Numerical study of initiating phase of core disruptive accident in small sodium-cooled fast reactors with negative void reactivity

石田 真也; 深野 義隆; 飛田 吉春; 岡野 靖

Journal of Nuclear Science and Technology, 13 Pages, 2023/00

https://doi.org/10.1080/00223131.2023.2243949

To improve the safety of future SFRs, the development of SFRs with low void reactivity has been promoted. Small SFRs can have a negative void coefficient of reactivity, so the analysis of the CDA event sequence in small SFRs is valuable for the investigation of the reactor characteristics for the future research and development of SFRs. In this study, the typical initiating events of a CDA in small SFRs were evaluated with the computational code, SAS4A. The event progression of ULOF and UTOP in the low void reactivity reactor is found to be slow due to the effective operation of the negative reactivity feedback and the absence of significant positive reactivity insertion. No power excursion occurs in the initiating phase. In ULOF, the cladding melt and relocation behavior becomes more important for the evaluation of the event progression due to its positive reactivity.

ナトリウム冷却金属燃料高速炉用炉心過渡挙動解析コード; EXCURSの改造と解析例

岡嶋 成晃; 軍司 康義*; 向山 武彦

JAERI-M 92-031, 81 Pages, 1992/03

JAERI-M-92-031.pdf:2.29MB

アクチノイド消滅処理専焼炉(ABR)の設計研究において、炉心過渡特性解析は安全性の観点から、重要である。そこで、Na冷却酸化物燃料高速炉用炉心過渡挙動解析コード「EXCURS」を、Na冷却金属燃料高速炉に適用できるように改造を行った。改造の妥当性を確認するために、ANLで行ったEBR-IIでの過渡試験解析結果や電中研で行った1000MWe級金属燃料高速炉の過渡特性解析結果と改造「EXCURS」の解析結果とを比較した。その結果、全般的に改造「EXCURS」の解析結果と他の解析結果は良い一致を示し、改造「EXCURS」がLMRやABRの炉心過渡現象を予測するのに使用できることが確認できた。改造「EXCURS」を用いて、Na冷却金属燃料専焼炉(M-ABR)のULOFおよびUTOP解析を実施した。さらに、安全性を検討するために、燃料の熱伝導率やフィードバック反応度係数のATWS解析結果に与える影響について、パラメータサーベイを行った。その結果、フラワリング係数、遅発中性子割合、燃料熱伝導率が燃料最高温度に強く影響することが分かった。

Exposure to X-rays enhances autophagy in human fibroblast cells

野口 実穂; 横谷 明徳; 鈴木 啓司*; 藤井 健太郎

no journal, , 

The exposure to ionizing radiation causes damage to not only DNA but also proteins or organelles in cytoplasm of cells. Recent studies report that, for most of normal human fibroblasts and some of solid carcinoma cells, cells exposed to ionizing radiation sustain irreversible growth arrest, but still maintain their viability with showing senescence character even though they might have severe DNA damage. These suggests that, in irradiated fibroblasts, intracellular degradation system "autophagy" eliminates accumulated damaged proteins or dysfunctional organelles to avoid induction of apoptosis. In this study, to clarify the role of autophagy on cell survival, we investigated change of autophagic activity in irradiated fibroblast cells in terms of escape from apoptosis. Induction of autophagy in normal human fibroblast BJ1-hTERT cells irradiated with 20 Gy X-rays were measured using the fluorescent probe, Cyto-ID Green, which stains specifically autophagic vacuoles. Irradiated cells were treated with Cyto-ID Green 15 min before observation. The cells observed by a fluorescent microscope were quantified as mean values of the fluorescent intensity per cell. Irradiated cells showed about 3 times higher induction of autophagic activity than non-irradiated cells at 24 h after irradiation. The activation of autophagy persisted for at least 5 days (120 h) after irradiation. These results strongly suggest that highly induced autophagy is involved in the elimination of damaged proteins and organelles to keep their physiological functions, and avoid apoptosis. Frequency of apoptosis is expected to increase if the autophagic pathway is blocked. Results will also be presented for the treatments with pharmacological agent inhibiting the autophagic process.