Japanese agreement signed in 2014, CEA, AREVA NP, JAEA, and MHI/MFBR is jointly performing components design of ASTRID such as Decay Heat Removal Systems (DHRS). This paper is giving highlights of ASTRID DHRS current strategy. Focus is made on operating temperature diversification for in-vessel heat exchanger as well as core catcher coolability by an original features such as heat exchanger located within reactor cold pool, whose design was taken over by Japan team since 2014.

Comparisons of small ELM H-mode regimes on the Alcator C-Mod and JFT-2M tokamaks

Hubbard, A. E.*; Kamiya, Kensaku; Oyama, Naoyuki; Basse, N.*; Biewer, T.*; Edlund, E.*; Hughes, J. W.*; Lin, L.*; Porkolab, M.*; Rowan, W.*; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A121 - A129, 2006/05

https://doi.org/10.1088/0741-3335/48/5A/S11

Dedicated experiments were carried out to compare the properties, fluctuation behaviour and access conditions of these regimes. A common shape was developed which scaled the plasma boundary except for aspect ratio. Scans of density and input power were carried out at several values of q95, so as to achieve ranges of dimensionless parameters. A striking similarity of access conditions was seen. These results suggest common physical mechanisms for the H-mode regimes, which do not depend critically on aspect ratio over this range. On the other hand, several differences in the details of the edge fluctuations were found, and will be reported. The effect of wall conditioning via boronization on the H-mode regimes will also be discussed.

Pedestal characteristics in JFT-2M HRS H-mode plasma

Kamiya, Kensaku; Oyama, Naoyuki; Miura, Yukitoshi; Hubbard, A. E.*

Plasma Physics and Controlled Fusion, 46(11), p.1745 - 1755, 2004/11

https://doi.org/10.1088/0741-3335/46/11/005

Recent experiments in the JFT-2M tokamak have concentrated on the studies of the access condition for the H-mode operation without any large ELMs, namely High Recycling Steady (HRS) H-mode regime in terms of the pedestal parameters. The HRS regime is more likely at the higher edge density and lower edge temperature, while the ELMy H-mode having large ELMs appears at the lower edge density and higher edge temperature. It is found that the ELMy/HRS operational boundary occurs at the normalized electron collisionality of *1 in the plasma edge region, depending slightly on q. A key feature of the HRS H-mode is the presence of the coherent magnetic fluctuations in the frequency range of the order of 10-100 kHz. It is suggested that the edge MHD activities may keep an edge pressure below a certain level needed to induce a large ELM.

High-beta steady-state research and future directions on the Japan Atomic Energy Research Institute Tokamak-60 Upgrade and the Japan Atomic Energy Research Institute Fusion Torus-2 Modified

Ishida, Shinichi; JT-60 Team; JFT-2M Group

Physics of Plasmas, 11(5), p.2532 - 2542, 2004/05

https://doi.org/10.1063/1.1667487

no abstracts in English

Development of failure mitigation technologies for improving resilience of nuclear structures, 15; Conceptual study for improving resilience of next-generation nuclear power plants under extremely high temperature conditions

Futagami, Satoshi; Ando, Masanori; Yamano, Hidemasa; Kasahara, Naoto*

no journal, , 

To improve resilience of next-generation nuclear power plants, the authors have performed a structural analysis assuming a protected loss of heat sink event, which may cause all decay heat removal systems to lose their functions immediately after reactor shutdown. The results show how the reactor vessel and guard vessel deform under extremely high temperatures.