Hong, Z.*; Pellegrini, M.*; Erkan, N.*; Liao, H.*; Yang, H.*; Yamano, Hidemasa; Okamoto, Koji*
Annals of Nuclear Energy, 180, p.109462_1 - 109462_9, 2023/01
A series of experiments were conducted using BC material and SUS304 tubes as a simulant of the real control rods. Reaction rate constant data in the 1450K-1500K range were obtained, and are consistent with the reference values. The reaction layer microstructure observation and the associated chemical composition analysis were also carried onto the experiment samples.
Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Fukuyama, Hiroyuki*; Higashi, Hideo*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Morita, Koji*; Nakamura, Kinya*; Fukai, Hirofumi*; et al.
Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-13) (Internet), 12 Pages, 2022/09
This paper describes the project overview and progress of experimental and analytical studies conducted until 2020. Specific results in this paper are the measurement of the eutectic reaction rates and the validation of physical model describing the eutectic reaction in the analysis code through the numerical analysis of the BC-SS eutectic reaction rate experiments in which a BC pellet was placed in a SS crucible.
Li, C.; Uchibori, Akihiro; Takata, Takashi; Pellegrini, M.*; Erkan, N.*; Okamoto, Koji*
Dai-25-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2021/07
The capability of stable cooling and avoiding re-criticality on the debris bed are the main issues for achieving IVR (In-Vessel Retention). In the actual situation, the debris bed is composed of mixed-density debris particles. Hence, when these mixed-density debris particles were launched to re-distribute, the debris bed would possibly form a density-stratified distribution. For the proper evaluation of this scenario, the multi-physics model of CFD-DEM-Monte-Carlo based neutronics is established to investigate the coolability and re-criticality on the heterogeneous density-stratified debris bed with considering the particle relocation. The CFD-DEM model has been verified by utilizing water injection experiments on the mixed-density particle bed in the first portion of this research. In the second portion, the coupled system of the CFD-DEM-Monte-Carlo based neutronics model is applied to reactor cases. Afterward, the debris particles' movement, debris particles' and coolant's temperature, and the k-eff eigenvalue are successfully tracked. Ultimately, the relocation and stratification effects on debris bed's coolability and re-criticality had been quantitatively confirmed.
Rizaal, M.; Saito, Takumi*; Okamoto, Koji*; Erkan, N.*; Nakajima, Kunihisa; Osaka, Masahiko
Mechanical Engineering Journal (Internet), 7(3), p.19-00563_1 - 19-00563_10, 2020/06
The adsorption of cesium (Cs) on calcium silicate insulation of primary piping system is postulated to contribute in high dose rate of surrounding pedestal area in Fukushima Daiichi NPP unit 2. In this study, room-temperature experiment of Cs adsorption on calcium silicate has been studied as an initial approach of Cs adsorption behavior toward higher temperature condition. As the result of analyzing of Cs adsorption kinetics, it was expected that the underlying adsorption mechanism is chemisorption. Furthermore, analysis of adsorption isotherm suggested unrestricted monolayer formation followed by multilayer formation.
Chai, P.; Kondo, Masahiro*; Erkan, N.*; Okamoto, Koji*
Annals of Nuclear Energy, 103, p.227 - 237, 2017/05
A two-dimensional computational code was developed using multi-physics models to simulate MCCI phenomena based on the moving particle semi-implicit (MPS) method. In contrast to previous studies, gas generation was simulated by calculating the force balance of the bubbles in the liquid pool in order to investigate its influence on the ablation behavior. Moreover, chemical reaction was modeled by calculating the heat release from the redox reaction between the corium and melted concrete during the erosion process. CCI-2 and CCI-3 tests were simulated by applying this code to study the aspects that may affect the ablation profile with different concrete types. The simulation result generally matches the experimental results on both axial and radial ablation rates. Application of the gas release and chemical reaction model suggested that one possible reason for the anisotropic ablation profile observed in the siliceous concrete tests is the heat transfer enhancement near the sidewall from the gas release and chemical reaction. In contrast, the test using limestone-rich concrete generated an isotropic ablation profile because axial ablation was also enhanced by the large gas discharge from the bottom concrete. In addition to the ablation profile, the crust formation and concrete-corium interface profile at the bottom in the CCI-3 test were reproduced with the help of the proposed models.
Rizaal, M.; Nakajima, Kunihisa; Osaka, Masahiko; Saito, Takumi*; Erkan, N.*; Okamoto, Koji*
no journal, ,
Experimental study using thermogravimetry and X-ray diffractometry was conducted to investigate chemical interaction between calcium silicate insulation and cesium hydroxide under steam and hydrogen atmospheres. This interaction might be one of the causes for the high dose rate reading outside the pedestal in 1F, Unit2. Our results suggested that some chemical interaction occurred in temperature range of 575-730C regardless of atmospheres.
Yamano, Hidemasa; Takai, Toshihide; Emura, Yuki; Higashi, Hideo*; Fukuyama, Hiroyuki*; Nishi, Tsuyoshi*; Ota, Hiromichi*; Morita, Koji*; Nakamura, Kinya*; Fukai, Hirofumi*; et al.
no journal, ,
A research project has been conducting thermophysical property measurement of a eutectic melt, eutectic melting experiments and material analysis, physical model development for the eutectic melting reaction, and reactor application analysis in order to simulate the eutectic melting reaction and relocation behavior of boron carbide as a control rod material and stainless steel during a core disruptive accident in an advanced sodium-cooled fast reactor designed in Japan. This paper describes the project overview and progress until JFY2020.