TY - JOUR
T1 - 2D MPS method analysis of ECOKATS-V1 spreading with crust fracture model
AU - Jubaidah,
AU - Umazume, Yuki
AU - Takahashi, Nozomu
AU - Li, Xin
AU - Duan, Guangtao
AU - Yamaji, Akifumi
N1 - Funding Information:
The authors gratefully acknowledge that this work was financially support by Indonesia Endowment Fund for Education (LPDP) [grant number: PRJ-6901/LPDP.3/2016]. This work also supported by the Physics Department of the State University of Medan and Directorate General of Higher Education, Ministry of Education, Culture, Research, and Technology Republic of Indonesia. A part of this study is the result of “Estimation of the In-Depth Debris Status of Fukushima Unit-2 and Unit-3 with Multi-Physics Modeling”, carried out under Nuclear Energy Science & Technology and Human Resource Development Project (through concentrating wisdom). A part of this study is the result of “Understanding Mechanisms of Severe Accidents and Improving Safety of Nuclear Reactors by Computer Science” of Waseda Research Institute for Science and Engineering and the authors acknowledge support of the Institute for Advanced Theoretical and Experimental Physics, Waseda University.
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2021/8/1
Y1 - 2021/8/1
N2 - Understanding the ex-vessel spreading behavior of molten core materials (corium) on the reactor containment floor is of great importance for designing, managing, and evaluating severe accidents of light water reactors. Among some simulated ex-vessel corium spreading experiments, temporal termination and restart of the flow (stop-and-go) were highlighted in the ECOKATS-V1 experiment, in which the simulant oxide melt (consisted of 41% of Al2O3, 24% of SiO2, 19% of CaO, and 16% of FeO) was released into a 1-D channel, and the spreading behavior seemed to have temporarily stopped and restarted following crust formation and breach at the spreading leading edge. The preceding study developed crust formation and breach models for the Lagrangian-based Moving Particle Semi-Implicit (MPS) method to analyze such spreading. However, the applicability of the models was limited due to numerical instability. In this study, the timestep control of the MPS method is revised by newly introducing particle number density control, which can efficiently reduce timestep to prevent instability when the crust is formed or breached in low viscous flow. The new method is successfully applied to ECOKATS-V1 spreading with different crust formations and breach conditions. Namely, with different Solidification Viscosity Threshold (SVT) and the Crust Fracture Stress Threshold (CFST) of the melt. The former determines the threshold viscosity above which the fluid is regarded as solid (crust). The latter determines the mechanical strength of the crust at the leading edge of the spreading front. There remain issues for future studies to further develop the method for more quantitative discussions.
AB - Understanding the ex-vessel spreading behavior of molten core materials (corium) on the reactor containment floor is of great importance for designing, managing, and evaluating severe accidents of light water reactors. Among some simulated ex-vessel corium spreading experiments, temporal termination and restart of the flow (stop-and-go) were highlighted in the ECOKATS-V1 experiment, in which the simulant oxide melt (consisted of 41% of Al2O3, 24% of SiO2, 19% of CaO, and 16% of FeO) was released into a 1-D channel, and the spreading behavior seemed to have temporarily stopped and restarted following crust formation and breach at the spreading leading edge. The preceding study developed crust formation and breach models for the Lagrangian-based Moving Particle Semi-Implicit (MPS) method to analyze such spreading. However, the applicability of the models was limited due to numerical instability. In this study, the timestep control of the MPS method is revised by newly introducing particle number density control, which can efficiently reduce timestep to prevent instability when the crust is formed or breached in low viscous flow. The new method is successfully applied to ECOKATS-V1 spreading with different crust formations and breach conditions. Namely, with different Solidification Viscosity Threshold (SVT) and the Crust Fracture Stress Threshold (CFST) of the melt. The former determines the threshold viscosity above which the fluid is regarded as solid (crust). The latter determines the mechanical strength of the crust at the leading edge of the spreading front. There remain issues for future studies to further develop the method for more quantitative discussions.
KW - Corium spreading
KW - Crust breach
KW - ECOKATS-V1
KW - MPS method
KW - Severe accident
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U2 - 10.1016/j.nucengdes.2021.111251
DO - 10.1016/j.nucengdes.2021.111251
M3 - Article
AN - SCOPUS:85105545189
SN - 0029-5493
VL - 379
JO - Nuclear Engineering and Design
JF - Nuclear Engineering and Design
M1 - 111251
ER -