https://orcid.org/0000-0001-5880-355X
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Abstract
Accomplishing the retrieval of fuel debris from Fukushima Daiichi Nuclear Power Plant (1F) Unit 3 (1F3) requires an understanding of its distribution. In this study, we performed real-scale corium spreading and sedimentation behavior analyses using Lagrangian moving particle hydrodynamics and large eddy simulation methods. These methods allowed us to calculate the spreading of corium with various shear viscosities under water conditions and to propose the best estimation for the fuel debris distribution in 1F3. To minimize uncertainties arising from unknown boundary conditions, we investigated relevant parameters through literature review. Our analyses showed that highly viscous corium tends to pile up within the pedestal region under strong convective vapor and boiling heat transfer, while low-viscosity corium spreads to the outside of the pedestal regions regardless of cooling efficiency. We identified three cooling modes based on initial shear viscosity and cooling efficiency and predicted the fuel debris distribution in 1F3 by comparing our results to those of the Tokyo Electric Power Company (TEPCO) and Organisation for Economic Co-operation and Development/Nuclear Energy Agency (OECD/NEA) Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF) project. The distribution estimation of highly viscous corium derived from oxidic corium is consistent with the three-dimensional reconstructed image by TEPCO and the calculated results by the OECD/NEA BSAF project.
Acronyms
| BSAF: | = | Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station |
| CLADS: | = | Collaborative Laboratories for Advanced Decommissioning Science |
| CRD: | = | control rod drive |
| CREIPI: | = | Central Research Institute of Electric Power Industry |
| D/W: | = | dry well |
| IAE: | = | Institute of Applied Energy |
| IRSN: | = | Institute de radioprotection et de surete nucleaire |
| JAEA: | = | Japan Atomic Energy Agency |
| LES: | = | large eddy simulation |
| MCCI: | = | molten core–concrete interaction |
| MPH: | = | moving particle hydrodynamics |
| MPS: | = | moving particle semi-implicit (method) |
| NRA: | = | Nuclear Regulation Authority |
| OECD/NEA: | = | Organisation for Economic Co-operation and Development/Nuclear Energy Agency |
| PCV: | = | primary containment vessel |
| PSI: | = | Paul Scherrer Institute |
| RPV: | = | reactor pressure vessel |
| S/C: | = | supression chamber |
| SNL: | = | Sandia National Laboratories |
| SPS: | = | subparticle scale |
| SS316L: | = | Type 316L stainless steel |
| TC: | = | thermocouple |
| TEPCO: | = | Tokyo Electric Power Company |
| VTT: | = | Valtion Teknillinen Tutklimuskeskus |
| 1F: | = | Fukushima Daiichi Nuclear Power Plant |
| 1F1: | = | Fukushima Daiichi Nuclear Power Plant Unit 1 |
| 1F2: | = | Fukushima Daiichi Nuclear Power Plant Unit 2 |
| 1F3: | = | Fukushima Daiichi Nuclear Power Plant Unit 3 |
| 3-D: | = | three-dimensional |
Acknowledgments
Part of this research was conducted under the auspices of the Nuclear Energy Science and Technology and Human Resource Development Project sponsored by CLADS, JAEA. In addition, the authors would like to thank the Mitsubishi Heavy Industries committee members for their provision of the comments. This work was supported by Japan Society for the Promotion of Science [KAKENHI grant no. JP22J12786].
Disclosure Statement
No potential conflict of interest was reported by the author(s).
Correction Statement
This article has been corrected with minor changes. These changes do not impact the academic content of the article.