2022 Fiscal Year Final Research Report
Study on verification of effectiveness of molten core cooling by mitigation measures in severe accident
| Project/Area Number |
19K05322
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 31010:Nuclear engineering-related
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| Research Institution | Hokkaido University |
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Principal Investigator |
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | 原子炉過酷事故 / デブリベッド / 沸騰伝熱 / 限界熱流束 |
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| Outline of Final Research Achievements |
In order to investigate the cooling characteristics of the molten core by pre-flooding with water in the containment vessel, which is a mitigation measure for severe accidents in light water reactors, experiments were conducted on the critical heat flux (CHF) in a boiling configuration in which heat-generating particles simulating solidified debris dispersed in water were deposited on a heating surface simulating a solidified crust layer on the molten-core pool surface. The results show that the CHF decreases monotonically with the heat generation rate of the particulate beds when the particle size is less than 1 mm, as predicted by previous models, while the CHF is independent of the heat generation rate of the particulate beds when the particle size is greater than 3 mm. These results suggest that the effectiveness of severe accident mitigation measures by pre-flooding in the containment vessel depends on the particle size, and may be effective for particle sizes larger than 3 mm.
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| Free Research Field |
原子炉熱工学
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| Academic Significance and Societal Importance of the Research Achievements |
軽水炉の過酷事故時に格納容器に事前水張りをする過酷事故緩和策の有効性を検証するためには，溶融炉心プール上面に形成される固化クラスト上に，水中で分散した粒子状デブリが堆積した状況でのクラスト面上の限界熱流束(CHF)の挙動が重要となる．既往のモデルでは，CHFは粒子層の発熱量の増加とともに単調に減少するため緩和策は成立しないと予測する．しかし，本研究の結果，CHFの特性は粒子径によって異なり，粒径が3mm以上ではCHFは粒子層の発熱量に依存しないことが判明した．したがって，事前水張による緩和策はクラスト面上への堆積デブリ径が3mm以上の場合は有効であることが判明した．
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