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Thermal properties of Three Mile Island Unit 2 core debris and simulated debris

TMI-2炉心デブリと模擬デブリの熱特性

永瀬 文久 ; 上塚 寛

Nagase, Fumihisa; Uetsuka, Hiroshi

シビアアクシデント時における炉心損傷を適切に解析するためには、溶融・混合した炉心材料の熱特性を調べる必要がある。TMI-2炉から採取したデブリとTMI-2デブリに似た化学組成と空孔率を持つ模擬デブリについて、潜熱,熱膨張率,熱拡散率,融点を測定あるいは推定した。おもに(U,Zr)O$$_{2}$$からなるTMI-2デブリの熱拡散率は、室温ではUO$$_{2}$$の10から25%であったが、1500K以上では同等であった。模擬デブリの融点は約2840Kであり、同じZrO$$_{2}$$/UO$$_{2}$$比を持つ(U,Zr)O$$_{2}$$の液相形成温度とほぼ同じであった。すなわち、デブリに含まれる重量比10%以下の他の炉心構成材料が溶融温度に及ぼす影響は非常に小さい。

Thermal properties of molten and mixed core materials are required to be known for effective analysis of core damage in severe accidents at nuclear power plants. The specific heat capacity, thermal expansion, thermal diffusivity, and melting temperature were measured or estimated on the core debris samples of the Three Mile Island Unit 2 (TMI-2) reactor and simulated debris (SIMDEBRIS), which had chemical composition and porosity similar to the TMI-2 debris. The thermal diffusivity of the TMI-2 debris, which is mainly composed of (U,Zr)O$$_{2}$$, was as low as 10% to 25% of UO$$_{2}$$ at room temperature but was comparable above 1500 K. The melting temperature of SIMDEBRIS was about 2840 K, which is equivalent to the liquidus temperature of (U,Zr)O$$_{2}$$ with the same ZrO$$_{2}$$/UO$$_{2}$$ ratio. Accordingly, other core materials less than 10% in weight were observed to have no influence on the melting temperature.

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パーセンタイル:55.88

分野:Nuclear Science & Technology

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