TY - JOUR
T1 - Sensitivity analysis of core slumping and debris quenching behavior of Fukushima Daiichi Unit-3 accident
AU - Li, Xin
AU - Sato, Ikken
AU - Yamaji, Akifumi
AU - Regalado, Mariko
AU - Wang, Jun
N1 - Funding Information:
The authors would like to express their great gratitude to Dr. Randall Gauntt and Dr. Nathan Andrews from Sandia National Laboratories for their kind support on MELCOR code during this research. Special thanks were given to Mr. Tuomo Sevón at VTT Technical Research Centre of Finland for kindly sharing his input data for MELCOR code attached to reference (Sevón, 2015) and his expertise that has greatly inspired and assisted the authors for this work. Part of this work was conducted in “Estimation of the In-Depth Debris Status of Fukushima Unit-2 and Unit-3 with Multi-Physics Modeling”, supported by Nuclear Energy Science & Technology and Human Resource Development Project of Japan. Part of this work was conducted under “Understanding Mechanisms of Severe Accidents and Improving Safety of Nuclear Reactors by Computer Science” of Institute for Advanced Theoretical and Experimental Physics and Waseda Research Institute for Science and Engineering.
Funding Information:
The authors would like to express their great gratitude to Dr. Randall Gauntt and Dr. Nathan Andrews from Sandia National Laboratories for their kind support on MELCOR code during this research. Special thanks were given to Mr. Tuomo Sev?n at VTT Technical Research Centre of Finland for kindly sharing his input data for MELCOR code attached to reference (Sev?n, 2015) and his expertise that has greatly inspired and assisted the authors for this work. Part of this work was conducted in ?Estimation of the In-Depth Debris Status of Fukushima Unit-2 and Unit-3 with Multi-Physics Modeling?, supported by Nuclear Energy Science & Technology and Human Resource Development Project of Japan. Part of this work was conducted under ?Understanding Mechanisms of Severe Accidents and Improving Safety of Nuclear Reactors by Computer Science? of Institute for Advanced Theoretical and Experimental Physics and Waseda Research Institute for Science and Engineering.
Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2021/1
Y1 - 2021/1
N2 - The Great East Japan earthquake and the subsequent tsunami which occurred on March 11th, 2011 put the operating Units 1–3 at Fukushima Daiichi Nuclear Power Plant (NPP) in severe accident conditions and core meltdown due to station blackout. Although research efforts have been made by various parties to study the accident scenarios since the Fukushima accident, there remain unresolved issues regarding the core degradation behavior suggested by measurement data such as water level, Reactor Pressure Vessel (RPV) pressure and Primary Containment Vessel (PCV) pressure. To analyze and resolve such issues would be helpful to promote further understanding of the severe accident scenario at Fukushima units as well as the decommissioning work undergoing. The current study focuses on a detailed analysis of the RPV pressure peak event that occurred in Unit-3 at 12:00 on March 13th 2011. Sensitivity analysis cases were carried out with MELCOR 2.2 code i with sensitivity parameters that can influence the RPV pressure behavior, such as the debris quenching heat transfer coefficient, the number of opening SRVs during the RPV pressure peak event, amount of core slumping and particulate debris diameter. The cases that could reproduce the RPV pressure peak were further discussed to show likely debris bed energy history and the water mass history in the lower plenum during the RPV pressure peak event. The current study suggests that 1) Opening of SRVs equivalent to the total area of 4–6 fully-open SRVs (or equivalent leak area) could have occurred during the pressurization phase of the RPV accompanied by heavy debris quenching effect, while the opening of SRVs equivalent to a total area of at least 2 fully-open SRVs (or equivalent leak area) could have occurred during the depressurization phase of the RPV accompanied by moderate debris quenching effect. 2) The particulate debris diameter is not a very sensitive parameter when evaluating the debris quenching effect of Unit-3 in the current MELCOR modeling. 3) The current modeling suggests that around 70–110 GJ of energy can be removed by coolant during the debris quenching period with 30 tons of water reduction from the lower plenum.
AB - The Great East Japan earthquake and the subsequent tsunami which occurred on March 11th, 2011 put the operating Units 1–3 at Fukushima Daiichi Nuclear Power Plant (NPP) in severe accident conditions and core meltdown due to station blackout. Although research efforts have been made by various parties to study the accident scenarios since the Fukushima accident, there remain unresolved issues regarding the core degradation behavior suggested by measurement data such as water level, Reactor Pressure Vessel (RPV) pressure and Primary Containment Vessel (PCV) pressure. To analyze and resolve such issues would be helpful to promote further understanding of the severe accident scenario at Fukushima units as well as the decommissioning work undergoing. The current study focuses on a detailed analysis of the RPV pressure peak event that occurred in Unit-3 at 12:00 on March 13th 2011. Sensitivity analysis cases were carried out with MELCOR 2.2 code i with sensitivity parameters that can influence the RPV pressure behavior, such as the debris quenching heat transfer coefficient, the number of opening SRVs during the RPV pressure peak event, amount of core slumping and particulate debris diameter. The cases that could reproduce the RPV pressure peak were further discussed to show likely debris bed energy history and the water mass history in the lower plenum during the RPV pressure peak event. The current study suggests that 1) Opening of SRVs equivalent to the total area of 4–6 fully-open SRVs (or equivalent leak area) could have occurred during the pressurization phase of the RPV accompanied by heavy debris quenching effect, while the opening of SRVs equivalent to a total area of at least 2 fully-open SRVs (or equivalent leak area) could have occurred during the depressurization phase of the RPV accompanied by moderate debris quenching effect. 2) The particulate debris diameter is not a very sensitive parameter when evaluating the debris quenching effect of Unit-3 in the current MELCOR modeling. 3) The current modeling suggests that around 70–110 GJ of energy can be removed by coolant during the debris quenching period with 30 tons of water reduction from the lower plenum.
KW - BWR
KW - Fukushima Daichi Nuclear Power PLant
KW - Sensitivity analysis
KW - Severe accident
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U2 - 10.1016/j.anucene.2020.107819
DO - 10.1016/j.anucene.2020.107819
M3 - Article
AN - SCOPUS:85090556622
SN - 0306-4549
VL - 150
JO - Annals of Nuclear Energy
JF - Annals of Nuclear Energy
M1 - 107819
ER -