Abstract
To retrieve the fuel debris in Fukushima Daiichi Nuclear Power Plants (1F), it is essential to infer the fuel debris distribution. In particular, the molten metal spreading behavior is one of the vital phenomena in nuclear severe accidents because it determines the initial condition for further accident scenarios such as molten core concrete interaction (MCCI). In this study, the fundamental molten metal spreading experiments were performed with different outlet diameters and sample amounts to investigate the effect of the outlet for spreading-solidification behavior. In the numerical analysis, the moving particle full-implicit method (MPFI), which is one of the particle methods, was applied to simulate the spreading experiments. In the MPFI framework, the melting-solidification model including heat transfer, radiation heat loss, phase change, and solid fraction-dependent viscosity was developed and implemented. In addition, the difference in the spreading and solidification behavior due to the outlet diameters was reproduced in the calculation. The simulation results reveal the detailed solidification procedure during the molten metal spreading. It is found that the viscosity change and the solid fraction change during the spreading are key factors for the free surface condition and solidified materials. Overall, it is suggested that the MPFI method has the potential to simulate the actual nuclear melt-down phenomena in the future.
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Abbreviations
- A :
-
Surface area of particle
- C ps :
-
Specific heat for solid/(J·(kg·K)−1)
- C pl :
-
Specific heat for liquid/(J·(kg·K)−1)
- D :
-
Nozzle diameter/mm
- M :
-
Molten metal amount/g
- MPFI:
-
Moving particle Full-implicit method
- MPS:
-
Moving particle Semi-implicit method
- Nu :
-
Nusselt number
- P :
-
Pressure/Pa
- Pr :
-
Prandtl number
- Q :
-
Heat source/J
- Re :
-
Reynolds number
- T :
-
Temperature/°C
- T e :
-
Environment temperature/°C
- T m :
-
Melting temperature/°C
- T s :
-
Stainless steel temperature/°C
- X :
-
Falling height/mm
- a :
-
Parameter for surface tension calculation
- d ij :
-
Distance between particle i and particle j/m
- g :
-
Gravity acceleration/(m·s−2)
- h :
-
Enthalpy/J
- h 1 :
-
Liquefying enthalpy/J
- h 0 :
-
Solidifying enthalpy/J
- k :
-
Thermal conductivity/(W·(m·K)−1)
- q radiation :
-
Heat flux from radiation/(W·m−2)
- r e :
-
Effective radius/m
- t :
-
Time/s
- u :
-
Fluid velocity/(m·s−1)
- w ij :
-
Weight function
- γ :
-
Solid fraction
- η :
-
Emissivity
- κ :
-
Compressibility/(N·m−2)
- μ 0 :
-
Initial viscosity/(Pa·s)
- μ 1 :
-
Viscosity/(Pa·s)
- ρ :
-
Density/(kg·m−3)
- σ :
-
Stephan-Boltzmann constant
- ω :
-
Angular velocity/(rad·s−1)
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This study was partially supported by the Mitsubishi Heavy Industry (MHI).
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Yokoyama, R., Kondo, M., Suzuki, S. et al. Analysis of molten metal spreading and solidification behaviors utilizing moving particle full-implicit method. Front. Energy 15, 959–973 (2021). https://doi.org/10.1007/s11708-021-0753-0
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DOI: https://doi.org/10.1007/s11708-021-0753-0