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Porcheron, E.*; Leblois, Y.*; Journeau, C.*; Delacroix, J.*; Molina, D.*; Suteau, C.*; Berlemont, R.*; Bouland, A.*; Lallot, Y.*; Roulet, D.*; et al.
Proceedings of International Topical Workshop on Fukushima Decommissioning Research (FDR2022) (Internet), 5 Pages, 2022/10
One of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. The URASOL project, which is undertaken by a French consortium consisting of ONET Technologies, CEA, and IRSN for JAEA/CLADS, is dedicated to acquiring basic scientific data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Heating process undertaken in the VITAE facility simulates some representative conditions of thermal cutting by LASER. For mechanical cutting, the core boring technique is implemented in the FUJISAN facility. Fuel debris simulants have been developed for inactive and active trials. The aerosols are characterized in terms of mass concentration, real time number concentration, mass size distribution, morphology, and chemical properties. The chemical characterization aims at identifying potential radioactive particles released and the associated size distribution, both of which are important information for assessing possible safety and radioprotection measures during the fuel debris retrieval operations at 1F.
Nakayoshi, Akira; Jegou, C.*; De Windt, L.*; Perrin, S.*; Washiya, Tadahiro
Nuclear Engineering and Design, 360, p.110522_1 - 110522_18, 2020/04
Times Cited Count：15 Percentile：82.17(Nuclear Science & Technology)Li, X.; Sato, Ikken; Yamaji, Akifumi*; Duan, G.*
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 8 Pages, 2018/07
Molten corium-concrete interaction (MCCI) is an important ex-vessel phenomenon that could happen during the late phase of a hypothetical severe accident in a light water reactor. In the present study, a three-dimensional (3-D) numerical study has been performed to simulate COMET-L3 test carried out by KIT with a stratified molten pool configuration of simulant materials with improved MPS method. The heat transfer between corium/crust/concrete was modeled with heat conduction between particles. Moreover, the potential influence of the siliceous aggregates was also investigated by setting up two different case studies since there was previous study indicating that siliceous aggregates in siliceous concrete might contribute to different axial and radial concrete ablation rates. The simulation results have indicated that metal melt as corium in MCCI can have completely different characteristics regarding concrete ablation pattern from that of oxidic corium, which needs to be taken into consideration when assessing the containment melt-through time in severe accident management.
Maruyama, Yu*; Moriyama, Kiyofumi; Nakamura, Hideo
Journal of Nuclear Science and Technology, 39(8), p.854 - 864, 2002/08
Times Cited Count：4 Percentile：28.64(Nuclear Science & Technology)no abstracts in English
Moriyama, Kiyofumi; Nakamura, Hideo; Hirano, Masashi
Nihon Kikai Gakkai Dai-8-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, p.209 - 214, 2002/06
Through a review of experimental works on steam explosions and consideration on the uncertainty in the methodology for plant scale analysis of each stage of the phenomena, it was identified that the molten jet breakup process in premixing has an important uncertainty caused by lack of experimental knowledge. Based on this perspective, an experimental work are under planning at Japan Atomic Energy Research Institute (JAERI), in which the premixing stage of steam explosions in a deep water pool is modeled by high temperature oxide melts. Melt material and scale of the experiment were examined in terms of the simulation capability of the jet breakup mechanism in a plant scale phenomena. Materials and geometrical scale considered adequate were found.
as simulated corium debrisMorimoto, Kyoichi; Hirooka, Shun; Akashi, Masatoshi; Watanabe, Masashi
no journal, ,
The influence of Gd on characteristics of debris is important for removing the debris from the reactors of Fukushima Daiichi Nuclear Power Plant because subassemblies of nuclear fuels containing Gd
O
were loaded in the some reactor cores. Additionally, it is important to assess the distribution state of Gd from the anxiety of re-criticality caused by the relocation of debris while removing them. In this study, sintered pellets of (U
Gd
Zr
)O (y=0,0.5, 2-x=1.989-2.000) were melted and solidified to prepare specimens of simulated corium debris. Phase states and fundamental properties of them were evaluated.
Sudo, Ayako
no journal, ,
In order to obtain the knowledge on the re-distribution of various elements under the solidification process of molten corium, the fundamental experiment on the U-Zr-Gd-O melt was performed. As the core-melt constituents, a powder mixture of wt.70%UO+30%ZrO with adding of wt.2%GdO was prepared with mass of 655.5g. These powders were melted in a cold crucible using induction heating technique in the air atmosphere with metallic zirconium (6g) as an initiator. For the corium microstructure study, sample pieces from solidified ingot were subjected to phase identification and elemental analysis by XRD and SEM/EDX. For the evaluation of the characteristics of corium debris under the various solidification processes, two heating tests with different cooling rates were performed. During quick-solidification test (J1) ingot of 4.8cm was obtained. The near-bottom region of J1 sample was crystallized and not melted. The structure of slow-solidification sample (J2) was similar to J1, however, it was formed big cavity under the upper crust of ingot. This cavity was formed during slow-solidification process due to volume shrinkage. Both of samples were found that Gd was concentrated in the inner region where the later crystallization of the melt was occurred.
Kitagaki, Toru; Yano, Kimihiko; Washiya, Tadahiro; Haquet, J.-F.*; Boulin, A.*; Piluso, P.*
no journal, ,
Yano, Kimihiko; Kitagaki, Toru; Ogino, Hideki; Washiya, Tadahiro; Pascal, P.*; Jean-Fran
ois, H.*; Patricia, C.*; Anne, B.*; Brissonneau, L.*; Brigitte, T.*; et al.
no journal, ,
In a collaborative agreement with Commissariat 
l'
nergie atomique et aux nergies alternatives (CEA), the characterization of MCCI products was carried out using the materials that CEA produced in its past large-scale MCCI test. Samples of a corium oxide phase and an interface of corium/concrete phases were selected. They were observed by SEM/EDS and measured by Vickers Hardness Tester.
Akashi, Masatoshi; Morimoto, Kyoichi
no journal, ,
