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New Approach for the Root Cause of Fukushima Meltdown Accident

Received: 5 December 2022     Accepted: 11 January 2023     Published: 21 March 2023
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Abstract

The purpose of this Commentary is to clarify as much as possible the whole history of reactor and containment pressure changes in the Fukushima meltdown accident. It is based on a new approach for film boiling, which is kept after the Zr-H2O reactions. Most important point of this approach is that the author applied film boiling based on boiling curve, which is basic theory in boiling phenomena, for the Fukushima accident phenomena. As the reaction rate is proportional to the reactor or containment pressure under film boiling, it increases rapidly and stops suddenly, keeping the film boiling. The containment pressure change consists of three phases, namely pressurizing, keeping the high pressure and de-pressurizing. The containment is pressurized by H2 gas and steam produced by the Zr-H2O reactions and de-pressurized by a heatsink such as the containment wall and inner shield concrete after reaction stops. The high pressure between these pressure changes is kept by balancing the H2 gas produced by reaction with the leaked gas from the gap between the top lid and the containment. Core decay heat is large, but its change is negligibly small. So, the pressurization is calculated from H2 gas and steam produced by the Zr- H2O reactions. The heatsink balances with the reaction during the high pressure condition. The de-pressurization occurs after the reaction is over, so the reaction heat rate can be calculated by the heat rate of the heatsink, which is equal to the condensation rate during de-pressurization. The leak rate of the leak gas can be calculated using the reaction rate. It is very important that the rection rate is slowed by the insufficient steam supply, as the melted reactor cores in the Fukushima accident were covered with H2 gas and steam (film boiling) at 0.8MPa or lower pressure. This is different from the rate (at approx. 7MPa) in the Three Mile Island accident, as the steam specific volume at 0.8 MPa is ten times larger than that at 7 MPa. The calculation results based on this assumption show that almost all the Zr in each core of Units 1, 2 and 3 reacted with water.

Published in International Journal of Science, Technology and Society (Volume 11, Issue 2)
DOI 10.11648/j.ijsts.20231102.14
Page(s) 62-73
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2023. Published by Science Publishing Group

Keywords

Fukushima Daiichi Nuclear Power Plant, Meltdown, Boiling Curve, Film Boiling, Steam Condensation, Zr-H2O Reaction, Containment Pressure

References
[1] Tokyo Electric Power Company (TEPCO) Fifth Progress Report (https://www.tepco.co.jp/en/decommision/accident/unsolved-e.html)
[2] Pool Boiling Curve - an overview | Science Direct Topics (https://www.sciencedirect.com/topics/engineering/pool boiling curve), (accessed on Oct. 08, 2021).
[3] Main Findings, Remaining Uncertainties and Lessons Learned from the OECD/NEA BSAF Project (https://doi.org/10.1080/00295450.2020.1724731).
[4] Control valves for steam, superheated steam: Calculation of Cv and mass flow (myengineeringtools.com) (https://www.hisaka.co.jp/valve/techDoc/techDoc01.html), (accessed on Oct. 09, 2021).
[5] Tsuruta et al., Geochemical Journal, 52, 2018.
[6] Tsuyoshi MTSUOKA, Trans. Atomic Energy Soc. Jpn., Vol. 20, p131-142 (2021).
[7] NRA Japan, Review and analysis meeting about Fukushima Daiichi Accident, the 32th Meeting (31 on November, 2022) Attachment 1-2 (Review for concrete found in PCV of Unit 1 by robot camera, Osaka University 1F-2050) (https://www.nra.go.jp/disclosure/committee/yuushikisya/jiko_bunseki01/).
[8] Journal of Nuclear Materials Volume 542, 15 December 2020, 152471 Morphology and phase distributions of molten core in a reactor vessel.
[9] Masaki Kurata, Trans. Atomic Energy Soc. Jpn., Vol. 65, No. 1 p13-18 (2023).
[10] Nuclear Engineering and Design Volume 403, March 2023, 112142, Development of PWR lower head failure model for severe accident analysis.
[11] Nuclear Engineering and Design Volume 392, June 2022, 111746 Evaluation of temperature and flow area variations through the fuel degradation and relocation of the SFD Test 1–4, Koji Nishida.
[12] Journal of Hazardous Materials Volume 428, 15 April 2022, 128214, Volatilization of B4C control rods in Fukushima Daiichi nuclear reactors during meltdown, Kazuki Fueda.
[13] Journal of Nuclear Materials Volume 572, 15 December 2022, 154040, Fission products chemistry in simulated PWR fuel up to 2100°C: Experimental characterization and TAF-ID modelling. E. Geiger.
[14] Journal of Nuclear Materials Volume 559, February 2022, 153415, Research on the nuclear fuel rods melting behaviors by alternative material experiments.
[15] Progress in Nuclear Energy Volume 108, September 2018, Pages 398-408, Results of simulant effect on large corium pool behavior based on COPRA facility.
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    Tsuyoshi Matsuoka. (2023). New Approach for the Root Cause of Fukushima Meltdown Accident. International Journal of Science, Technology and Society, 11(2), 62-73. https://doi.org/10.11648/j.ijsts.20231102.14

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    ACS Style

    Tsuyoshi Matsuoka. New Approach for the Root Cause of Fukushima Meltdown Accident. Int. J. Sci. Technol. Soc. 2023, 11(2), 62-73. doi: 10.11648/j.ijsts.20231102.14

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    AMA Style

    Tsuyoshi Matsuoka. New Approach for the Root Cause of Fukushima Meltdown Accident. Int J Sci Technol Soc. 2023;11(2):62-73. doi: 10.11648/j.ijsts.20231102.14

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  • @article{10.11648/j.ijsts.20231102.14,
      author = {Tsuyoshi Matsuoka},
      title = {New Approach for the Root Cause of Fukushima Meltdown Accident},
      journal = {International Journal of Science, Technology and Society},
      volume = {11},
      number = {2},
      pages = {62-73},
      doi = {10.11648/j.ijsts.20231102.14},
      url = {https://doi.org/10.11648/j.ijsts.20231102.14},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ijsts.20231102.14},
      abstract = {The purpose of this Commentary is to clarify as much as possible the whole history of reactor and containment pressure changes in the Fukushima meltdown accident. It is based on a new approach for film boiling, which is kept after the Zr-H2O reactions. Most important point of this approach is that the author applied film boiling based on boiling curve, which is basic theory in boiling phenomena, for the Fukushima accident phenomena. As the reaction rate is proportional to the reactor or containment pressure under film boiling, it increases rapidly and stops suddenly, keeping the film boiling. The containment pressure change consists of three phases, namely pressurizing, keeping the high pressure and de-pressurizing. The containment is pressurized by H2 gas and steam produced by the Zr-H2O reactions and de-pressurized by a heatsink such as the containment wall and inner shield concrete after reaction stops. The high pressure between these pressure changes is kept by balancing the H2 gas produced by reaction with the leaked gas from the gap between the top lid and the containment. Core decay heat is large, but its change is negligibly small. So, the pressurization is calculated from H2 gas and steam produced by the Zr- H2O reactions. The heatsink balances with the reaction during the high pressure condition. The de-pressurization occurs after the reaction is over, so the reaction heat rate can be calculated by the heat rate of the heatsink, which is equal to the condensation rate during de-pressurization. The leak rate of the leak gas can be calculated using the reaction rate. It is very important that the rection rate is slowed by the insufficient steam supply, as the melted reactor cores in the Fukushima accident were covered with H2 gas and steam (film boiling) at 0.8MPa or lower pressure. This is different from the rate (at approx. 7MPa) in the Three Mile Island accident, as the steam specific volume at 0.8 MPa is ten times larger than that at 7 MPa. The calculation results based on this assumption show that almost all the Zr in each core of Units 1, 2 and 3 reacted with water.},
     year = {2023}
    }
    

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  • TY  - JOUR
    T1  - New Approach for the Root Cause of Fukushima Meltdown Accident
    AU  - Tsuyoshi Matsuoka
    Y1  - 2023/03/21
    PY  - 2023
    N1  - https://doi.org/10.11648/j.ijsts.20231102.14
    DO  - 10.11648/j.ijsts.20231102.14
    T2  - International Journal of Science, Technology and Society
    JF  - International Journal of Science, Technology and Society
    JO  - International Journal of Science, Technology and Society
    SP  - 62
    EP  - 73
    PB  - Science Publishing Group
    SN  - 2330-7420
    UR  - https://doi.org/10.11648/j.ijsts.20231102.14
    AB  - The purpose of this Commentary is to clarify as much as possible the whole history of reactor and containment pressure changes in the Fukushima meltdown accident. It is based on a new approach for film boiling, which is kept after the Zr-H2O reactions. Most important point of this approach is that the author applied film boiling based on boiling curve, which is basic theory in boiling phenomena, for the Fukushima accident phenomena. As the reaction rate is proportional to the reactor or containment pressure under film boiling, it increases rapidly and stops suddenly, keeping the film boiling. The containment pressure change consists of three phases, namely pressurizing, keeping the high pressure and de-pressurizing. The containment is pressurized by H2 gas and steam produced by the Zr-H2O reactions and de-pressurized by a heatsink such as the containment wall and inner shield concrete after reaction stops. The high pressure between these pressure changes is kept by balancing the H2 gas produced by reaction with the leaked gas from the gap between the top lid and the containment. Core decay heat is large, but its change is negligibly small. So, the pressurization is calculated from H2 gas and steam produced by the Zr- H2O reactions. The heatsink balances with the reaction during the high pressure condition. The de-pressurization occurs after the reaction is over, so the reaction heat rate can be calculated by the heat rate of the heatsink, which is equal to the condensation rate during de-pressurization. The leak rate of the leak gas can be calculated using the reaction rate. It is very important that the rection rate is slowed by the insufficient steam supply, as the melted reactor cores in the Fukushima accident were covered with H2 gas and steam (film boiling) at 0.8MPa or lower pressure. This is different from the rate (at approx. 7MPa) in the Three Mile Island accident, as the steam specific volume at 0.8 MPa is ten times larger than that at 7 MPa. The calculation results based on this assumption show that almost all the Zr in each core of Units 1, 2 and 3 reacted with water.
    VL  - 11
    IS  - 2
    ER  - 

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Author Information
  • Mechanical Engineering, Kyushu University, Kobe City, Japan

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